playcanvas/build/playcanvas/src/scene/shader-lib/glsl/chunks/render-pass/frag/volumetricFog.d.ts

Open-source WebGL/WebGPU 3D engine for the web

declare const _default: "\n    #include \"screenDepthPS\"\n\n    varying vec2 uv0;\n\n    uniform vec3 uFogCameraPos;\n    uniform vec3 uFogCameraFwd;\n    uniform mat4 uFogInvView;\n    uniform vec2 uFogProjScale;\n    uniform vec3 uFogTint;\n    uniform vec3 uFogLightColor;\n    uniform vec3 uFogLightDir;      // world space direction towards the light\n    uniform vec3 uFogAmbient;\n    uniform vec4 uFogParams;        // x: density, y: height base, z: height falloff, w: max distance\n    uniform vec4 uFogScatterParams; // x: anisotropy, y: step count, z: temporal noise offset, w: shadow intensity\n\n    #ifdef FOG_SHADOWS\n        uniform mat4 uFogShadowMatrixPalette[4];\n        uniform vec4 uFogShadowCascadeDistances;\n        uniform vec4 uFogShadowParams; // x: cascade count, y: bias, z: unused, w: max shadow distance\n        #ifdef FOG_SHADOW_PCF\n            uniform sampler2DShadow uFogShadowMap;\n        #else\n            uniform sampler2D uFogShadowMap;\n        #endif\n\n        float sampleFogShadow(vec3 worldPos, float viewDepth) {\n\n            // no shadow past the shadow distance\n            if (viewDepth >= uFogShadowParams.w) return 1.0;\n\n            // cascade index based on the view depth\n            vec4 comparisons = step(uFogShadowCascadeDistances, vec4(viewDepth));\n            int cascadeIndex = int(min(dot(comparisons, vec4(1.0)), uFogShadowParams.x - 1.0));\n\n            vec3 shadowCoord = (uFogShadowMatrixPalette[cascadeIndex] * vec4(worldPos, 1.0)).xyz;\n            float z = shadowCoord.z - uFogShadowParams.y;\n\n            #ifdef FOG_SHADOW_PCF\n                // hardware comparison on the depth format shadow map\n                return textureShadow(uFogShadowMap, vec3(shadowCoord.xy, z));\n            #else\n                // manual comparison on the color format shadow map storing depth (PCSS / VSM)\n                return step(z, texture2D(uFogShadowMap, shadowCoord.xy).r);\n            #endif\n        }\n    #endif\n\n    // interleaved gradient noise\n    float fogNoise(vec2 fragCoord) {\n        const vec3 magic = vec3(0.06711056, 0.00583715, 52.9829189);\n        return fract(magic.z * fract(dot(fragCoord, magic.xy)));\n    }\n\n    // normalized Henyey-Greenstein phase function\n    float fogPhase(float cosTheta, float g) {\n        float g2 = g * g;\n        float denom = 1.0 + g2 - 2.0 * g * cosTheta;\n        return (1.0 - g2) / (12.56637 * denom * sqrt(denom));\n    }\n\n    void main() {\n\n        // world space ray for this pixel (perspective projection). Note that uv0 addresses\n        // textures (getImageEffectUV flips it on WebGPU), so undo the flip to get NDC\n        vec2 ndcUV = uv0;\n        #ifdef WEBGPU\n            ndcUV.y = 1.0 - ndcUV.y;\n        #endif\n        vec2 ndc = ndcUV * 2.0 - 1.0;\n        vec3 rayDir = normalize((uFogInvView * vec4(ndc * uFogProjScale, -1.0, 0.0)).xyz);\n\n        // distance along the ray to the scene surface\n        float rayDot = max(dot(rayDir, uFogCameraFwd), 0.001);\n        float rayLength = min(getLinearScreenDepth(uv0) / rayDot, uFogParams.w);\n\n        float stepCount = uFogScatterParams.y;\n        float dt = rayLength / stepCount;\n\n        // per-pixel noise offsets the samples along the ray to hide banding, and cycles over\n        // frames when TAA is used to temporally accumulate to a smooth result\n        float noise = fract(fogNoise(gl_FragCoord.xy) + uFogScatterParams.z);\n\n        // single phase function evaluation, as the light direction is constant along the ray\n        vec3 sunLight = uFogLightColor * fogPhase(dot(rayDir, uFogLightDir), uFogScatterParams.x);\n\n        vec3 inscatter = vec3(0.0);\n        float transmittance = 1.0;\n\n        for (float i = 0.0; i < stepCount; i += 1.0) {\n            float t = (i + noise) * dt;\n            vec3 pos = uFogCameraPos + rayDir * t;\n\n            // exponential height fog density, constant below the base height\n            float density = uFogParams.x * exp(-uFogParams.z * max(pos.y - uFogParams.y, 0.0));\n\n            float shadow = 1.0;\n            #ifdef FOG_SHADOWS\n                shadow = mix(1.0, sampleFogShadow(pos, t * rayDot), uFogScatterParams.w);\n            #endif\n\n            // accumulate in-scattered light and update transmittance (Beer-Lambert)\n            vec3 radiance = sunLight * shadow + uFogAmbient;\n            inscatter += transmittance * uFogTint * radiance * (density * dt);\n            transmittance *= exp(-density * dt);\n\n            if (transmittance < 0.005) break;\n        }\n\n        gl_FragColor = vec4(inscatter, transmittance);\n    }\n";
export default _default;