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