@thewtex/vtk.js-esm/Rendering/OpenGL/glsl/vtkVolumeFS.glsl.js

Visualization Toolkit for the Web

var vtkVolumeFS = "//VTK::System::Dec\n\n/*=========================================================================\n\n  Program:   Visualization Toolkit\n  Module:    vtkVolumeFS.glsl\n\n  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen\n  All rights reserved.\n  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.\n\n     This software is distributed WITHOUT ANY WARRANTY; without even\n     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR\n     PURPOSE.  See the above copyright notice for more information.\n\n=========================================================================*/\n// Template for the volume mappers fragment shader\n\n// the output of this shader\n//VTK::Output::Dec\n\nvarying vec3 vertexVCVSOutput;\n\n// first declare the settings from the mapper\n// that impact the code paths in here\n\n// always set vtkNumComponents 1,2,3,4\n//VTK::NumComponents\n\n// possibly define vtkUseTriliear\n//VTK::TrilinearOn\n\n// possibly define vtkIndependentComponents\n//VTK::IndependentComponentsOn\n\n// possibly define any \"proportional\" components\n//VTK::vtkProportionalComponents\n\n// Define the blend mode to use\n#define vtkBlendMode //VTK::BlendMode\n\n// Possibly define vtkImageLabelOutlineOn\n//VTK::ImageLabelOutlineOn\n\n#ifdef vtkImageLabelOutlineOn\nuniform int outlineThickness;\nuniform float vpWidth;\nuniform float vpHeight;\nuniform mat4 PCWCMatrix;\nuniform mat4 vWCtoIDX;\n#endif\n\n// define vtkLightComplexity\n//VTK::LightComplexity\n#if vtkLightComplexity > 0\nuniform float vSpecularPower;\nuniform float vAmbient;\nuniform float vDiffuse;\nuniform float vSpecular;\n//VTK::Light::Dec\n#endif\n\n// possibly define vtkGradientOpacityOn\n//VTK::GradientOpacityOn\n#ifdef vtkGradientOpacityOn\nuniform float goscale0;\nuniform float goshift0;\nuniform float gomin0;\nuniform float gomax0;\n#if defined(vtkIndependentComponentsOn) && (vtkNumComponents > 1)\nuniform float goscale1;\nuniform float goshift1;\nuniform float gomin1;\nuniform float gomax1;\n#if vtkNumComponents >= 3\nuniform float goscale2;\nuniform float goshift2;\nuniform float gomin2;\nuniform float gomax2;\n#endif\n#if vtkNumComponents >= 4\nuniform float goscale3;\nuniform float goshift3;\nuniform float gomin3;\nuniform float gomax3;\n#endif\n#endif\n#endif\n\n// if you want to see the raw tiled\n// data in webgl1 uncomment the following line\n// #define debugtile\n\n// camera values\nuniform float camThick;\nuniform float camNear;\nuniform float camFar;\nuniform int cameraParallel;\n\n// values describing the volume geometry\nuniform vec3 vOriginVC;\nuniform vec3 vSpacing;\nuniform ivec3 volumeDimensions; // 3d texture dimensions\nuniform vec3 vPlaneNormal0;\nuniform float vPlaneDistance0;\nuniform vec3 vPlaneNormal1;\nuniform float vPlaneDistance1;\nuniform vec3 vPlaneNormal2;\nuniform float vPlaneDistance2;\nuniform vec3 vPlaneNormal3;\nuniform float vPlaneDistance3;\nuniform vec3 vPlaneNormal4;\nuniform float vPlaneDistance4;\nuniform vec3 vPlaneNormal5;\nuniform float vPlaneDistance5;\n\n//VTK::ClipPlane::Dec\n\n// opacity and color textures\nuniform sampler2D otexture;\nuniform float oshift0;\nuniform float oscale0;\nuniform sampler2D ctexture;\nuniform float cshift0;\nuniform float cscale0;\n\n// jitter texture\nuniform sampler2D jtexture;\n\n// some 3D texture values\nuniform float sampleDistance;\nuniform vec3 vVCToIJK;\n\n// the heights defined below are the locations\n// for the up to four components of the tfuns\n// the tfuns have a height of 2XnumComps pixels so the\n// values are computed to hit the middle of the two rows\n// for that component\n#ifdef vtkIndependentComponentsOn\n#if vtkNumComponents == 2\nuniform float mix0;\nuniform float mix1;\n#define height0 0.25\n#define height1 0.75\n#endif\n#if vtkNumComponents == 3\nuniform float mix0;\nuniform float mix1;\nuniform float mix2;\n#define height0 0.17\n#define height1 0.5\n#define height2 0.83\n#endif\n#if vtkNumComponents == 4\nuniform float mix0;\nuniform float mix1;\nuniform float mix2;\nuniform float mix3;\n#define height0 0.125\n#define height1 0.375\n#define height2 0.625\n#define height3 0.875\n#endif\n#endif\n\n#if vtkNumComponents >= 2\nuniform float oshift1;\nuniform float oscale1;\nuniform float cshift1;\nuniform float cscale1;\n#endif\n#if vtkNumComponents >= 3\nuniform float oshift2;\nuniform float oscale2;\nuniform float cshift2;\nuniform float cscale2;\n#endif\n#if vtkNumComponents >= 4\nuniform float oshift3;\nuniform float oscale3;\nuniform float cshift3;\nuniform float cscale3;\n#endif\n\n// declaration for intermixed geometry\n//VTK::ZBuffer::Dec\n\n// Lighting values\n//VTK::Light::Dec\n\n//=======================================================================\n// Webgl2 specific version of functions\n#if __VERSION__ == 300\n\nuniform highp sampler3D texture1;\n\nvec4 getTextureValue(vec3 pos)\n{\n  vec4 tmp = texture(texture1, pos);\n#if vtkNumComponents == 1\n  tmp.a = tmp.r;\n#endif\n#if vtkNumComponents == 2\n  tmp.a = tmp.g;\n#endif\n#if vtkNumComponents == 3\n  tmp.a = length(tmp.rgb);\n#endif\n  return tmp;\n}\n\n//=======================================================================\n// WebGL1 specific version of functions\n#else\n\nuniform sampler2D texture1;\n\nuniform float texWidth;\nuniform float texHeight;\nuniform int xreps;\nuniform int xstride;\nuniform int ystride;\n\n// if computing triliear values from multiple z slices\n#ifdef vtkTriliearOn\nvec4 getTextureValue(vec3 ijk)\n{\n  float zoff = 1.0/float(volumeDimensions.z);\n  vec4 val1 = getOneTextureValue(ijk);\n  vec4 val2 = getOneTextureValue(vec3(ijk.xy, ijk.z + zoff));\n\n  float indexZ = float(volumeDimensions)*ijk.z;\n  float zmix =  indexZ - floor(indexZ);\n\n  return mix(val1, val2, zmix);\n}\n\nvec4 getOneTextureValue(vec3 ijk)\n#else // nearest or fast linear\nvec4 getTextureValue(vec3 ijk)\n#endif\n{\n  vec3 tdims = vec3(volumeDimensions);\n\n#ifdef debugtile\n  vec2 tpos = vec2(ijk.x, ijk.y);\n  vec4 tmp = texture2D(texture1, tpos);\n  tmp.a = 1.0;\n\n#else\n  int z = int(ijk.z * tdims.z);\n  int yz = z / xreps;\n  int xz = z - yz*xreps;\n\n  int tileWidth = volumeDimensions.x/xstride;\n  int tileHeight = volumeDimensions.y/ystride;\n\n  xz *= tileWidth;\n  yz *= tileHeight;\n\n  float ni = float(xz) + (ijk.x*float(tileWidth));\n  float nj = float(yz) + (ijk.y*float(tileHeight));\n\n  vec2 tpos = vec2(ni/texWidth, nj/texHeight);\n\n  vec4 tmp = texture2D(texture1, tpos);\n\n#if vtkNumComponents == 1\n  tmp.a = tmp.r;\n#endif\n#if vtkNumComponents == 2\n  tmp.g = tmp.a;\n#endif\n#if vtkNumComponents == 3\n  tmp.a = length(tmp.rgb);\n#endif\n#endif\n\n  return tmp;\n}\n\n// End of Webgl1 specific code\n//=======================================================================\n#endif\n\n//=======================================================================\n// compute the normal and gradient magnitude for a position\nvec4 computeNormal(vec3 pos, float scalar, vec3 tstep)\n{\n  vec4 result;\n\n  result.x = getTextureValue(pos + vec3(tstep.x, 0.0, 0.0)).a - scalar;\n  result.y = getTextureValue(pos + vec3(0.0, tstep.y, 0.0)).a - scalar;\n  result.z = getTextureValue(pos + vec3(0.0, 0.0, tstep.z)).a - scalar;\n\n  // divide by spacing\n  result.xyz /= vSpacing;\n\n  result.w = length(result.xyz);\n\n  // rotate to View Coords\n  result.xyz =\n    result.x * vPlaneNormal0 +\n    result.y * vPlaneNormal2 +\n    result.z * vPlaneNormal4;\n\n  if (result.w > 0.0)\n  {\n    result.xyz /= result.w;\n  }\n  return result;\n}\n\n#ifdef vtkImageLabelOutlineOn\nvec3 fragCoordToIndexSpace(vec4 fragCoord) {\n  vec4 pcPos = vec4(\n    (fragCoord.x / vpWidth - 0.5) * 2.0,\n    (fragCoord.y / vpHeight - 0.5) * 2.0,\n    (fragCoord.z - 0.5) * 2.0,\n    1.0);\n\n  vec4 worldCoord = PCWCMatrix * pcPos;\n  vec4 vertex = (worldCoord/worldCoord.w);\n\n  return (vWCtoIDX * vertex).xyz / vec3(volumeDimensions);\n}\n#endif\n\n//=======================================================================\n// compute the normals and gradient magnitudes for a position\n// for independent components\nmat4 computeMat4Normal(vec3 pos, vec4 tValue, vec3 tstep)\n{\n  mat4 result;\n  vec4 distX = getTextureValue(pos + vec3(tstep.x, 0.0, 0.0)) - tValue;\n  vec4 distY = getTextureValue(pos + vec3(0.0, tstep.y, 0.0)) - tValue;\n  vec4 distZ = getTextureValue(pos + vec3(0.0, 0.0, tstep.z)) - tValue;\n\n  // divide by spacing\n  distX /= vSpacing.x;\n  distY /= vSpacing.y;\n  distZ /= vSpacing.z;\n\n  mat3 rot;\n  rot[0] = vPlaneNormal0;\n  rot[1] = vPlaneNormal2;\n  rot[2] = vPlaneNormal4;\n\n#if !defined(vtkComponent0Proportional)\n  result[0].xyz = vec3(distX.r, distY.r, distZ.r);\n  result[0].a = length(result[0].xyz);\n  result[0].xyz *= rot;\n  if (result[0].w > 0.0)\n  {\n    result[0].xyz /= result[0].w;\n  }\n#endif\n\n// optionally compute the 2nd component\n#if vtkNumComponents >= 2 && !defined(vtkComponent1Proportional)\n  result[1].xyz = vec3(distX.g, distY.g, distZ.g);\n  result[1].a = length(result[1].xyz);\n  result[1].xyz *= rot;\n  if (result[1].w > 0.0)\n  {\n    result[1].xyz /= result[1].w;\n  }\n#endif\n\n// optionally compute the 3rd component\n#if vtkNumComponents >= 3 && !defined(vtkComponent2Proportional)\n  result[2].xyz = vec3(distX.b, distY.b, distZ.b);\n  result[2].a = length(result[2].xyz);\n  result[2].xyz *= rot;\n  if (result[2].w > 0.0)\n  {\n    result[2].xyz /= result[2].w;\n  }\n#endif\n\n// optionally compute the 4th component\n#if vtkNumComponents >= 4 && !defined(vtkComponent3Proportional)\n  result[3].xyz = vec3(distX.a, distY.a, distZ.a);\n  result[3].a = length(result[3].xyz);\n  result[3].xyz *= rot;\n  if (result[3].w > 0.0)\n  {\n    result[3].xyz /= result[3].w;\n  }\n#endif\n\n  return result;\n}\n\n//=======================================================================\n// Given a normal compute the gradient opacity factors\n//\nfloat computeGradientOpacityFactor(\n  vec4 normal, float goscale, float goshift, float gomin, float gomax)\n{\n#if defined(vtkGradientOpacityOn)\n  return clamp(normal.a*goscale + goshift, gomin, gomax);\n#else\n  return 1.0;\n#endif\n}\n\n#if vtkLightComplexity > 0\nvoid applyLighting(inout vec3 tColor, vec4 normal)\n{\n  vec3 diffuse = vec3(0.0, 0.0, 0.0);\n  vec3 specular = vec3(0.0, 0.0, 0.0);\n  //VTK::Light::Impl\n  tColor.rgb = tColor.rgb*(diffuse*vDiffuse + vAmbient) + specular*vSpecular;\n}\n#endif\n\n//=======================================================================\n// Given a texture value compute the color and opacity\n//\nvec4 getColorForValue(vec4 tValue, vec3 posIS, vec3 tstep)\n{\n#ifdef vtkImageLabelOutlineOn\n  vec3 centerPosIS = fragCoordToIndexSpace(gl_FragCoord); // pos in texture space\n  vec4 centerValue = getTextureValue(centerPosIS);\n  bool pixelOnBorder = false;\n  vec4 tColor = texture2D(ctexture, vec2(centerValue.r * cscale0 + cshift0, 0.5));\n\n  // Get alpha of segment from opacity function.\n  tColor.a = texture2D(otexture, vec2(centerValue.r * oscale0 + oshift0, 0.5)).r;\n\n  // Only perform outline check on fragments rendering voxels that aren't invisible.\n  // Saves a bunch of needless checks on the background.\n  // TODO define epsilon when building shader?\n  if (float(tColor.a) > 0.01) {\n    for (int i = -outlineThickness; i <= outlineThickness; i++) {\n      for (int j = -outlineThickness; j <= outlineThickness; j++) {\n        if (i == 0 || j == 0) {\n          continue;\n        }\n\n        vec4 neighborPixelCoord = vec4(gl_FragCoord.x + float(i),\n          gl_FragCoord.y + float(j),\n          gl_FragCoord.z, gl_FragCoord.w);\n\n        vec3 neighborPosIS = fragCoordToIndexSpace(neighborPixelCoord);\n        vec4 value = getTextureValue(neighborPosIS);\n\n        // If any of my neighbours are not the same value as I\n        // am, this means I am on the border of the segment.\n        // We can break the loops\n        if (any(notEqual(value, centerValue))) {\n          pixelOnBorder = true;\n          break;\n        }\n      }\n\n      if (pixelOnBorder == true) {\n        break;\n      }\n    }\n\n    // If I am on the border, I am displayed at full opacity\n    if (pixelOnBorder == true) {\n      tColor.a = 1.0;\n    }\n  }\n\n#else\n  // compute the normal and gradient magnitude if needed\n  // We compute it as a vec4 if possible otherwise a mat4\n  //\n  vec4 goFactor = vec4(1.0,1.0,1.0,1.0);\n\n  // compute the normal vectors as needed\n  #if (vtkLightComplexity > 0) || defined(vtkGradientOpacityOn)\n    #if defined(vtkIndependentComponentsOn) && (vtkNumComponents > 1)\n      mat4 normalMat = computeMat4Normal(posIS, tValue, tstep);\n      #if !defined(vtkComponent0Proportional)\n        vec4 normal0 = normalMat[0];\n      #endif\n      #if !defined(vtkComponent1Proportional)\n        vec4 normal1 = normalMat[1];\n      #endif\n      #if vtkNumComponents > 2\n        #if !defined(vtkComponent2Proportional)\n          vec4 normal2 = normalMat[2];\n        #endif\n        #if vtkNumComponents > 3\n          #if !defined(vtkComponent3Proportional)\n            vec4 normal3 = normalMat[3];\n          #endif\n        #endif\n      #endif\n    #else\n      vec4 normal0 = computeNormal(posIS, tValue.a, tstep);\n    #endif\n  #endif\n\n  // compute gradient opacity factors as needed\n  #if defined(vtkGradientOpacityOn)\n    #if !defined(vtkComponent0Proportional)\n      goFactor.x =\n        computeGradientOpacityFactor(normal0, goscale0, goshift0, gomin0, gomax0);\n    #endif\n    #if defined(vtkIndependentComponentsOn) && (vtkNumComponents > 1)\n      #if !defined(vtkComponent1Proportional)\n        goFactor.y =\n          computeGradientOpacityFactor(normal1, goscale1, goshift1, gomin1, gomax1);\n      #endif\n      #if vtkNumComponents > 2\n        #if !defined(vtkComponent2Proportional)\n          goFactor.z =\n            computeGradientOpacityFactor(normal2, goscale2, goshift2, gomin2, gomax2);\n        #endif\n        #if vtkNumComponents > 3\n          #if !defined(vtkComponent3Proportional)\n            goFactor.w =\n              computeGradientOpacityFactor(normal3, goscale3, goshift3, gomin3, gomax3);\n          #endif\n        #endif\n      #endif\n    #endif\n  #endif\n\n  // single component is always independent\n  #if vtkNumComponents == 1\n    vec4 tColor = texture2D(ctexture, vec2(tValue.r * cscale0 + cshift0, 0.5));\n    tColor.a = goFactor.x*texture2D(otexture, vec2(tValue.r * oscale0 + oshift0, 0.5)).r;\n  #endif\n\n  #if defined(vtkIndependentComponentsOn) && vtkNumComponents >= 2\n    vec4 tColor = mix0*texture2D(ctexture, vec2(tValue.r * cscale0 + cshift0, height0));\n    #if !defined(vtkComponent0Proportional)\n      tColor.a = goFactor.x*mix0*texture2D(otexture, vec2(tValue.r * oscale0 + oshift0, height0)).r;\n    #else\n      float pwfValue = texture2D(otexture, vec2(tValue.r * oscale0 + oshift0, height0)).r;\n      tColor *= pwfValue;\n      tColor.a *= mix(pwfValue, 1.0, (1.0 - mix0));\n    #endif\n\n    vec3 tColor1 = mix1*texture2D(ctexture, vec2(tValue.g * cscale1 + cshift1, height1)).rgb;\n    #if !defined(vtkComponent1Proportional)\n      tColor.a += goFactor.y*mix1*texture2D(otexture, vec2(tValue.g * oscale1 + oshift1, height1)).r;\n    #else\n      float pwfValue = texture2D(otexture, vec2(tValue.g * oscale1 + oshift1, height1)).r;\n      tColor1 *= pwfValue;\n      tColor.a *= mix(pwfValue, 1.0, (1.0 - mix1));\n    #endif\n\n    #if vtkNumComponents >= 3\n      vec3 tColor2 = mix2*texture2D(ctexture, vec2(tValue.b * cscale2 + cshift2, height2)).rgb;\n      #if !defined(vtkComponent2Proportional)\n        tColor.a += goFactor.z*mix2*texture2D(otexture, vec2(tValue.b * oscale2 + oshift2, height2)).r;\n      #else\n        float pwfValue = texture2D(otexture, vec2(tValue.b * oscale2 + oshift2, height2)).r;\n        tColor2 *= pwfValue;\n        tColor.a *= mix(pwfValue, 1.0, (1.0 - mix2));\n      #endif\n\n      #if vtkNumComponents >= 4\n        vec3 tColor3 = mix3*texture2D(ctexture, vec2(tValue.a * cscale3 + cshift3, height3)).rgb;\n        #if !defined(vtkComponent3Proportional)\n          tColor.a += goFactor.w*mix3*texture2D(otexture, vec2(tValue.a * oscale3 + oshift3, height3)).r;\n        #else\n          float pwfValue = texture2D(otexture, vec2(tValue.a * oscale3 + oshift3, height3)).r;\n          tColor3 *= pwfValue;\n          tColor.a *= mix(pwfValue, 1.0, (1.0 - mix3));\n        #endif\n      #endif\n    #endif\n  #else // then not independent\n\n  #if vtkNumComponents == 2\n    float lum = tValue.r * cscale0 + cshift0;\n    float alpha = goFactor.x*texture2D(otexture, vec2(tValue.a * oscale1 + oshift1, 0.5)).r;\n    vec4 tColor = vec4(lum, lum, lum, alpha);\n  #endif\n  #if vtkNumComponents == 3\n    vec4 tColor;\n    tColor.r = tValue.r * cscale0 + cshift0;\n    tColor.g = tValue.g * cscale1 + cshift1;\n    tColor.b = tValue.b * cscale2 + cshift2;\n    tColor.a = goFactor.x*texture2D(otexture, vec2(tValue.a * oscale0 + oshift0, 0.5)).r;\n  #endif\n  #if vtkNumComponents == 4\n    vec4 tColor;\n    tColor.r = tValue.r * cscale0 + cshift0;\n    tColor.g = tValue.g * cscale1 + cshift1;\n    tColor.b = tValue.b * cscale2 + cshift2;\n    tColor.a = goFactor.x*texture2D(otexture, vec2(tValue.a * oscale3 + oshift3, 0.5)).r;\n  #endif\n  #endif // dependent\n\n  // apply lighting if requested as appropriate\n  #if vtkLightComplexity > 0\n    #if !defined(vtkComponent0Proportional)\n      applyLighting(tColor.rgb, normal0);\n    #endif\n  #if defined(vtkIndependentComponentsOn) && vtkNumComponents >= 2\n    #if !defined(vtkComponent1Proportional)\n      applyLighting(tColor1, normal1);\n    #endif\n  #if vtkNumComponents >= 3\n    #if !defined(vtkComponent2Proportional)\n      applyLighting(tColor2, normal2);\n    #endif\n  #if vtkNumComponents >= 4\n    #if !defined(vtkComponent3Proportional)\n      applyLighting(tColor3, normal3);\n    #endif\n  #endif\n  #endif\n  #endif\n#endif\n\n// perform final independent blend as needed\n#if defined(vtkIndependentComponentsOn) && vtkNumComponents >= 2\n  tColor.rgb += tColor1;\n#if vtkNumComponents >= 3\n  tColor.rgb += tColor2;\n#if vtkNumComponents >= 4\n  tColor.rgb += tColor3;\n#endif\n#endif\n#endif\n\n#endif\n\n\n\n\n\n\n\nreturn tColor;\n}\n\nbool valueWithinScalarRange(vec4 val, vec4 min, vec4 max) {\n  bool withinRange = false;\n  #if vtkNumComponents == 1\n    if (val.r >= min.r && val.r <= max.r) {\n      withinRange = true;\n    }\n  #endif\n  #if defined(vtkIndependentComponentsOn) && vtkNumComponents == 2\n     if (val.r >= min.r && val.r <= max.r &&\n        val.g >= min.g && val.g <= max.g) {\n      withinRange = true;\n    }\n  #endif\n  #if defined(vtkIndependentComponentsOn) && vtkNumComponents >= 3\n    if (all(greaterThanEqual(val, ipScalarRangeMin)) &&\n        all(lessThanEqual(val, ipScalarRangeMax))) {\n      withinRange = true;\n    }\n  #endif\n  return withinRange;\n}\n\n//=======================================================================\n// Apply the specified blend mode operation along the ray's path.\n//\nvoid applyBlend(vec3 posIS, vec3 endIS, float sampleDistanceIS, vec3 tdims)\n{\n  vec3 tstep = 1.0/tdims;\n\n  // start slightly inside and apply some jitter\n  vec3 delta = endIS - posIS;\n  vec3 stepIS = normalize(delta)*sampleDistanceIS;\n  float raySteps = length(delta)/sampleDistanceIS;\n\n  // avoid 0.0 jitter\n  float jitter = 0.01 + 0.99*texture2D(jtexture, gl_FragCoord.xy/32.0).r;\n  float stepsTraveled = jitter;\n\n  // local vars for the loop\n  vec4 color = vec4(0.0, 0.0, 0.0, 0.0);\n  vec4 tValue;\n  vec4 tColor;\n\n  // if we have less than one step then pick the middle point\n  // as our value\n  // if (raySteps <= 1.0)\n  // {\n  //   posIS = (posIS + endIS)*0.5;\n  // }\n\n  // Perform initial step at the volume boundary\n  // compute the scalar\n  tValue = getTextureValue(posIS);\n\n  #if vtkBlendMode == 0 // COMPOSITE_BLEND\n    // now map through opacity and color\n    tColor = getColorForValue(tValue, posIS, tstep);\n\n    // handle very thin volumes\n    if (raySteps <= 1.0)\n    {\n      tColor.a = 1.0 - pow(1.0 - tColor.a, raySteps);\n      gl_FragData[0] = tColor;\n      return;\n    }\n\n    tColor.a = 1.0 - pow(1.0 - tColor.a, jitter);\n    color = vec4(tColor.rgb*tColor.a, tColor.a);\n    posIS += (jitter*stepIS);\n\n    for (int i = 0; i < //VTK::MaximumSamplesValue ; ++i)\n    {\n      if (stepsTraveled + 1.0 >= raySteps) { break; }\n\n      // compute the scalar\n      tValue = getTextureValue(posIS);\n\n      // now map through opacity and color\n      tColor = getColorForValue(tValue, posIS, tstep);\n\n      float mix = (1.0 - color.a);\n\n      // this line should not be needed but nvidia seems to not handle\n      // the break correctly on windows/chrome 58 angle\n      //mix = mix * sign(max(raySteps - stepsTraveled - 1.0, 0.0));\n\n      color = color + vec4(tColor.rgb*tColor.a, tColor.a)*mix;\n      stepsTraveled++;\n      posIS += stepIS;\n      if (color.a > 0.99) { color.a = 1.0; break; }\n    }\n\n    if (color.a < 0.99 && (raySteps - stepsTraveled) > 0.0)\n    {\n      posIS = endIS;\n\n      // compute the scalar\n      tValue = getTextureValue(posIS);\n\n      // now map through opacity and color\n      tColor = getColorForValue(tValue, posIS, tstep);\n      tColor.a = 1.0 - pow(1.0 - tColor.a, raySteps - stepsTraveled);\n\n      float mix = (1.0 - color.a);\n      color = color + vec4(tColor.rgb*tColor.a, tColor.a)*mix;\n    }\n\n    gl_FragData[0] = vec4(color.rgb/color.a, color.a);\n  #endif\n  #if vtkBlendMode == 1 || vtkBlendMode == 2\n    // MAXIMUM_INTENSITY_BLEND || MINIMUM_INTENSITY_BLEND\n    // Find maximum/minimum intensity along the ray.\n\n    // Define the operation we will use (min or max)\n    #if vtkBlendMode == 1\n    #define OP max\n    #else\n    #define OP min\n    #endif\n\n    // If the clipping range is shorter than the sample distance\n    // we can skip the sampling loop along the ray.\n    if (raySteps <= 1.0)\n    {\n      gl_FragData[0] = getColorForValue(tValue, posIS, tstep);\n      return;\n    }\n\n    vec4 value = tValue;\n    posIS += (jitter*stepIS);\n\n    // Sample along the ray until MaximumSamplesValue,\n    // ending slightly inside the total distance\n    for (int i = 0; i < //VTK::MaximumSamplesValue ; ++i)\n    {\n      // If we have reached the last step, break\n      if (stepsTraveled + 1.0 >= raySteps) { break; }\n\n      // compute the scalar\n      tValue = getTextureValue(posIS);\n\n      // Update the maximum value if necessary\n      value = OP(tValue, value);\n\n      // Otherwise, continue along the ray\n      stepsTraveled++;\n      posIS += stepIS;\n    }\n\n    // Perform the last step along the ray using the\n    // residual distance\n    posIS = endIS;\n    tValue = getTextureValue(posIS);\n    value = OP(tValue, value);\n\n    // Now map through opacity and color\n    gl_FragData[0] = getColorForValue(value, posIS, tstep);\n  #endif\n  #if vtkBlendMode == 3 || vtkBlendMode == 4 //AVERAGE_INTENSITY_BLEND || ADDITIVE_BLEND\n    vec4 ipScalarRangeMin = vec4 (\n      //VTK::IPScalarRangeMin,\n      //VTK::IPScalarRangeMin,\n      //VTK::IPScalarRangeMin,\n      //VTK::IPScalarRangeMax);\n    vec4 ipScalarRangeMax = vec4(\n      //VTK::IPScalarRangeMax,\n      //VTK::IPScalarRangeMax,\n      //VTK::IPScalarRangeMax,\n      //VTK::IPScalarRangeMax);\n\n    vec4 sum = vec4(0.);\n\n    if (valueWithinScalarRange(tValue, ipScalarRangeMin, ipScalarRangeMax)) {\n      sum += tValue;\n    }\n\n    if (raySteps <= 1.0) {\n      gl_FragData[0] = getColorForValue(sum, posIS, tstep);\n      return;\n    }\n\n    posIS += (jitter*stepIS);\n\n    // Sample along the ray until MaximumSamplesValue,\n    // ending slightly inside the total distance\n    for (int i = 0; i < //VTK::MaximumSamplesValue ; ++i)\n    {\n      // If we have reached the last step, break\n      if (stepsTraveled + 1.0 >= raySteps) { break; }\n\n      // compute the scalar\n      tValue = getTextureValue(posIS);\n\n      // One can control the scalar range by setting the AverageIPScalarRange to disregard scalar values, not in the range of interest, from the average computation.\n      // Notes:\n      // - We are comparing all values in the texture to see if any of them\n      //   are outside of the scalar range. In the future we might want to allow\n      //   scalar ranges for each component.\n      if (valueWithinScalarRange(tValue, ipScalarRangeMin, ipScalarRangeMax)) {\n        // Sum the values across each step in the path\n        sum += tValue;\n      }\n      stepsTraveled++;\n      posIS += stepIS;\n    }\n\n    // Perform the last step along the ray using the\n    // residual distance\n    posIS = endIS;\n\n    // compute the scalar\n    tValue = getTextureValue(posIS);\n\n    // One can control the scalar range by setting the IPScalarRange to disregard scalar values, not in the range of interest, from the average computation\n    if (valueWithinScalarRange(tValue, ipScalarRangeMin, ipScalarRangeMax)) {\n      sum += tValue;\n\n      stepsTraveled++;\n    }\n\n    #if vtkBlendMode == 3 // Average\n      sum /= vec4(stepsTraveled, stepsTraveled, stepsTraveled, 1.0);\n    #endif\n\n    gl_FragData[0] = getColorForValue(sum, posIS, tstep);\n  #endif\n}\n\n//=======================================================================\n// Compute a new start and end point for a given ray based\n// on the provided bounded clipping plane (aka a rectangle)\nvoid getRayPointIntersectionBounds(\n  vec3 rayPos, vec3 rayDir,\n  vec3 planeDir, float planeDist,\n  inout vec2 tbounds, vec3 vPlaneX, vec3 vPlaneY,\n  float vSize1, float vSize2)\n{\n  float result = dot(rayDir, planeDir);\n  if (result == 0.0)\n  {\n    return;\n  }\n  result = -1.0 * (dot(rayPos, planeDir) + planeDist) / result;\n  vec3 xposVC = rayPos + rayDir*result;\n  vec3 vxpos = xposVC - vOriginVC;\n  vec2 vpos = vec2(\n    dot(vxpos, vPlaneX),\n    dot(vxpos, vPlaneY));\n\n  // on some apple nvidia systems this does not work\n  // if (vpos.x < 0.0 || vpos.x > vSize1 ||\n  //     vpos.y < 0.0 || vpos.y > vSize2)\n  // even just\n  // if (vpos.x < 0.0 || vpos.y < 0.0)\n  // fails\n  // so instead we compute a value that represents in and out\n  //and then compute the return using this value\n  float xcheck = max(0.0, vpos.x * (vpos.x - vSize1)); //  0 means in bounds\n  float check = sign(max(xcheck, vpos.y * (vpos.y - vSize2))); //  0 means in bounds, 1 = out\n\n  tbounds = mix(\n   vec2(min(tbounds.x, result), max(tbounds.y, result)), // in value\n   tbounds, // out value\n   check);  // 0 in 1 out\n}\n\n//=======================================================================\n// given a\n// - ray direction (rayDir)\n// - starting point (vertexVCVSOutput)\n// - bounding planes of the volume\n// - optionally depth buffer values\n// - far clipping plane\n// compute the start/end distances of the ray we need to cast\nvec2 computeRayDistances(vec3 rayDir, vec3 tdims)\n{\n  vec2 dists = vec2(100.0*camFar, -1.0);\n\n  vec3 vSize = vSpacing*(tdims - 1.0);\n\n  // all this is in View Coordinates\n  getRayPointIntersectionBounds(vertexVCVSOutput, rayDir,\n    vPlaneNormal0, vPlaneDistance0, dists, vPlaneNormal2, vPlaneNormal4,\n    vSize.y, vSize.z);\n  getRayPointIntersectionBounds(vertexVCVSOutput, rayDir,\n    vPlaneNormal1, vPlaneDistance1, dists, vPlaneNormal2, vPlaneNormal4,\n    vSize.y, vSize.z);\n  getRayPointIntersectionBounds(vertexVCVSOutput, rayDir,\n    vPlaneNormal2, vPlaneDistance2, dists, vPlaneNormal0, vPlaneNormal4,\n    vSize.x, vSize.z);\n  getRayPointIntersectionBounds(vertexVCVSOutput, rayDir,\n    vPlaneNormal3, vPlaneDistance3, dists, vPlaneNormal0, vPlaneNormal4,\n    vSize.x, vSize.z);\n  getRayPointIntersectionBounds(vertexVCVSOutput, rayDir,\n    vPlaneNormal4, vPlaneDistance4, dists, vPlaneNormal0, vPlaneNormal2,\n    vSize.x, vSize.y);\n  getRayPointIntersectionBounds(vertexVCVSOutput, rayDir,\n    vPlaneNormal5, vPlaneDistance5, dists, vPlaneNormal0, vPlaneNormal2,\n    vSize.x, vSize.y);\n\n  //VTK::ClipPlane::Impl\n\n  // do not go behind front clipping plane\n  dists.x = max(0.0,dists.x);\n\n  // do not go PAST far clipping plane\n  float farDist = -camThick/rayDir.z;\n  dists.y = min(farDist,dists.y);\n\n  // Do not go past the zbuffer value if set\n  // This is used for intermixing opaque geometry\n  //VTK::ZBuffer::Impl\n\n  return dists;\n}\n\n//=======================================================================\n// Compute the index space starting position (pos) and end\n// position\n//\nvoid computeIndexSpaceValues(out vec3 pos, out vec3 endPos, out float sampleDistanceIS, vec3 rayDir, vec2 dists)\n{\n  // compute starting and ending values in volume space\n  pos = vertexVCVSOutput + dists.x*rayDir;\n  pos = pos - vOriginVC;\n  // convert to volume basis and origin\n  pos = vec3(\n    dot(pos, vPlaneNormal0),\n    dot(pos, vPlaneNormal2),\n    dot(pos, vPlaneNormal4));\n\n  endPos = vertexVCVSOutput + dists.y*rayDir;\n  endPos = endPos - vOriginVC;\n  endPos = vec3(\n    dot(endPos, vPlaneNormal0),\n    dot(endPos, vPlaneNormal2),\n    dot(endPos, vPlaneNormal4));\n\n  float delta = length(endPos - pos);\n\n  pos *= vVCToIJK;\n  endPos *= vVCToIJK;\n\n  float delta2 = length(endPos - pos);\n  sampleDistanceIS = sampleDistance*delta2/delta;\n}\n\nvoid main()\n{\n\n  vec3 rayDirVC;\n\n  if (cameraParallel == 1)\n  {\n    // Camera is parallel, so the rayDir is just the direction of the camera.\n    rayDirVC = vec3(0.0, 0.0, -1.0);\n  } else {\n    // camera is at 0,0,0 so rayDir for perspective is just the vc coord\n    rayDirVC = normalize(vertexVCVSOutput);\n  }\n\n  vec3 tdims = vec3(volumeDimensions);\n\n  // compute the start and end points for the ray\n  vec2 rayStartEndDistancesVC = computeRayDistances(rayDirVC, tdims);\n\n  // do we need to composite? aka does the ray have any length\n  // If not, bail out early\n  if (rayStartEndDistancesVC.y <= rayStartEndDistancesVC.x)\n  {\n    discard;\n  }\n\n  // IS = Index Space\n  vec3 posIS;\n  vec3 endIS;\n  float sampleDistanceIS;\n  computeIndexSpaceValues(posIS, endIS, sampleDistanceIS, rayDirVC, rayStartEndDistancesVC);\n\n  // Perform the blending operation along the ray\n  applyBlend(posIS, endIS, sampleDistanceIS, tdims);\n}\n";

export { vtkVolumeFS as v };