[#81] Optimize reflections by using noise to hide lower sample count

projects/voxelization/resources/shaders/shader.frag

@@ -50,6 +50,12 @@ float roughnessToConeAngle(float r){
     return mix(degreeToRadian(20), degreeToRadian(90), r);
 }
 
+// from: "Next Generation Post Processing in Call Of Duty Advanced Warfare" slide page 123
+float interleavedGradientNoise(vec2 uv){
+    vec3 magic = vec3(0.06711056, 0.00583715, 62.9829189);
+    return fract(magic.z * fract(dot(uv, magic.xy)));
+}
+
 void main()	{
 
     vec3 albedoTexel    = texture(sampler2D(albedoTexture, textureSampler), passUV).rgb;
@@ -95,6 +101,7 @@ void main()	{
     vec3 R                      = reflect(-V, N);
     float reflectionConeAngle   = degreeToRadian(roughnessToConeAngle(r));
     vec3 offsetTraceStart       = passPos + N_geo * 0.1f;
+    offsetTraceStart            += R * interleavedGradientNoise(gl_FragCoord.xy) * 0.5;
     vec3 specularTrace          = voxelConeTrace(R, offsetTraceStart, reflectionConeAngle, voxelTexture, voxelSampler, voxelInfo);
     specularTrace               *= clamp(dot(N, R), 0, 1);
     vec3 reflectionBRDF         = cookTorrance(f0, r, N, V, R);

projects/voxelization/resources/shaders/voxel.inc

@@ -130,7 +130,7 @@ vec3 voxelConeTrace(vec3 direction, vec3 startPosition, float coneAngleRadian, t
     
     float coneAngleHalf = coneAngleRadian * 0.5f;
     
-    int maxSamples = 128;
+    int maxSamples = 16;
     for(int i = 0; i < maxSamples; i++){
         
         vec3 samplePos      = startPosition + d * direction;
@@ -149,7 +149,7 @@ vec3 voxelConeTrace(vec3 direction, vec3 startPosition, float coneAngleRadian, t
         color               += (1 - a) * voxelSample.rgb;
         a                   += (1 - a) * voxelSample.a;
         
-        float minStepSize   = 0.15;
+        float minStepSize   = 0.5f;
         d                   += max(coneDiameter, minStepSize);
         samplePos           = startPosition + d * direction;
         sampleUV            = worldToVoxelCoordinates(samplePos, voxelInfo);