/** * @author huwb / http://huwbowles.com/ * * God-rays (crepuscular rays) * * Similar implementation to the one used by Crytek for CryEngine 2 [Sousa2008]. * Blurs a mask generated from the depth map along radial lines emanating from the light * source. The blur repeatedly applies a blur filter of increasing support but constant * sample count to produce a blur filter with large support. * * My implementation performs 3 passes, similar to the implementation from Sousa. I found * just 6 samples per pass produced acceptible results. The blur is applied three times, * with decreasing filter support. The result is equivalent to a single pass with * 6*6*6 = 216 samples. * * References: * * Sousa2008 - Crysis Next Gen Effects, GDC2008, http://www.crytek.com/sites/default/files/GDC08_SousaT_CrysisEffects.ppt */ THREE.ShaderGodRays = { /** * The god-ray generation shader. * * First pass: * * The input is the depth map. I found that the output from the * THREE.MeshDepthMaterial material was directly suitable without * requiring any treatment whatsoever. * * The depth map is blurred along radial lines towards the "sun". The * output is written to a temporary render target (I used a 1/4 sized * target). * * Pass two & three: * * The results of the previous pass are re-blurred, each time with a * decreased distance between samples. */ 'godrays_generate': { uniforms: { tInput: { type: "t", value: null }, fStepSize: { type: "f", value: 1.0 }, vSunPositionScreenSpace: { type: "v2", value: new THREE.Vector2( 0.5, 0.5 ) } }, vertexShader: [ "varying vec2 vUv;", "void main() {", "vUv = uv;", "gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );", "}" ].join("\n"), fragmentShader: [ "#define TAPS_PER_PASS 6.0", "varying vec2 vUv;", "uniform sampler2D tInput;", "uniform vec2 vSunPositionScreenSpace;", "uniform float fStepSize;", // filter step size "void main() {", // delta from current pixel to "sun" position "vec2 delta = vSunPositionScreenSpace - vUv;", "float dist = length( delta );", // Step vector (uv space) "vec2 stepv = fStepSize * delta / dist;", // Number of iterations between pixel and sun "float iters = dist/fStepSize;", "vec2 uv = vUv.xy;", "float col = 0.0;", // This breaks ANGLE in Chrome 22 // - see http://code.google.com/p/chromium/issues/detail?id=153105 /* // Unrolling didnt do much on my hardware (ATI Mobility Radeon 3450), // so i've just left the loop "for ( float i = 0.0; i < TAPS_PER_PASS; i += 1.0 ) {", // Accumulate samples, making sure we dont walk past the light source. // The check for uv.y < 1 would not be necessary with "border" UV wrap // mode, with a black border colour. I don't think this is currently // exposed by three.js. As a result there might be artifacts when the // sun is to the left, right or bottom of screen as these cases are // not specifically handled. "col += ( i <= iters && uv.y < 1.0 ? texture2D( tInput, uv ).r : 0.0 );", "uv += stepv;", "}", */ // Unrolling loop manually makes it work in ANGLE "if ( 0.0 <= iters && uv.y < 1.0 ) col += texture2D( tInput, uv ).r;", "uv += stepv;", "if ( 1.0 <= iters && uv.y < 1.0 ) col += texture2D( tInput, uv ).r;", "uv += stepv;", "if ( 2.0 <= iters && uv.y < 1.0 ) col += texture2D( tInput, uv ).r;", "uv += stepv;", "if ( 3.0 <= iters && uv.y < 1.0 ) col += texture2D( tInput, uv ).r;", "uv += stepv;", "if ( 4.0 <= iters && uv.y < 1.0 ) col += texture2D( tInput, uv ).r;", "uv += stepv;", "if ( 5.0 <= iters && uv.y < 1.0 ) col += texture2D( tInput, uv ).r;", "uv += stepv;", // Should technically be dividing by 'iters', but 'TAPS_PER_PASS' smooths out // objectionable artifacts, in particular near the sun position. The side // effect is that the result is darker than it should be around the sun, as // TAPS_PER_PASS is greater than the number of samples actually accumulated. // When the result is inverted (in the shader 'godrays_combine', this produces // a slight bright spot at the position of the sun, even when it is occluded. "gl_FragColor = vec4( col/TAPS_PER_PASS );", "gl_FragColor.a = 1.0;", "}" ].join("\n") }, /** * Additively applies god rays from texture tGodRays to a background (tColors). * fGodRayIntensity attenuates the god rays. */ 'godrays_combine': { uniforms: { tColors: { type: "t", value: null }, tGodRays: { type: "t", value: null }, fGodRayIntensity: { type: "f", value: 0.69 }, vSunPositionScreenSpace: { type: "v2", value: new THREE.Vector2( 0.5, 0.5 ) } }, vertexShader: [ "varying vec2 vUv;", "void main() {", "vUv = uv;", "gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );", "}" ].join("\n"), fragmentShader: [ "varying vec2 vUv;", "uniform sampler2D tColors;", "uniform sampler2D tGodRays;", "uniform vec2 vSunPositionScreenSpace;", "uniform float fGodRayIntensity;", "void main() {", // Since THREE.MeshDepthMaterial renders foreground objects white and background // objects black, the god-rays will be white streaks. Therefore value is inverted // before being combined with tColors "gl_FragColor = texture2D( tColors, vUv ) + fGodRayIntensity * vec4( 1.0 - texture2D( tGodRays, vUv ).r );", "gl_FragColor.a = 1.0;", "}" ].join("\n") }, /** * A dodgy sun/sky shader. Makes a bright spot at the sun location. Would be * cheaper/faster/simpler to implement this as a simple sun sprite. */ 'godrays_fake_sun': { uniforms: { vSunPositionScreenSpace: { type: "v2", value: new THREE.Vector2( 0.5, 0.5 ) }, fAspect: { type: "f", value: 1.0 }, sunColor: { type: "c", value: new THREE.Color( 0xffee00 ) }, bgColor: { type: "c", value: new THREE.Color( 0x000000 ) } }, vertexShader: [ "varying vec2 vUv;", "void main() {", "vUv = uv;", "gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );", "}" ].join("\n"), fragmentShader: [ "varying vec2 vUv;", "uniform vec2 vSunPositionScreenSpace;", "uniform float fAspect;", "uniform vec3 sunColor;", "uniform vec3 bgColor;", "void main() {", "vec2 diff = vUv - vSunPositionScreenSpace;", // Correct for aspect ratio "diff.x *= fAspect;", "float prop = clamp( length( diff ) / 0.5, 0.0, 1.0 );", "prop = 0.35 * pow( 1.0 - prop, 3.0 );", "gl_FragColor.xyz = mix( sunColor, bgColor, 1.0 - prop );", "gl_FragColor.w = 1.0;", "}" ].join("\n") } };