@niivue/niivue/src/shader-srcs.ts

minimal webgl2 nifti image viewer

export const vertRenderShader = `#version 300 es
#line 4
layout(location=0) in vec3 pos;
layout(location=1) in vec3 texCoords;
uniform mat4 mvpMtx;
out vec3 vColor;
void main(void) {
	gl_Position = mvpMtx * vec4(pos, 1.0);
	vColor = texCoords;
}`

const kDrawFunc = `
	vec4 drawColor(float scalar, float drawOpacity) {
		float nlayer = float(textureSize(colormap, 0).y);
		float layer = (nlayer - 0.5) / nlayer;
		vec4 dcolor = texture(colormap, vec2((scalar * 255.0)/256.0 + 0.5/256.0, layer)).rgba;
		dcolor.a *= drawOpacity;
		return dcolor;
}`

const kRenderFunc =
    `vec3 GetBackPosition(vec3 startPositionTex) {
	vec3 startPosition = startPositionTex * volScale;
	vec3 invR = 1.0 / rayDir;
	vec3 tbot = invR * (vec3(0.0)-startPosition);
	vec3 ttop = invR * (volScale-startPosition);
	vec3 tmax = max(ttop, tbot);
	vec2 t = min(tmax.xx, tmax.yz);
	vec3 endPosition = startPosition + (rayDir * min(t.x, t.y));
	//convert world position back to texture position:
	endPosition = endPosition / volScale;
	return endPosition;
}

float distance2Plane(in vec4 samplePos, in vec4 clipPlane) {
	// treat clipPlane.a > 1 as "no clip" sentinel (keeps existing behavior)
	if (clipPlane.a > 1.0) {
			return 1000.0; // sentinel large distance
	}
	vec3 n = clipPlane.xyz;
	const float EPS = 1e-6;
	float nlen = length(n);
	if (nlen < EPS) {
			return 1000.0; // invalid plane normal
	}
	// signed plane value: dot(n, p-0.5) + a
	float signedDist = dot(n, samplePos.xyz - 0.5) + clipPlane.a;
	// perpendicular (Euclidean) distance is |signedDist| / |n|
	return abs(signedDist) / nlen;
}

// see if clip plane trims ray sampling range sampleStartEnd.x..y
void clipSampleRange(in vec3 dir, in vec4 rayStart, in vec4 clipPlane, inout vec2 sampleStartEnd, inout bool hasClip) {
	const float CSR_EPS = 1e-6;
	// quick exit: no clip plane
	if (clipPlane.a > 1.0)
			return;
	hasClip = true;
	// quick exit: empty range
	if ((sampleStartEnd.y - sampleStartEnd.x) <= CSR_EPS)
			return;
	// Which side does the ray start on? (plane eqn: dot(n, p-0.5) + a = 0)
	float sampleSide = dot(clipPlane.xyz, rayStart.xyz - 0.5) + clipPlane.a;
	bool startsFront = (sampleSide < 0.0);
	float dis = - 1.0;
	// plane normal dot ray direction
	float cdot = dot(dir, clipPlane.xyz);
	// avoid division by 0 for near-parallel plne
	if (abs(cdot) >= CSR_EPS)
		dis = (-clipPlane.a - dot(clipPlane.xyz, rayStart.xyz - 0.5)) / cdot;
	if (dis < 0.0 || dis > sampleStartEnd.y + CSR_EPS) {
			if (startsFront)
				sampleStartEnd = vec2(0.0, 0.0);
			return;
	}
	bool frontface = (cdot > 0.0);
	if (frontface)
		sampleStartEnd.x = max(sampleStartEnd.x, dis);
	else
		sampleStartEnd.y = min(sampleStartEnd.y, dis);
	// if nothing remains, mark empty
	if (sampleStartEnd.y - sampleStartEnd.x <= CSR_EPS)
		sampleStartEnd = vec2(0.0, 0.0);
}

bool skipSample (float pos, vec2 sampleRange) {
	return (pos < sampleRange.x || pos > sampleRange.y);
}

float frac2ndc(vec3 frac) {
//https://stackoverflow.com/questions/7777913/how-to-render-depth-linearly-in-modern-opengl-with-gl-fragcoord-z-in-fragment-sh
	vec4 pos = vec4(frac.xyz, 1.0); //fraction
	vec4 dim = vec4(vec3(textureSize(volume, 0)), 1.0);
	pos = pos * dim;
	vec4 shim = vec4(-0.5, -0.5, -0.5, 0.0);
	pos += shim;
	vec4 mm = transpose(matRAS) * pos;
	float z_ndc = (mvpMtx * vec4(mm.xyz, 1.0)).z;
	return (z_ndc + 1.0) / 2.0;
}` + kDrawFunc

const kRenderInit = `void main() {
	if (fColor.x > 2.0) {
		fColor = vec4(1.0, 0.0, 0.0, 0.5);
		return;
	}
	fColor = vec4(0.0,0.0,0.0,0.0);
	vec4 clipPlaneColorX = clipPlaneColor;
	//if (clipPlaneColor.a < 0.0)
	//	clipPlaneColorX.a = - 1.0;
	bool isColorPlaneInVolume = false;
	if (clipPlaneColorX.a < 0.0) {
		isColorPlaneInVolume = true;
		clipPlaneColorX.a = 0.0;
	}
	//fColor = vec4(vColor.rgb, 1.0); return;
	vec3 start = vColor;
	gl_FragDepth = 1.0;
	vec3 backPosition = GetBackPosition(start);
	// fColor = vec4(backPosition, 1.0); return;
	vec3 dir = normalize(backPosition - start);
	//clipVolumeStart(start, backPosition);
	dir = normalize(dir);
	float len = length(backPosition - start);
	float lenVox = length((texVox * start) - (texVox * backPosition));
	if ((lenVox < 0.5) || (len > 3.0)) { //length limit for parallel rays
		return;
	}
	float sliceSize = len / lenVox; //e.g. if ray length is 1.0 and traverses 50 voxels, each voxel is 0.02 in unit cube
	float stepSize = sliceSize; //quality: larger step is faster traversal, but fewer samples
	float opacityCorrection = stepSize/sliceSize;
	vec4 deltaDir = vec4(dir.xyz * stepSize, stepSize);
	vec4 samplePos = vec4(start.xyz, 0.0); //ray position

	vec2 sampleRange = vec2(0.0, len);
	bool hasClip = false;
	for (int i = 0; i < MAX_CLIP_PLANES; i++)
		clipSampleRange(dir, samplePos, clipPlanes[i], sampleRange, hasClip);
	bool isClip = (sampleRange.x > 0.0) || ((sampleRange.y < len) && (sampleRange.y > 0.0));
	float stepSizeFast = sliceSize * 1.9;
	vec4 deltaDirFast = vec4(dir.xyz * stepSizeFast, stepSizeFast);
	if ((isClipCutaway) && (sampleRange.x <= 0.0) && (sampleRange.y >= len)) {
		//completely clipped, but ray does not intersect plane
		if (hasClip)
			samplePos.a = len + 1.0;
		else
			sampleRange = vec2(0.0, 0.0);
	}
	if ((!isClipCutaway) && (sampleRange.x >= sampleRange.y))
		samplePos.a = len + 1.0;
	while (samplePos.a <= len) {
		if (skipSample(samplePos.a, sampleRange) ^^ isClipCutaway) {
			samplePos += deltaDirFast;
			continue;
		}
		float val = texture(volume, samplePos.xyz).a;
		if (val > 0.01)
			break;
		samplePos += deltaDirFast; //advance ray position
	}
	float drawOpacityA = renderDrawAmbientOcclusionXY.y;
	if ((samplePos.a >= len) && (((overlays < 1.0) && (drawOpacityA <= 0.0) ) || (backgroundMasksOverlays > 0)))  {
		if (isClip)
			fColor += clipPlaneColorX;
		return;
	}
	fColor = vec4(1.0, 1.0, 1.0, 1.0);
	//gl_FragDepth = frac2ndc(samplePos.xyz); //crude due to fast pass resolution
	if (samplePos.a > deltaDirFast.a )
		samplePos -= deltaDirFast;
	//end: fast pass
	vec4 colAcc = vec4(0.0,0.0,0.0,0.0);
	vec4 firstHit = vec4(0.0,0.0,0.0,2.0 * len);
	const float earlyTermination = 0.95;
	float backNearest = len; //assume no hit
	float ran = fract(sin(gl_FragCoord.x * 12.9898 + gl_FragCoord.y * 78.233) * 43758.5453);
	// clip planes create steep gradients: reduce aliasing with more jitter
	if (isClip)
		samplePos += deltaDir * ran * 1.41; //jitter ray
	else
		samplePos += deltaDir * ran; //jitter ray
	vec2 overlaySampleRange = isClipAllVolumes ? sampleRange : vec2(0.0, len);
	bool overlayIsClipCutaway = isClipAllVolumes && isClipCutaway;
`

const kRenderTail = `
	if (firstHit.a < len) {
		gl_FragDepth = frac2ndc(firstHit.xyz);
		vec4 paqdSample = texture(paqd, samplePos.xyz);
		if (paqdSample.a > 0.0) {
			//colAcc.rgb = paqdSample.rgb;
			float a = max(abs(paqdUniforms[2]), abs(paqdUniforms[3]));
			colAcc.rgb = mix(colAcc.rgb, paqdSample.rgb, 0.5 * paqdSample.a * a);
		}
		if (isClip) {
			//shade voxels with clip color
			if (clipPlaneColor.a < 0.0) {
					float thresh = 4.0 * sliceSize;
					float firstHit1 = firstHit.a + deltaDir.a;
				if (isClipCutaway) {
					float min1 = abs(firstHit1 - sampleRange.y);
					float dx = samplePos.a - firstHit1;
					if (min1 < thresh)
						colAcc.rgb = mix(colAcc.rgb, clipPlaneColorX.rgb, abs(clipPlaneColor.a));
					else if (( colAcc.a > earlyTermination ) && (dx > thresh)) {
						min1 = abs(firstHit1 - sampleRange.x);
						if (min1 < (thresh * 0.5)) {
							colAcc.rgb = mix(colAcc.rgb , clipPlaneColorX.rgb, abs(clipPlaneColor.a)*0.5);
						}
							
					}
				} else {
					if (abs(firstHit1 - sampleRange.x) < thresh)
						colAcc.rgb = mix(colAcc.rgb, clipPlaneColorX.rgb, abs(clipPlaneColor.a));
				} // clipPlaneColor.a < 0.0
			}
			//ambient occlusion: make creases dark
			float min1 = 1000.0;
			float min2 = 1000.0;
			// find smallest and second-smallest distances
			vec4 firstHit1 = firstHit - deltaDir;
			for (int i = 0; i < MAX_CLIP_PLANES; i++) {
				float d = distance2Plane(firstHit1, clipPlanes[i]);
				if (d < min1) {
						min2 = min1;
						min1 = d;
				} else if (d < min2) {
						min2 = d;
				}
			}
			float thresh = 1.2 * sliceSize;
			if ((isClipCutaway) && (min2 < thresh) && (sampleRange.x > 0.0)) {
				if ((abs(sampleRange.x - firstHit.a) > ( 2.0 * thresh)) && ((abs(sampleRange.y - firstHit.a) > (2.0 * thresh))))
					min2 = thresh; 
			}
			// if second is 0 -> factor 0 (black), if second >= sliceSize -> factor 1 (unchanged)
			const float aoFrac = 0.5;
			float factor = (1.0 - aoFrac) + aoFrac * clamp(min2 / thresh, 0.0, 1.0);
			// linear darkening: multiply color by factor (or use mix(vec3(0), colAcc.rgb, factor))
			colAcc.rgb *= factor;
		}
	}
	colAcc.a = (colAcc.a / earlyTermination) * backOpacity;
	fColor = colAcc;
	float renderDrawAmbientOcclusionX = renderDrawAmbientOcclusionXY.x;
	float drawOpacity = renderDrawAmbientOcclusionXY.y;
	if ((overlays < 1.0) && (drawOpacity <= 0.0))
		return;
	//overlay pass
	samplePos = vec4(start.xyz, 0.0); //ray position
	//start: OPTIONAL fast pass: rapid traversal until first hit
	stepSizeFast = sliceSize * 1.0;
	deltaDirFast = vec4(dir.xyz * stepSizeFast, stepSizeFast);
	while (samplePos.a <= len) {
		if (skipSample(samplePos.a, overlaySampleRange) ^^ overlayIsClipCutaway) {
			samplePos += deltaDirFast;
			continue;
		}
		float val = texture(overlay, samplePos.xyz).a;
		if (drawOpacity > 0.0) {
			if (smoothDrawing > 0.0) {
				if (!isClipAllVolumes || !(skipSample(samplePos.a, sampleRange) ^^ isClipCutaway))
					val = max(val, texture(drawSmoothed, samplePos.xyz).r * 2.0);
			} else
				val = max(val, texture(drawing, samplePos.xyz).r);
		}
		if (val > 0.001)
			break;
		samplePos += deltaDirFast; //advance ray position
	}
	if (samplePos.a >= len) {
		if (isClip && (fColor.a == 0.0))
				fColor += clipPlaneColorX;
			return;
	}
	samplePos -= deltaDirFast;
	if (samplePos.a < 0.0)
		vec4 samplePos = vec4(start.xyz, 0.0); //ray position
	//end: fast pass
	float overFarthest = len;
	colAcc = vec4(0.0, 0.0, 0.0, 0.0);

	samplePos += deltaDir * ran; //jitter ray
	vec4 overFirstHit = vec4(0.0,0.0,0.0,2.0 * len);
	if (backgroundMasksOverlays > 0)
		samplePos = firstHit;
	bool firstDraw = true;
	// Hoist per-ray constants used by the smooth drawing path.
	vec3 vxSize = 1.0 / vec3(textureSize(drawing, 0));
	vec3 nRayDir = normalize(rayDir);
	// For smooth drawing with a clip plane: if the ray enters the unclipped region
	// already inside the drawn volume, start with prevSmoothOut=false so no
	// outside→inside transition is detected, suppressing the clip-plane cap face.
	bool prevSmoothOut = true;
	bool enteredFromOutside = false;
	vec4 cachedSmoothColor = vec4(0.0);
	if (isClipAllVolumes && isClip && !isClipCutaway && smoothDrawing > 0.0) {
		vec3 clipEntry = start.xyz + dir * sampleRange.x;
		if (texture(drawSmoothed, clipEntry).r >= 0.5)
			prevSmoothOut = false;
	}
	while (samplePos.a <= len) {
		if (skipSample(samplePos.a, overlaySampleRange) ^^ overlayIsClipCutaway) {
			samplePos += deltaDirFast;
			continue;
		}
		vec4 colorSample = texture(overlay, samplePos.xyz);
		if ((colorSample.a < 0.01) && (drawOpacity > 0.0)) {
			if (smoothDrawing > 0.0) {
				// Smooth drawing: isosurface rendering with gradient-based shading
				// Clip the smooth surface only when isClipAllVolumes is set
				if (isClipAllVolumes && (skipSample(samplePos.a, sampleRange) ^^ isClipCutaway)) {
					samplePos += deltaDir;
					continue;
				}
				float smoothVal = texture(drawSmoothed, samplePos.xyz).r;
				bool nowSmoothInside = (smoothVal > 0.5);
				// Track entry transitions: only mark enteredFromOutside on a genuine
				// outside→inside crossing; clear it when we exit.
				if (!nowSmoothInside) {
					prevSmoothOut = true;
					enteredFromOutside = false;
				} else if (prevSmoothOut) {
					// First inside sample: compute gradient, pen color, and Phong shading
					// once and cache the result for all subsequent interior steps.
					prevSmoothOut = false;
					enteredFromOutside = true;
					float gx = texture(drawSmoothed, samplePos.xyz + vec3(vxSize.x, 0.0, 0.0)).r
					         - texture(drawSmoothed, samplePos.xyz - vec3(vxSize.x, 0.0, 0.0)).r;
					float gy = texture(drawSmoothed, samplePos.xyz + vec3(0.0, vxSize.y, 0.0)).r
					         - texture(drawSmoothed, samplePos.xyz - vec3(0.0, vxSize.y, 0.0)).r;
					float gz = texture(drawSmoothed, samplePos.xyz + vec3(0.0, 0.0, vxSize.z)).r
					         - texture(drawSmoothed, samplePos.xyz - vec3(0.0, 0.0, vxSize.z)).r;
					vec3 grad = vec3(gx, gy, gz);
					float gradLen = length(grad);
					vec3 normal = gradLen > 0.001 ? normalize(grad) : vec3(0.0, 0.0, 1.0);
					// Get pen color from original drawing texture.
					float drawVal = texture(drawing, samplePos.xyz).r;
					if (drawVal == 0.0) {
						// Between painted voxels: step inward along the gradient
						// to find the nearest painted voxel's pen color.
						// (normal points inward toward higher smooth values)
						for (int k = 1; k <= 8; k++) {
							drawVal = texture(drawing, samplePos.xyz + normal * vxSize * float(k)).r;
							if (drawVal > 0.0) break;
						}
					}
					vec4 draw = drawColor(max(drawVal, 1.0 / 255.0), drawOpacity);
					// Phong shading with two-sided lighting.
					float NdotL = abs(dot(normal, nRayDir));
					vec3 reflected = reflect(nRayDir, normal);
					float spec = pow(max(dot(reflected, -nRayDir), 0.0), 20.0);
					draw.rgb *= (0.4 + 0.6 * NdotL);
					draw.rgb += vec3(0.2 * spec);
					cachedSmoothColor = draw;
				}
				// Use the cached shaded color for every interior step.
				if (nowSmoothInside && enteredFromOutside) {
					colorSample = cachedSmoothColor;
				}
			} else {
				// Original discrete drawing path
				float val = texture(drawing, samplePos.xyz).r;
				vec4 draw = drawColor(val, drawOpacity);
				if ((draw.a > 0.0) && (firstDraw)) {
				firstDraw = false;
				float sum = 0.0;
				const float mn = 1.0 / 256.0;
				const float sampleRadius = 1.1;
				float dx = sliceSize * sampleRadius;
				vec3 center = samplePos.xyz;
				//six neighbors that share a face
				sum += min(texture(drawing, center.xyz + cross(vec3(0.0,0.0,+dx), dir)).r, mn);
				sum += min(texture(drawing, center.xyz + cross(vec3(0.0,0.0,-dx), dir)).r, mn);
				sum += min(texture(drawing, center.xyz + cross(vec3(0.0,+dx,0.0), dir)).r, mn);
				sum += min(texture(drawing, center.xyz + cross(vec3(0.0,-dx,0.0), dir)).r, mn);
				sum += min(texture(drawing, center.xyz + cross(vec3(+dx,0.0,0.0), dir)).r, mn);
				sum += min(texture(drawing, center.xyz + cross(vec3(-dx,0.0,0.0), dir)).r, mn);
				//float proportion = (sum / mn) / 6.0;
				
				//12 neighbors that share an edge
				dx = sliceSize * sampleRadius * sqrt(2.0) * 0.5;
				sum += min(texture(drawing, center.xyz + cross(vec3(0.0,+dx,+dx), dir)).r, mn);
				sum += min(texture(drawing, center.xyz + cross(vec3(+dx,0.0,+dx), dir)).r, mn);
				sum += min(texture(drawing, center.xyz + cross(vec3(+dx,+dx,0.0), dir)).r, mn);
				sum += min(texture(drawing, center.xyz + cross(vec3(0.0,-dx,-dx), dir)).r, mn);
				sum += min(texture(drawing, center.xyz + cross(vec3(-dx,0.0,-dx), dir)).r, mn);
				sum += min(texture(drawing, center.xyz + cross(vec3(-dx,-dx,0.0), dir)).r, mn);

				sum += min(texture(drawing, center.xyz + cross(vec3(0.0,+dx,-dx), dir)).r, mn);
				sum += min(texture(drawing, center.xyz + cross(vec3(+dx,0.0,-dx), dir)).r, mn);
				sum += min(texture(drawing, center.xyz + cross(vec3(+dx,-dx,0.0), dir)).r, mn);
				
				sum += min(texture(drawing, center.xyz + cross(vec3(0.0,-dx,+dx), dir)).r, mn);
				sum += min(texture(drawing, center.xyz + cross(vec3(-dx,0.0,+dx), dir)).r, mn);
				sum += min(texture(drawing, center.xyz + cross(vec3(-dx,+dx,0.0), dir)).r, mn);
				float proportion = (sum / mn) / 18.0; //proportion of six neighbors is non-zero
				
				//a high proportion of hits means crevice
				//since the AO term adds shadows that darken most voxels, it will result in dark surfaces
				//the term brighten adds a little illumination to balance this
				// without brighten, only the most extreme ridges will not be darker
				const float brighten = 1.2;
				vec3 ao = draw.rgb * (1.0 - proportion) * brighten;
				draw.rgb = mix (draw.rgb, ao , renderDrawAmbientOcclusionX);
			}
			colorSample = draw;
			} // end else (discrete drawing path)
		}
		samplePos += deltaDir; //advance ray position
		if (colorSample.a >= 0.01) {
			if (overFirstHit.a > len)
				overFirstHit = samplePos;
			colorSample.a *= renderOverlayBlend;
			colorSample.a = 1.0-pow((1.0 - colorSample.a), opacityCorrection);
			colorSample.rgb *= colorSample.a;
			colAcc= (1.0 - colAcc.a) * colorSample + colAcc;
			overFarthest = samplePos.a;
			if ( colAcc.a > earlyTermination )
				break;
		}
	}
	//if (samplePos.a >= len) {
	if (colAcc.a <= 0.0) {
		if (isClip && (fColor.a == 0.0))
			fColor += clipPlaneColorX;
		return;
	}
	if (overFirstHit.a < firstHit.a)
		gl_FragDepth = frac2ndc(overFirstHit.xyz);
	float overMix = colAcc.a;
	float overlayDepth = 0.3;
	if (fColor.a <= 0.0)
		overMix = 1.0;
	else if (((overFarthest) > backNearest)) {
		float dx = (overFarthest - backNearest)/1.73;
		dx = fColor.a * pow(dx, overlayDepth);
		overMix *= 1.0 - dx;
	}
	fColor.rgb = mix(fColor.rgb, colAcc.rgb, overMix);
	fColor.a = max(fColor.a, colAcc.a);
}` // kRenderTail

// https://github.com/niivue/niivue/issues/679
export const fragRenderSliceShader =
    `#version 300 es
#line 215
#define MAX_CLIP_PLANES 6
precision highp int;
precision highp float;
uniform vec3 rayDir;
uniform vec3 texVox;
uniform int backgroundMasksOverlays;
uniform vec3 volScale;
uniform vec4 clipPlane;
uniform vec4 clipPlanes[MAX_CLIP_PLANES];
uniform highp sampler3D volume, overlay;
uniform highp sampler3D paqd;
uniform vec4 paqdUniforms;
uniform float overlays;
uniform float backOpacity;
uniform mat4 mvpMtx;
uniform mat4 matRAS;
uniform vec4 clipPlaneColor;
uniform float renderOverlayBlend;
uniform highp sampler3D drawing;
uniform highp sampler3D drawSmoothed;
uniform float smoothDrawing;
uniform highp sampler2D colormap;
uniform vec2 renderDrawAmbientOcclusionXY;
uniform bool isClipAllVolumes;
in vec3 vColor;
out vec4 fColor;
` +
    kRenderFunc +
    `
	void main() {
	vec3 start = vColor;
	gl_FragDepth = 1.0;
	vec3 backPosition = GetBackPosition(start);
	vec3 dir = normalize(backPosition - start);
	//clipVolumeStart(start, backPosition);
	float len = length(backPosition - start);
	float lenVox = length((texVox * start) - (texVox * backPosition));
	if ((lenVox < 0.5) || (len > 3.0)) { //length limit for parallel rays
		fColor = vec4(0.0,0.0,0.0,0.0);
		return;
	}
	float sliceSize = len / lenVox; //e.g. if ray length is 1.0 and traverses 50 voxels, each voxel is 0.02 in unit cube
	float stepSize = sliceSize; //quality: larger step is faster traversal, but fewer samples
	float opacityCorrection = stepSize/sliceSize;
	vec4 deltaDir = vec4(dir.xyz * stepSize, stepSize);
	vec4 samplePos = vec4(start.xyz, 0.0); //ray position
	vec4 colAcc = vec4(0.0,0.0,0.0,0.0);
	vec4 firstHit = vec4(0.0,0.0,0.0,2.0 * len);
	const float earlyTermination = 0.95;
	float backNearest = len; //assume no hit
	float dis = len;
	//check if axial plane is closest
	vec4 aClip = vec4(0.0, 0.0, 1.0, (1.0- clipPlane.z) - 0.5);
	float adis = (-aClip.a - dot(aClip.xyz, samplePos.xyz-0.5)) / dot(dir,aClip.xyz);
	if (adis > 0.0)
		dis = min(adis, dis);
	//check of coronal plane is closest
	vec4 cClip = vec4(0.0, 1.0, 0.0, (1.0- clipPlane.y) - 0.5);
	float cdis = (-cClip.a - dot(cClip.xyz, samplePos.xyz-0.5)) / dot(dir,cClip.xyz);
	if (cdis > 0.0)
		dis = min(cdis, dis);
	//check if coronal slice is closest
	vec4 sClip = vec4(1.0, 0.0, 0.0, (1.0- clipPlane.x) - 0.5);
	float sdis = (-sClip.a - dot(sClip.xyz, samplePos.xyz-0.5)) / dot(dir,sClip.xyz);
	if (sdis > 0.0)
		dis = min(sdis, dis);
	if ((dis > 0.0) && (dis < len)) {
		samplePos = vec4(samplePos.xyz+dir * dis, dis);
		colAcc = texture(volume, samplePos.xyz);
		colAcc.a = earlyTermination;
		firstHit = samplePos;
		backNearest = min(backNearest, samplePos.a);
	}
	//the following are only used by overlays
	vec4 clipPlaneColorX = clipPlaneColor;
	bool isColorPlaneInVolume = false;
	bool isClip = false;
	bool isClipCutaway = false;
	vec2 sampleRange = vec2(0.0, len);
	// vec4 clipPos = applyClip(dir, samplePos, len, isClip);
	float stepSizeFast = sliceSize * 1.9;
	vec4 deltaDirFast = vec4(dir.xyz * stepSizeFast, stepSizeFast);
	vec2 overlaySampleRange = vec2(0.0, len);
	bool overlayIsClipCutaway = false;
	if (samplePos.a < 0.0)
		vec4 samplePos = vec4(start.xyz, 0.0); //ray position
	float ran = fract(sin(gl_FragCoord.x * 12.9898 + gl_FragCoord.y * 78.233) * 43758.5453);
	samplePos += deltaDir * ran; //jitter ray
` +
    kRenderTail

export const fragRenderShader =
    `#version 300 es
#line 215
#define MAX_CLIP_PLANES 6
precision highp int;
precision highp float;
uniform vec3 rayDir;
uniform vec3 texVox;
uniform int backgroundMasksOverlays;
uniform vec3 volScale;
uniform vec4 clipPlane;
uniform vec4 clipPlanes[MAX_CLIP_PLANES];
uniform bool isClipCutaway;
uniform highp sampler3D volume, overlay;
uniform highp sampler3D paqd;
uniform vec4 paqdUniforms;
uniform float overlays;
uniform float backOpacity;
uniform mat4 mvpMtx;
uniform mat4 matRAS;
uniform vec4 clipPlaneColor;
uniform float renderOverlayBlend;
uniform highp sampler3D drawing;
uniform highp sampler3D drawSmoothed;
uniform float smoothDrawing;
uniform highp sampler2D colormap;
uniform vec2 renderDrawAmbientOcclusionXY;
uniform bool isClipAllVolumes;
in vec3 vColor;
out vec4 fColor;
` +
    kRenderFunc +
    kRenderInit +
    `while (samplePos.a <= len) {
		if (skipSample(samplePos.a, sampleRange) ^^ isClipCutaway) {
			samplePos += deltaDirFast;
			continue;
		}
		vec4 colorSample = texture(volume, samplePos.xyz);
		samplePos += deltaDir; //advance ray position
		if (colorSample.a >= 0.01) {
			if (firstHit.a > len)
				firstHit = samplePos;
			// backNearest = min(backNearest, samplePos.a);
			colorSample.a = 1.0-pow((1.0 - colorSample.a), opacityCorrection);
			colorSample.rgb *= colorSample.a;
			colAcc= (1.0 - colAcc.a) * colorSample + colAcc;
			if ( colAcc.a > earlyTermination )
				break;
		}
	}
	if (firstHit.a < len)
		backNearest = firstHit.a;
` +
    kRenderTail

export const gradientOpacityLutCount = 192

const kFragRenderGradientDecl = `#version 300 es
#line 215
#define MAX_CLIP_PLANES 6
precision highp int;
precision highp float;
uniform vec3 rayDir;
uniform vec3 texVox;
uniform int backgroundMasksOverlays;
uniform vec3 volScale;
uniform vec4 clipPlane;
uniform vec4 clipPlanes[MAX_CLIP_PLANES];
uniform bool isClipCutaway;
uniform highp sampler3D volume, overlay;
uniform highp sampler3D paqd;
uniform vec4 paqdUniforms;
uniform float overlays;
uniform float backOpacity;
uniform mat4 mvpMtx;
uniform mat4 normMtx;
uniform mat4 matRAS;
uniform vec4 clipPlaneColor;
uniform float renderOverlayBlend;
uniform highp sampler3D drawing, gradient;
uniform highp sampler3D drawSmoothed;
uniform float smoothDrawing;
uniform highp sampler2D colormap;
uniform highp sampler2D matCap;
uniform vec2 renderDrawAmbientOcclusionXY;
uniform float gradientAmount;
uniform float silhouettePower;
uniform float gradientOpacity[${gradientOpacityLutCount}];
uniform bool isClipAllVolumes;
in vec3 vColor;
out vec4 fColor;
`

export const fragRenderGradientShader =
    kFragRenderGradientDecl +
    kRenderFunc +
    kRenderInit +
    `
	float startPos = samplePos.a;
	float clipCloseThresh = 5.0 * deltaDir.a;
	float clipClose = sampleRange.x;
	if (isClipCutaway)
		clipClose = sampleRange.y;
	if (!isClip)
		clipClose = -1.0;
	float brighten = 2.0; //modulating makes average intensity darker 0.5 * 0.5 = 0.25
	//vec4 prevGrad = vec4(0.0);
	float silhouetteThreshold = 1.0 - silhouettePower;
	while (samplePos.a <= len) {
		if (skipSample(samplePos.a, sampleRange) ^^ isClipCutaway) {
			samplePos += deltaDirFast;
			continue;
		}
		vec4 colorSample = texture(volume, samplePos.xyz);
		if (colorSample.a >= 0.0) {
			vec4 grad = texture(gradient, samplePos.xyz);
			grad.rgb = grad.rgb*2.0 - 1.0;
			if (grad.a > 0.0)
				grad.rgb = normalize(grad.rgb);
			//if (grad.a < prevGrad.a)
			//	grad.rgb = prevGrad.rgb;
			//prevGrad = grad;
			vec3 n = mat3(normMtx) * grad.rgb;
			n.y = - n.y;
			vec4 mc = vec4(texture(matCap, n.xy * 0.5 + 0.5).rgb, 1.0) * brighten;
			mc = mix(vec4(1.0), mc, gradientAmount);
			if (abs(samplePos.a - clipClose) > clipCloseThresh)
				colorSample.rgb *= mc.rgb;
			if (firstHit.a > len)
				firstHit = samplePos;
			backNearest = min(backNearest, samplePos.a);
			colorSample.a = 1.0-pow((1.0 - colorSample.a), opacityCorrection);
			int gradIdx = int(grad.a * ${gradientOpacityLutCount}.0);
			colorSample.a *= gradientOpacity[gradIdx];
			float lightNormDot = dot(grad.rgb, rayDir);
			// n.b. "lightNormDor" is cosTheta, "silhouettePower" is Fresnel effect exponent
 			colorSample.a *= pow(1.0 - abs(lightNormDot), silhouettePower);
 			float viewAlign = abs(lightNormDot); // 0 = perpendicular, 1 = aligned
 			// linearly map silhouettePower (0..1) to a threshold range, e.g., [1.0, 0.0]
 			// Cull voxels that are too aligned with the view direction
 			if (viewAlign > silhouetteThreshold)
 				colorSample.a = 0.0;
			colorSample.rgb *= colorSample.a;
			colAcc= (1.0 - colAcc.a) * colorSample + colAcc;
			if ( colAcc.a > earlyTermination )
				break;
		}
		samplePos += deltaDir; //advance ray position
	}
` +
    kRenderTail

export const fragRenderGradientValuesShader =
    kFragRenderGradientDecl +
    kRenderFunc +
    kRenderInit +
    `
	float startPos = samplePos.a;
	//float clipClose = clipPos.a + 3.0 * deltaDir.a; //do not apply gradients near clip plane
	float brighten = 2.0; //modulating makes average intensity darker 0.5 * 0.5 = 0.25
	//vec4 prevGrad = vec4(0.0);
	while (samplePos.a <= len) {
		vec4 colorSample = texture(volume, samplePos.xyz);
		if (colorSample.a >= 0.0) {
			vec4 grad = texture(gradient, samplePos.xyz);
			grad.rgb = grad.rgb*2.0 - 1.0;
			if (grad.a > 0.0)
				grad.rgb = normalize(grad.rgb);
			colorSample.rgb = abs(grad.rgb);
			if (firstHit.a > len)
				firstHit = samplePos;
			backNearest = min(backNearest, samplePos.a);
			colorSample.a = 1.0-pow((1.0 - colorSample.a), opacityCorrection);
			colorSample.rgb *= colorSample.a;
			colAcc= (1.0 - colAcc.a) * colorSample + colAcc;
			if ( colAcc.a > earlyTermination )
				break;
		}
		samplePos += deltaDir; //advance ray position
	}
` +
    kRenderTail

export const vertSliceMMShader = `#version 300 es
#line 392
layout(location=0) in vec3 pos;
uniform int axCorSag;
uniform mat4 mvpMtx;
uniform mat4 frac2mm;
uniform float slice;
out vec3 texPos;
void main(void) {
	texPos = vec3(pos.x, pos.y, slice);
	if (axCorSag > 1)
		texPos = vec3(slice, pos.x, pos.y);
	else if (axCorSag > 0)
		texPos = vec3(pos.x, slice, pos.y);
	vec4 mm = frac2mm * vec4(texPos, 1.0);
	gl_Position = mvpMtx * mm;
}`

export const kFragSliceHead =
    `#version 300 es
#line 411
precision highp int;
precision highp float;
uniform highp sampler3D volume, overlay;
uniform highp sampler3D paqd;
uniform vec4 paqdUniforms;
uniform int backgroundMasksOverlays;
uniform float overlayOutlineWidth;
uniform float overlayAlphaShader;
uniform int axCorSag;
uniform float overlays;
uniform float opacity;
uniform float drawOpacity;
uniform float drawRimOpacity;
uniform bool isAlphaClipDark;
uniform highp sampler3D drawing;
uniform highp sampler2D colormap;
in vec3 texPos;
out vec4 color;
` +
    kDrawFunc +
    `
vec4 blendRGBA(vec4 foreground, vec4 background) {
  float alphaOut = foreground.a + background.a * (1.0 - foreground.a);
  vec3 colorOut = (foreground.rgb * foreground.a + background.rgb * background.a * (1.0 - foreground.a)) / alphaOut;
  return vec4(colorOut, alphaOut);
}
float paqdEaseAlpha(float alpha) {
  // t are alpha transitions
  // <t0 -> y0
  // t0..t1  -> mix between y0..y1
  // t1..t2 -> mix between y1..y2
  // >t2 -> y2
  float t0 = paqdUniforms[0]; // 0.3;
  float t1 = 0.5 * (paqdUniforms[0] + paqdUniforms[1]); // 0.4;
  float t2 = paqdUniforms[1]; // 0.9;
  float y0 = 0.0;
  float y1 = abs(paqdUniforms[2]); // 1.0;
  float y2 = abs(paqdUniforms[3]); //0.25;
  if (alpha <= t0) {
    return y0;
  } else if (alpha <= t1) {
    return mix(y0, y1, (alpha - t0) / (t1 - t0)); // LERP 0.0 → 1.0
  } else if (alpha <= t2) {
    return mix(y1, y2, (alpha - t1) / (t2 - t1)); // LERP 1.0 → 0.2
  } else {
    return y2;
  }
}

void main() {
	//color = vec4(1.0, 0.0, 1.0, 1.0);return;
	vec4 background = texture(volume, texPos);
	color = vec4(background.rgb, opacity);
	if ((isAlphaClipDark) && (background.a == 0.0)) color.a = 0.0; //FSLeyes clipping range
	vec4 ocolor = vec4(0.0);
	float overlayAlpha = overlayAlphaShader;
	if (overlays > 0.0) {
		ocolor = texture(overlay, texPos);
		//dFdx for "boxing" issue 435 has aliasing on some implementations (coarse vs fine)
		//however, this only identifies 50% of the edges due to aliasing effects
		// http://www.aclockworkberry.com/shader-derivative-functions/
		// https://bgolus.medium.com/distinctive-derivative-differences-cce38d36797b
		//if ((ocolor.a >= 1.0) && ((dFdx(ocolor.a) != 0.0) || (dFdy(ocolor.a) != 0.0)  ))
		//	ocolor.rbg = vec3(0.0, 0.0, 0.0);
		bool isOutlineBelowNotAboveThreshold = true;
		if (isOutlineBelowNotAboveThreshold) {
			if ((overlayOutlineWidth > 0.0) && (ocolor.a < 1.0)) { //check voxel neighbors for edge
				vec3 vx = (overlayOutlineWidth ) / vec3(textureSize(overlay, 0));
				//6 voxel neighbors that share a face
				vec3 vxR = vec3(texPos.x+vx.x, texPos.y, texPos.z);
				vec3 vxL = vec3(texPos.x-vx.x, texPos.y, texPos.z);
				vec3 vxA = vec3(texPos.x, texPos.y+vx.y, texPos.z);
				vec3 vxP = vec3(texPos.x, texPos.y-vx.y, texPos.z);
				vec3 vxS = vec3(texPos.x, texPos.y, texPos.z+vx.z);
				vec3 vxI = vec3(texPos.x, texPos.y, texPos.z-vx.z);
				float a = 0.0;
				if (axCorSag != 2) {
					a = max(a, texture(overlay, vxR).a);
					a = max(a, texture(overlay, vxL).a);
				}
				if (axCorSag != 1) {
					a = max(a, texture(overlay, vxA).a);
					a = max(a, texture(overlay, vxP).a);
				}
				if (axCorSag != 0) {
					a = max(a, texture(overlay, vxS).a);
					a = max(a, texture(overlay, vxI).a);
				}
				bool isCheckCorners = true;
				if (isCheckCorners) {
					//12 voxel neighbors that share an edge
					vec3 vxRA = vec3(texPos.x+vx.x, texPos.y+vx.y, texPos.z);
					vec3 vxLA = vec3(texPos.x-vx.x, texPos.y+vx.y, texPos.z);
					vec3 vxRP = vec3(texPos.x+vx.x, texPos.y-vx.y, texPos.z);
					vec3 vxLP = vec3(texPos.x-vx.x, texPos.y-vx.y, texPos.z);
					vec3 vxRS = vec3(texPos.x+vx.x, texPos.y, texPos.z+vx.z);
					vec3 vxLS = vec3(texPos.x-vx.x, texPos.y, texPos.z+vx.z);
					vec3 vxRI = vec3(texPos.x+vx.x, texPos.y, texPos.z-vx.z);
					vec3 vxLI = vec3(texPos.x-vx.x, texPos.y, texPos.z-vx.z);
					vec3 vxAS = vec3(texPos.x, texPos.y+vx.y, texPos.z+vx.z);
					vec3 vxPS = vec3(texPos.x, texPos.y-vx.y, texPos.z+vx.z);
					vec3 vxAI = vec3(texPos.x, texPos.y+vx.y, texPos.z-vx.z);
					vec3 vxPI = vec3(texPos.x, texPos.y-vx.y, texPos.z-vx.z);

					if (axCorSag == 0) { //axial corners
						a = max(a, texture(overlay, vxRA).a);
						a = max(a, texture(overlay, vxLA).a);
						a = max(a, texture(overlay, vxRP).a);
						a = max(a, texture(overlay, vxLP).a);
					}
					if (axCorSag == 1) { //coronal corners
						a = max(a, texture(overlay, vxRS).a);
						a = max(a, texture(overlay, vxLS).a);
						a = max(a, texture(overlay, vxRI).a);
						a = max(a, texture(overlay, vxLI).a);
					}
					if (axCorSag == 2) { //sagittal corners
						a = max(a, texture(overlay, vxAS).a);
						a = max(a, texture(overlay, vxPS).a);
						a = max(a, texture(overlay, vxAI).a);
						a = max(a, texture(overlay, vxPI).a);
					}
				}
				if (a >= 1.0) {
					ocolor = vec4(0.0, 0.0, 0.0, 1.0);
					overlayAlpha = 1.0;
				}
			}

		} else {
			if ((overlayOutlineWidth > 0.0) && (ocolor.a >= 1.0)) { //check voxel neighbors for edge
				vec3 vx = (overlayOutlineWidth ) / vec3(textureSize(overlay, 0));
				vec3 vxR = vec3(texPos.x+vx.x, texPos.y, texPos.z);
				vec3 vxL = vec3(texPos.x-vx.x, texPos.y, texPos.z);
				vec3 vxA = vec3(texPos.x, texPos.y+vx.y, texPos.z);
				vec3 vxP = vec3(texPos.x, texPos.y-vx.y, texPos.z);
				vec3 vxS = vec3(texPos.x, texPos.y, texPos.z+vx.z);
				vec3 vxI = vec3(texPos.x, texPos.y, texPos.z-vx.z);
				float a = 1.0;
				if (axCorSag != 2) {
					a = min(a, texture(overlay, vxR).a);
					a = min(a, texture(overlay, vxL).a);
				}
				if (axCorSag != 1) {
					a = min(a, texture(overlay, vxA).a);
					a = min(a, texture(overlay, vxP).a);
				}
				if (axCorSag != 0) {
					a = min(a, texture(overlay, vxS).a);
					a = min(a, texture(overlay, vxI).a);
				}
				if (a < 1.0) {
					ocolor = vec4(0.0, 0.0, 0.0, 1.0);
					overlayAlpha = 1.0;
				}
			}
		} //outline above threshold
	}

`

export const fragSlice2DShader =
    `#version 300 es
#line 411
precision highp int;
precision highp float;
uniform highp sampler2D volume, overlay;
uniform int backgroundMasksOverlays;
uniform float overlayOutlineWidth;
uniform float overlayAlphaShader;
uniform int axCorSag;
uniform float overlays;
uniform float opacity;
uniform float drawOpacity;
uniform bool isAlphaClipDark;
uniform highp sampler2D drawing;
uniform highp sampler2D colormap;
in vec3 texPos;
out vec4 color;` +
    kDrawFunc +
    `void main() {
	//color = vec4(1.0, 0.0, 1.0, 1.0);return;
	vec4 background = texture(volume, texPos.xy);
	color = vec4(background.rgb, opacity);
	if ((isAlphaClipDark) && (background.a == 0.0)) color.a = 0.0; //FSLeyes clipping range
	vec4 dcolor = drawColor(texture(drawing, texPos.xy).r, drawOpacity);
	if (dcolor.a > 0.0) {
		color.rgb = mix(color.rgb, dcolor.rgb, dcolor.a);
		color.a = max(drawOpacity, color.a);
	}
}`

export const kFragSliceTail = `	ocolor.a *= overlayAlpha;
	float drawV = texture(drawing, texPos).r;
	vec4 dcolor = drawColor(drawV, drawOpacity);
	if (dcolor.a > 0.0) {
		if (drawRimOpacity >= 0.0) {
			vec3 vx = 1.0 / vec3(textureSize(drawing, 0));
			//6 voxel neighbors that share a face
			vec3 offsetX = dFdx(texPos); // left-right spacing
			vec3 offsetY = dFdy(texPos); // up-down spacing
			float L = texture(drawing, texPos - offsetX).r;
			float R = texture(drawing, texPos + offsetX).r;
			float T = texture(drawing, texPos - offsetY).r;
			float B = texture(drawing, texPos + offsetY).r;
			if (L != drawV || R != drawV || T != drawV || B != drawV)
				dcolor.a = drawRimOpacity;
		}
		color.rgb = mix(color.rgb, dcolor.rgb, dcolor.a);
		color.a = max(drawOpacity, color.a);
	}
	vec4 pcolor = texture(paqd, texPos);
	if (pcolor.a > 0.0) {
		pcolor.a = paqdEaseAlpha(pcolor.a);
		if (pcolor.a > 0.0) {
			if (paqdUniforms[3] < 0.0)
				ocolor = blendRGBA(pcolor, ocolor);
			else
				ocolor = blendRGBA(ocolor, pcolor);
		}
	}
	if ((backgroundMasksOverlays > 0) && (background.a == 0.0))
		return;
	float a = color.a + ocolor.a * (1.0 - color.a); // premultiplied alpha
	if (a == 0.0) return;
	color.rgb = mix(color.rgb, ocolor.rgb, ocolor.a / a);
	color.a = a;
}`

export const fragSliceMMShader = kFragSliceHead + kFragSliceTail

export const fragSliceV1Shader =
    kFragSliceHead +
    `	if (ocolor.a > 0.0) {
		//https://gamedev.stackexchange.com/questions/102889/is-it-possible-to-convert-vec4-to-int-in-glsl-using-opengl-es
		uint alpha = uint(ocolor.a * 255.0);
		vec3 xyzFlip = vec3(float((uint(1) & alpha) > uint(0)), float((uint(2) & alpha) > uint(0)), float((uint(4) & alpha) > uint(0)));
		//convert from 0 and 1 to -1 and 1
		xyzFlip = (xyzFlip * 2.0) - 1.0;
		//https://math.stackexchange.com/questions/1905533/find-perpendicular-distance-from-point-to-line-in-3d
		//v1 principle direction of tensor for this voxel
		vec3 v1 = ocolor.rgb;
		//flips encode polarity to convert from 0..1 to -1..1 (27 bits vs 24 bit precision)
		v1 = normalize( v1 * xyzFlip);
		vec3 vxl = fract(texPos * vec3(textureSize(volume, 0))) - 0.5;
		//vxl coordinates now -0.5..+0.5 so 0,0,0 is origin
		vxl.x = -vxl.x;
		float t = dot(vxl,v1);
		vec3 P = t * v1;
		float dx = length(P-vxl);
		ocolor.a = 1.0 - smoothstep(0.2,0.25, dx);
		//if modulation was applied, use that to scale alpha not color:
		ocolor.a *= length(ocolor.rgb);
		ocolor.rgb = normalize(ocolor.rgb);
		//compute distance one half voxel closer to viewer:
		float pan = 0.5;
		if (axCorSag == 0)
			vxl.z -= pan;
		if (axCorSag == 1)
			vxl.y -= pan;
		if (axCorSag == 2)
			vxl.x += pan;
		t = dot(vxl,v1);
		P = t * v1;
		float dx2 = length(P-vxl);
		ocolor.rgb += (dx2-dx-(0.5 * pan)) * 1.0;
	}
` +
    kFragSliceTail

export const fragRectShader = `#version 300 es
#line 480
precision highp int;
precision highp float;
uniform vec4 lineColor;
out vec4 color;
void main() {
	color = lineColor;
}`

export const fragRectOutlineShader = `#version 300 es
#line 723
precision highp int;
precision highp float;

uniform vec4 lineColor;
uniform vec4 leftTopWidthHeight;
uniform float thickness; // line thickness in pixels
uniform vec2 canvasWidthHeight;

out vec4 color;

void main() {
    // fragment position in screen coordinates
    vec2 fragCoord = gl_FragCoord.xy;

    // canvas height
    float canvasHeight = canvasWidthHeight.y;

    // 'top' and 'bottom' to match gl_FragCoord.y coordinate system
    float top = canvasHeight - leftTopWidthHeight.y;
    float bottom = top - leftTopWidthHeight.w;

    // left and right edges
    float left = leftTopWidthHeight.x;
    float right = left + leftTopWidthHeight.z;

    bool withinLeft = fragCoord.x >= left && fragCoord.x <= left + thickness;
    bool withinRight = fragCoord.x <= right && fragCoord.x >= right - thickness;
    bool withinTop = fragCoord.y <= top && fragCoord.y >= top - thickness;
    bool withinBottom = fragCoord.y >= bottom && fragCoord.y <= bottom + thickness;

    bool isOutline = withinLeft || withinRight || withinTop || withinBottom;

    if (isOutline) {
        color = lineColor;
    } else {
        discard; 
    }
}`

export const vertColorbarShader = `#version 300 es
#line 490
layout(location=0) in vec3 pos;
uniform vec2 canvasWidthHeight;
uniform vec4 leftTopWidthHeight;
out vec2 vColor;
void main(void) {
	//convert pixel x,y space 1..canvasWidth,1..canvasHeight to WebGL 1..-1,-1..1
	vec2 frac;
	frac.x = (leftTopWidthHeight.x + (pos.x * leftTopWidthHeight.z)) / canvasWidthHeight.x; //0..1
	frac.y = 1.0 - ((leftTopWidthHeight.y + ((1.0 - pos.y) * leftTopWidthHeight.w)) / canvasWidthHeight.y); //1..0
	frac = (frac * 2.0) - 1.0;
	gl_Position = vec4(frac, 0.0, 1.0);
	vColor = pos.xy;
}`

export const fragColorbarShader = `#version 300 es
#line 506
precision highp int;
precision highp float;
uniform highp sampler2D colormap;
uniform float layer;
in vec2 vColor;
out vec4 color;
void main() {
	float nlayer = float(textureSize(colormap, 0).y);
	float fmap = (0.5 + layer) / nlayer;
	color = vec4(texture(colormap, vec2(vColor.x, fmap)).rgb, 1.0);
}`

export const vertRectShader = `#version 300 es
#line 520
layout(location=0) in vec3 pos;
uniform vec2 canvasWidthHeight;
uniform vec4 leftTopWidthHeight;
void main(void) {
	//convert pixel x,y space 1..canvasWidth,1..canvasHeight to WebGL 1..-1,-1..1
	vec2 frac;
	frac.x = (leftTopWidthHeight.x + (pos.x * leftTopWidthHeight.z)) / canvasWidthHeight.x; //0..1
	frac.y = 1.0 - ((leftTopWidthHeight.y + ((1.0 - pos.y) * leftTopWidthHeight.w)) / canvasWidthHeight.y); //1..0
	frac = (frac * 2.0) - 1.0;
	gl_Position = vec4(frac, 0.0, 1.0);
}`

export const vertLineShader = `#version 300 es
#line 534
layout(location=0) in vec3 pos;
uniform vec2 canvasWidthHeight;
uniform float thickness;
uniform vec4 startXYendXY;
void main(void) {
	vec2 posXY = mix(startXYendXY.xy, startXYendXY.zw, pos.x);
	vec2 dir = normalize(startXYendXY.xy - startXYendXY.zw);
	posXY += vec2(-dir.y, dir.x) * thickness * (pos.y - 0.5);
	posXY.x = (posXY.x) / canvasWidthHeight.x; //0..1
	posXY.y = 1.0 - (posXY.y / canvasWidthHeight.y); //1..0
	gl_Position = vec4((posXY * 2.0) - 1.0, 0.0, 1.0);
}`

export const vertLine3DShader = `#version 300 es
#line 534
layout(location=0) in vec3 pos;
uniform vec2 canvasWidthHeight;
uniform float thickness;
uniform vec2 startXY;
uniform vec3 endXYZ; // transformed XYZ point
void main(void) {	
	vec2 posXY = mix(startXY.xy, endXYZ.xy, pos.x);
	vec2 startDiff = endXYZ.xy - startXY.xy;
	float startDistance = length(startDiff);
	vec2 diff = endXYZ.xy - posXY;
	float currentDistance = length(diff);
	vec2 dir = normalize(startXY.xy - endXYZ.xy);
	posXY += vec2(-dir.y, dir.x) * thickness * (pos.y - 0.5);
	posXY.x = (posXY.x) / canvasWidthHeight.x; //0..1
	posXY.y = 1.0 - (posXY.y / canvasWidthHeight.y); //1..0	
	float z = endXYZ.z * ( 1.0 - abs(currentDistance/startDistance)); 
	gl_Position = vec4((posXY * 2.0) - 1.0, z, 1.0);
}`

export const vertBmpShader = `#version 300 es
#line 549
layout(location=0) in vec3 pos;
uniform vec2 canvasWidthHeight;
uniform vec4 leftTopWidthHeight;
out vec2 vUV;
void main(void) {
	//convert pixel x,y space 1..canvasWidth,1..canvasHeight to WebGL 1..-1,-1..1
	vec2 frac;
	frac.x = (leftTopWidthHeight.x + (pos.x * leftTopWidthHeight.z)) / canvasWidthHeight.x; //0..1
	frac.y = 1.0 - ((leftTopWidthHeight.y + ((1.0 - pos.y) * leftTopWidthHeight.w)) / canvasWidthHeight.y); //1..0
	frac = (frac * 2.0) - 1.0;
	gl_Position = vec4(frac, 0.0, 1.0);
	vUV = vec2(pos.x, 1.0 - pos.y);
}`

export const fragBmpShader = `#version 300 es
#line 565
precision highp int;
precision highp float;
uniform highp sampler2D bmpTexture;
in vec2 vUV;
out vec4 color;
void main() {
	color = texture(bmpTexture, vUV);
}`

export const vertFontShader = `#version 300 es
#line 576
layout(location=0) in vec3 pos;
uniform vec2 canvasWidthHeight;
uniform vec4 leftTopWidthHeight;
uniform vec4 uvLeftTopWidthHeight;
out vec2 vUV;
void main(void) {
	//convert pixel x,y space 1..canvasWidth,1..canvasHeight to WebGL 1..-1,-1..1
	vec2 frac;
	frac.x = (leftTopWidthHeight.x + (pos.x * leftTopWidthHeight.z)) / canvasWidthHeight.x; //0..1
	frac.y = 1.0 - ((leftTopWidthHeight.y + ((1.0 - pos.y) * leftTopWidthHeight.w)) / canvasWidthHeight.y); //1..0
	frac = (frac * 2.0) - 1.0;
	gl_Position = vec4(frac, 0.0, 1.0);
	vUV = vec2(uvLeftTopWidthHeight.x + (pos.x * uvLeftTopWidthHeight.z), uvLeftTopWidthHeight.y  + ((1.0 - pos.y) * uvLeftTopWidthHeight.w) );
}`

export const fragFontShader = `#version 300 es
#line 593
precision highp int;
precision highp float;
uniform highp sampler2D fontTexture;
uniform vec4 fontColor;
uniform float screenPxRange;
in vec2 vUV;
out vec4 color;
float median(float r, float g, float b) {
	return max(min(r, g), min(max(r, g), b));
}
void main() {
	vec3 msd = texture(fontTexture, vUV).rgb;
	float sd = median(msd.r, msd.g, msd.b);
	float screenPxDistance = screenPxRange*(sd - 0.5);
	float opacity = clamp(screenPxDistance + 0.5, 0.0, 1.0);
	color = vec4(fontColor.rgb , fontColor.a * opacity);
}`

export const vertCircleShader = `#version 300 es
layout(location=0) in vec3 pos;
uniform vec2 canvasWidthHeight;
uniform vec4 leftTopWidthHeight;
uniform vec4 uvLeftTopWidthHeight;
out vec2 vUV;
void main(void) {
	//convert pixel x,y space 1..canvasWidth,1..canvasHeight to WebGL 1..-1,-1..1
	vec2 frac;
	frac.x = (leftTopWidthHeight.x + (pos.x * leftTopWidthHeight.z)) / canvasWidthHeight.x; //0..1
	frac.y = 1.0 - ((leftTopWidthHeight.y + ((1.0 - pos.y) * leftTopWidthHeight.w)) / canvasWidthHeight.y); //1..0
	frac = (frac * 2.0) - 1.0;
	gl_Position = vec4(frac, 0.0, 1.0);
	vUV = pos.xy;
}`

export const fragCircleShader = `#version 300 es
precision highp int;
precision highp float;
uniform vec4 circleColor;
uniform float fillPercent;
in vec2 vUV;
out vec4 color;
void main() {
	/* Check if the pixel is inside the circle
		 and color it with a gradient. Otherwise, color it 
		 transparent   */
	float distance = length(vUV-vec2(0.5,0.5));
	if ( distance < 0.5 && distance >= (1.0 - fillPercent) / 2.0){
			color = vec4(circleColor.r,circleColor.g,circleColor.b,circleColor.a) ;			
	}else{
			color = vec4(0.0,0.0,0.0,0.0);
	}
}
`

export const vertOrientShader = `#version 300 es
#line 613
precision highp int;
precision highp float;
in vec3 vPos;
out vec2 TexCoord;
void main() {
	TexCoord = vPos.xy;
	gl_Position = vec4( (vPos.xy-vec2(0.5,0.5)) * 2.0, 0.0, 1.0);
}`

export const fragOrientShaderU = `#version 300 es
uniform highp usampler3D intensityVol;
`

export const fragOrientShaderI = `#version 300 es
uniform highp isampler3D intensityVol;
`

export const fragOrientShaderF = `#version 300 es
uniform highp sampler3D intensityVol;
`

export const fragOrientShaderAtlas = `#line 1042
precision highp int;
precision highp float;
in vec2 TexCoord;
out vec4 FragColor;
uniform bool isAdditiveBlend;
uniform float coordZ;
uniform float layer;
uniform highp sampler2D colormap;
uniform lowp sampler3D blend3D;
uniform float opacity;
uniform uint activeIndex;
uniform vec4 xyzaFrac;
uniform mat4 mtx;
float textureWidth;
float nlayer;
float layerY;

vec4 scalar2color(uint idx) {
	float fx = (float(idx) + 0.5) / textureWidth;
	vec4 clr = texture(colormap, vec2(fx, layerY)).rgba;
	if (clr.a > 0.0)
		clr.a = 1.0;
	clr.a *= opacity;
	return clr;
}
void main(void) {
	vec4 vx = vec4(TexCoord.x, TexCoord.y, coordZ, 1.0) * mtx;
	uint idx = uint(texture(intensityVol, vx.xyz).r);
	if (idx == uint(0)) {
		if (layer < 1.0) {
			FragColor = vec4(0.0, 0.0, 0.0, 0.0);
			return;
		}
		FragColor = texture(blend3D, vec3(TexCoord.xy, coordZ));
		return;
	}
	textureWidth = float(textureSize(colormap, 0).x);
	nlayer = float(textureSize(colormap, 0).y);
	layerY = ((2.0 * layer) + 1.5) / nlayer;
	//idx = ((idx - uint(1)) % uint(100))+uint(1);
	FragColor = scalar2color(idx);
	bool isBorder = false;
	vx = vec4(TexCoord.x+xyzaFrac.x, TexCoord.y, coordZ, 1.0) * mtx;
	uint R = uint(texture(intensityVol, vx.xyz).r);
	vx = vec4(TexCoord.x-xyzaFrac.x, TexCoord.y, coordZ, 1.0) * mtx;
	uint L = uint(texture(intensityVol, vx.xyz).r);
	vx = vec4(TexCoord.x, TexCoord.y+xyzaFrac.y, coordZ, 1.0) * mtx;
	uint A = uint(texture(intensityVol, vx.xyz).r);
	vx = vec4(TexCoord.x, TexCoord.y-xyzaFrac.y, coordZ, 1.0) * mtx;
	uint P = uint(texture(intensityVol, vx.xyz).r);
	vx = vec4(TexCoord.x, TexCoord.y, coordZ+xyzaFrac.z, 1.0) * mtx;
	uint S = uint(texture(intensityVol, vx.xyz).r);
	vx = vec4(TexCoord.x, TexCoord.y, coordZ-xyzaFrac.z, 1.0) * mtx;
	uint I = uint(texture(intensityVol, vx.xyz).r);
	vec4 centerColor = FragColor;
	FragColor.a += scalar2color(R).a;
	FragColor.a += scalar2color(L).a;
	FragColor.a += scalar2color(A).a;
	FragColor.a += scalar2color(P).a;
	FragColor.a += scalar2color(S).a;
	FragColor.a += scalar2color(I).a;
	FragColor.a /= 7.0;
	if ((!isBorder) &&(idx == activeIndex)) {
		if (centerColor.a > 0.5)
			FragColor.a *= 0.4;
		else
			FragColor.a =0.8;
	}
	if (xyzaFrac.a != 0.0) { //outline
		if ((idx != R) || (idx != L) || (idx != A) || (idx != P) || (idx != S) || (idx != I)) {
			isBorder = true;
			if (xyzaFrac.a > 0.0)
				FragColor.a = xyzaFrac.a;
			else
				FragColor = vec4(0.0, 0.0, 0.0, 1.0);
		}
	}
	if (layer < 1.0) return;
		vec4 prevColor = texture(blend3D, vec3(TexCoord.xy, coordZ));
		// https://en.wikipedia.org/wiki/Alpha_compositing
		float aout = FragColor.a + (1.0 - FragColor.a) * prevColor.a;
		if (aout <= 0.0) return;
		if (isAdditiveBlend)
			FragColor.rgb = ((FragColor.rgb * FragColor.a) + (prevColor.rgb * prevColor.a)) / aout;
		else
			FragColor.rgb = ((FragColor.rgb * FragColor.a) + (prevColor.rgb * prevColor.a * (1.0 - FragColor.a))) / aout;
		FragColor.a = aout;
}`

export const fragOrientShader = `#line 691
precision highp int;
precision highp float;
in vec2 TexCoord;
out vec4 FragColor;
uniform float coordZ;
uniform float layer;
uniform float scl_slope;
uniform float scl_inter;
uniform float cal_max;
uniform float cal_min;
uniform float cal_maxNeg;
uniform float cal_minNeg;
uniform bool isAlphaThreshold;
uniform bool isColorbarFromZero;
uniform bool isAdditiveBlend;
uniform highp sampler2D colormap;
uniform lowp sampler3D blend3D;
uniform int modulation;
uniform highp sampler3D modulationVol;
uniform float opacity;
uniform mat4 mtx;
void main(void) {
	vec4 vx = vec4(TexCoord.xy, coordZ, 1.0) * mtx;
	if ((vx.x < 0.0) || (vx.x > 1.0) || (vx.y < 0.0) || (vx.y > 1.0) || (vx.z < 0.0) || (vx.z > 1.0)) {
		//set transparent if out of range
		//https://webglfundamentals.org/webgl/webgl-3d-textures-repeat-clamp.html
		FragColor = texture(blend3D, vec3(TexCoord.xy, coordZ));
		return;
	}
	float f = (scl_slope * float(texture(intensityVol, vx.xyz).r)) + scl_inter;
	float mn = cal_min;
	float mx = cal_max;
	if ((isAlphaThreshold) || (isColorbarFromZero))
		mn = 0.0;
	float r = max(0.00001, abs(mx - mn));
	mn = min(mn, mx);
	float txl = mix(0.0, 1.0, (f - mn) / r);
	if (f > mn) { //issue1139: survives threshold, so round up to opaque voxel
		txl = max(txl, 2.0/256.0);
	}
	//https://stackoverflow.com/questions/5879403/opengl-texture-coordinates-in-pixel-space
	float nlayer = float(textureSize(colormap, 0).y);
	//each volume has two color maps:
	// (layer*2) = negative and (layer * 2) + 1 = positive
	float y = ((2.0 * layer) + 1.5)/nlayer;
	FragColor = texture(colormap, vec2(txl, y)).rgba;
	//negative colors
	mn = cal_minNeg;
	mx = cal_maxNeg;
	if ((isAlphaThreshold) || (isColorbarFromZero))
		mx = 0.0;
	//if ((!isnan(cal_minNeg)) && ( f < mx)) {
	if ((cal_minNeg < cal_maxNeg) && ( f < mx)) {
		r = max(0.00001, abs(mx - mn));
		mn = min(mn, mx);
		txl = 1.0 - mix(0.0, 1.0, (f - mn) / r);
		//issue1139: survives threshold, so round up to opaque voxel
		txl = max(txl, 2.0/256.0);
		y = ((2.0 * layer) + 0.5)/nlayer;
		FragColor = texture(colormap, vec2(txl, y));
	}
	if (layer > 0.7)
		FragColor.a = step(0.00001, FragColor.a);
	//if (modulation > 10)
	//	FragColor.a *= texture(modulationVol, vx.xyz).r;
	//	FragColor.rgb *= texture(modulationVol, vx.xyz).r;
	if (isAlphaThreshold) {
		if ((cal_minNeg != cal_maxNeg) && ( f < 0.0) && (f > cal_maxNeg))
			FragColor.a = pow(-f / -cal_maxNeg, 2.0);
		else if ((f > 0.0) && (c