IridescenceDiffraction chunk converted to WGSL (#7611)

Co-authored-by: Martin Valigursky <[email protected]>

Author: mvaligursky

src/scene/shader-lib/chunks-wgsl/chunks-wgsl.js

@@ -54,7 +54,7 @@ import glossPS from './standard/frag/gloss.js';
 // import gsplatVS from './gsplat/vert/gsplat.js';
 import immediateLinePS from './internal/frag/immediateLine.js';
 import immediateLineVS from './internal/vert/immediateLine.js';
-// import iridescenceDiffractionPS from './lit/frag/iridescenceDiffraction.js';
+import iridescenceDiffractionPS from './lit/frag/iridescenceDiffraction.js';
 import iridescencePS from './standard/frag/iridescence.js';
 import iridescenceThicknessPS from './standard/frag/iridescenceThickness.js';
 import iorPS from './standard/frag/ior.js';
@@ -262,7 +262,7 @@ const shaderChunksWGSL = {
     // gsplatVS,
     immediateLinePS,
     immediateLineVS,
-    // iridescenceDiffractionPS,
+    iridescenceDiffractionPS,
     iridescencePS,
     iridescenceThicknessPS,
     iorPS,

src/scene/shader-lib/chunks-wgsl/lit/frag/iridescenceDiffraction.js

@@ -0,0 +1,103 @@
+export default /* wgsl */`
+uniform material_iridescenceRefractionIndex: f32;
+
+fn iridescence_iorToFresnelScalar(transmittedIor: f32, incidentIor: f32) -> f32 {
+    return pow((transmittedIor - incidentIor) / (transmittedIor + incidentIor), 2.0);
+}
+
+fn iridescence_iorToFresnelVec3(transmittedIor: vec3f, incidentIor: f32) -> vec3f {
+    return pow((transmittedIor - vec3f(incidentIor)) / (transmittedIor + vec3f(incidentIor)), vec3f(2.0));
+}
+
+fn iridescence_fresnelToIor(f0: vec3f) -> vec3f {
+    let sqrtF0: vec3f = sqrt(f0);
+    return (vec3f(1.0) + sqrtF0) / (vec3f(1.0) - sqrtF0);
+}
+
+const XYZ_TO_REC709: mat3x3f = mat3x3f(
+    vec3f(3.2404542, -1.5371385, -0.4985314),
+    vec3f(-0.9692660,  1.8760108,  0.0415560),
+    vec3f(0.0556434, -0.2040259,  1.0572252)
+);
+
+fn iridescence_sensitivity(opd: f32, shift: vec3f) -> vec3f {
+    let PI: f32 = 3.141592653589793;
+    let phase: f32 = 2.0 * PI * opd * 1.0e-9;
+    const val: vec3f = vec3f(5.4856e-13, 4.4201e-13, 5.2481e-13);
+    const pos: vec3f = vec3f(1.6810e+06, 1.7953e+06, 2.2084e+06);
+    const var_: vec3f = vec3f(4.3278e+09, 9.3046e+09, 6.6121e+09);
+
+    var xyz: vec3f = val * sqrt(2.0 * PI * var_) * cos(pos * phase + shift) * exp(-pow(phase, 2.0) * var_);
+    xyz.x = xyz.x + 9.7470e-14 * sqrt(2.0 * PI * 4.5282e+09) * cos(2.2399e+06 * phase + shift[0]) * exp(-4.5282e+09 * pow(phase, 2.0));
+    xyz = xyz / vec3f(1.0685e-07);
+
+    return XYZ_TO_REC709 * xyz;
+}
+
+fn iridescence_fresnelScalar(cosTheta: f32, f0: f32) -> f32 {
+    let x: f32 = clamp(1.0 - cosTheta, 0.0, 1.0);
+    let x2: f32 = x * x;
+    let x5: f32 = x * x2 * x2;
+    return f0 + (1.0 - f0) * x5;
+}
+
+fn iridescence_fresnelVec3(cosTheta: f32, f0: vec3f) -> vec3f {
+    let x: f32 = clamp(1.0 - cosTheta, 0.0, 1.0);
+    let x2: f32 = x * x;
+    let x5: f32 = x * x2 * x2;
+    return f0 + (vec3f(1.0) - f0) * x5;
+}
+
+fn calcIridescence(outsideIor: f32, cosTheta: f32, base_f0: vec3f, iridescenceThickness: f32) -> vec3f {
+    let PI: f32 = 3.141592653589793;
+
+    let iridescenceIor: f32 = mix(outsideIor, uniform.material_iridescenceRefractionIndex, smoothstep(0.0, 0.03, iridescenceThickness));
+    let sinTheta2Sq: f32 = pow(outsideIor / iridescenceIor, 2.0) * (1.0 - pow(cosTheta, 2.0));
+    let cosTheta2Sq: f32 = 1.0 - sinTheta2Sq;
+
+    if (cosTheta2Sq < 0.0) {
+        return vec3f(1.0);
+    }
+
+    let cosTheta2: f32 = sqrt(cosTheta2Sq);
+
+    let r0: f32 = iridescence_iorToFresnelScalar(iridescenceIor, outsideIor);
+    let r12: f32 = iridescence_fresnelScalar(cosTheta, r0);
+    let r21: f32 = r12;
+    let t121: f32 = 1.0 - r12;
+
+    let phi12: f32 = select(0.0, PI, iridescenceIor < outsideIor);
+    let phi21: f32 = PI - phi12;
+
+    let baseIor: vec3f = iridescence_fresnelToIor(base_f0 + vec3f(0.0001));
+    let r1: vec3f = iridescence_iorToFresnelVec3(baseIor, iridescenceIor);
+    let r23: vec3f = iridescence_fresnelVec3(cosTheta2, r1);
+
+    let phi23: vec3f = select(vec3f(0.0), vec3f(PI), baseIor < vec3f(iridescenceIor));
+    let opd: f32 = 2.0 * iridescenceIor * iridescenceThickness * cosTheta2;
+    let phi: vec3f = vec3f(phi21) + phi23; // Promote scalar phi21 to vec3f
+
+    let r123Sq: vec3f = clamp(vec3f(r12) * r23, vec3f(1e-5), vec3f(0.9999));
+    let r123: vec3f = sqrt(r123Sq);
+    let rs: vec3f = pow(vec3f(t121), vec3f(2.0)) * r23 / (vec3f(1.0) - r123Sq);
+
+    let c0: vec3f = vec3f(r12) + rs;
+    var i_irid: vec3f = c0;
+
+    var cm: vec3f = rs - vec3f(t121);
+
+    cm = cm * r123;
+    let sm1: vec3f = 2.0 * iridescence_sensitivity(1.0 * opd, 1.0 * phi);
+    i_irid = i_irid + cm * sm1;
+
+    cm = cm * r123;
+    let sm2: vec3f = 2.0 * iridescence_sensitivity(2.0 * opd, 2.0 * phi);
+    i_irid = i_irid + cm * sm2;
+
+    return max(i_irid, vec3f(0.0));
+}
+
+fn getIridescenceDiffraction(cosTheta: f32, specularity: vec3f, iridescenceThickness: f32) -> vec3f {
+    return calcIridescence(1.0, cosTheta, specularity, iridescenceThickness);
+}
+`;

src/scene/shader-lib/chunks-wgsl/lit/frag/pass-forward/litForwardBackend.js

@@ -30,7 +30,7 @@ fn evaluateBackend() -> FragmentOutput {
         #endif
 
         #ifdef LIT_IRIDESCENCE
-            var iridescenceFresnel: vec3f = getIridescence(saturate3(dot(dViewDirW, litArgs_worldNormal)), litArgs_specularity, litArgs_iridescence_thickness);
+            var iridescenceFresnel: vec3f = getIridescenceDiffraction(saturate(dot(dViewDirW, litArgs_worldNormal)), litArgs_specularity, litArgs_iridescence_thickness);
         #endif
     #endif
 

src/scene/shader-lib/chunks/lit/frag/iridescenceDiffraction.js

@@ -1,10 +1,6 @@
 export default /* glsl */`
 uniform float material_iridescenceRefractionIndex;
 
-#ifndef PI
-#define PI 3.14159265
-#endif
-
 float iridescence_iorToFresnel(float transmittedIor, float incidentIor) {
     return pow((transmittedIor - incidentIor) / (transmittedIor + incidentIor), 2.0);
 }
@@ -19,6 +15,7 @@ vec3 iridescence_fresnelToIor(vec3 f0) {
 }
 
 vec3 iridescence_sensitivity(float opd, vec3 shift) {
+    float PI = 3.141592653589793;
     float phase = 2.0 * PI * opd * 1.0e-9;
     const vec3 val = vec3(5.4856e-13, 4.4201e-13, 5.2481e-13);
     const vec3 pos = vec3(1.6810e+06, 1.7953e+06, 2.2084e+06);
@@ -52,6 +49,7 @@ vec3 iridescence_fresnel(float cosTheta, vec3 f0) {
 }
 
 vec3 calcIridescence(float outsideIor, float cosTheta, vec3 base_f0, float iridescenceThickness) {
+    float PI = 3.141592653589793;
 
     float iridescenceIor = mix(outsideIor, material_iridescenceRefractionIndex, smoothstep(0.0, 0.03, iridescenceThickness));
     float sinTheta2Sq = pow(outsideIor / iridescenceIor, 2.0) * (1.0 - pow(cosTheta, 2.0));