WGSL version of an internal floatAsUintPS shader chunk (#7631)

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

Author: mvaligursky

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

@@ -38,7 +38,7 @@ import envAtlasPS from './common/frag/envAtlas.js';
 import envProcPS from './common/frag/envProc.js';
 import falloffInvSquaredPS from './lit/frag/falloffInvSquared.js';
 import falloffLinearPS from './lit/frag/falloffLinear.js';
-// import floatAsUintPS from './common/frag/float-as-uint.js';
+import floatAsUintPS from './common/frag/float-as-uint.js';
 import fogPS from './common/frag/fog.js';
 import fresnelSchlickPS from './lit/frag/fresnelSchlick.js';
 import fullscreenQuadVS from './common/vert/fullscreenQuad.js';
@@ -250,7 +250,7 @@ const shaderChunksWGSL = {
     envProcPS,
     falloffInvSquaredPS,
     falloffLinearPS,
-    // floatAsUintPS,
+    floatAsUintPS,
     fogPS,
     fresnelSchlickPS,
     fullscreenQuadVS,

src/scene/shader-lib/chunks-wgsl/common/frag/float-as-uint.js

@@ -0,0 +1,42 @@
+// Chunk that allows us to store all 32bits of float in a single RGBA8 texture without any loss of
+// precision. The float value is encoded to RGBA8 and decoded back to float. Used as a fallback
+// for platforms that do not support float textures but need to render to a float texture (without
+// filtering)
+export default /* wgsl */`
+
+#ifndef FLOAT_AS_UINT
+#define FLOAT_AS_UINT
+
+// encode float value to RGBA8 representation (0.0-1.0 range)
+fn float2uint(value: f32) -> vec4f {
+    let intBits = bitcast<u32>(value);
+    return vec4f(
+        f32((intBits >> 24u) & 0xffu),
+        f32((intBits >> 16u) & 0xffu),
+        f32((intBits >> 8u) & 0xffu),
+        f32(intBits & 0xffu)
+    ) / 255.0;
+}
+
+// decode RGBA8 value to float
+fn uint2float(value: vec4f) -> f32 {
+    let rgba_u32 = vec4<u32>(value * 255.0);
+    let intBits: u32 =
+        (rgba_u32.r << 24u) |
+        (rgba_u32.g << 16u) |
+        (rgba_u32.b << 8u)  |
+         rgba_u32.a;
+    return bitcast<f32>(intBits);
+}
+
+// store a single float value in vec4, assuming either RGBA8 or float renderable texture
+fn float2vec4(value: f32) -> vec4f {
+    #if defined(CAPS_TEXTURE_FLOAT_RENDERABLE)
+        return vec4f(value, 1.0, 1.0, 1.0);
+    #else
+        return float2uint(value);
+    #endif
+}
+
+#endif // FLOAT_AS_UINT
+`;

src/scene/shader-lib/chunks-wgsl/lit/vert/litMain.js

@@ -99,7 +99,7 @@ fn vertexMain(input : VertexInput) -> VertexOutput {
 
     #ifdef LINEAR_DEPTH
         // linear depth from the worldPosition, see getLinearDepth
-        output.vLinearDepth = -(matrix_view * vec4f(vPositionW, 1.0)).z;
+        output.vLinearDepth = -(uniform.matrix_view * vec4f(output.vPositionW, 1.0)).z;
     #endif
 
     #ifdef MSDF