gi: protections against division by zero

src/gi/shaders/common.glsl

@@ -27,6 +27,25 @@ const float PI = 3.1415926535897932384626433832795;
 #define AOV_ID_DEBUG_SIDEDNESS 10
 #define AOV_ID_OBJECTID 11
 
+float safe_div(float f1, float f2)
+{
+    return (f2 == 0.0) ? 0.0 : (f1 / f2);
+}
+
+vec3 safe_div(vec3 v, float f)
+{
+    return (f == 0.0) ? vec3(0.0) : (v / f);
+}
+
+vec3 safe_div(vec3 v1, vec3 v2)
+{
+    return vec3(
+        (v2.x == 0.0) ? 0.0 : (v1.x / v2.x),
+        (v2.y == 0.0) ? 0.0 : (v1.y / v2.y),
+        (v2.z == 0.0) ? 0.0 : (v1.z / v2.z)
+    );
+}
+
 vec4 uvec4AsVec4(uvec4 v)
 {
     v >>= 9;
@@ -238,7 +257,7 @@ vec2 sample_disk(vec2 xi, vec2 radius)
     else
     {
         r = radius * b;
-        phi = (PI / 2) - (PI / 4) * (a / b);
+        phi = (PI / 2) - (PI / 4) * safe_div(a, b);
     }
 
     return r * vec2(cos(phi), sin(phi));

src/gi/shaders/rp_main.chit

@@ -36,12 +36,12 @@ void sampleLight(vec4 k4, vec3 surfacePos, out vec3 dirToLight, out float dist,
         vec3 samplePos = light.pos + sample_sphere(k4.zw, light.radiusXYZ);
         vec3 dir = samplePos - surfacePos;
         dist = length(dir);
-        dirToLight = dir / dist;
+        dirToLight = safe_div(dir, dist);
 
         // https://graphics.cg.uni-saarland.de/courses/ris-2021/slides/03_ProbabilityTheory_MonteCarlo.pdf s.35
         vec3 lightNormal = normalize(samplePos - light.pos);
         float cosTheta = max(0.0, dot(-dirToLight, lightNormal));
-        invPdf = ((light.area > 0.0) ? (light.area * cosTheta) : 1.0) / (dist * dist);
+        invPdf = safe_div((light.area > 0.0) ? (light.area * cosTheta) : 1.0, dist * dist);
 
         power = light.baseEmission * PC.lightIntensityMultiplier;
         diffuseSpecularPacked = light.diffuseSpecularPacked;
@@ -88,12 +88,12 @@ void sampleLight(vec4 k4, vec3 surfacePos, out vec3 dirToLight, out float dist,
 
         vec3 dir = samplePos - surfacePos;
         dist = length(dir);
-        dirToLight = dir / dist;
+        dirToLight = safe_div(dir, dist);
 
         vec3 lightNormal = cross(t1, t0); // light forward/default dir is -Z (like UsdLux)
         float cosTheta = max(0.0, dot(-dirToLight, lightNormal));
         float area = light.width * light.height;
-        invPdf = ((area > 0.0) ? (area * cosTheta) : 1.0) / (dist * dist);
+        invPdf = safe_div((area > 0.0) ? (area * cosTheta) : 1.0, dist * dist);
 
         power = light.baseEmission * PC.lightIntensityMultiplier;
         diffuseSpecularPacked = light.diffuseSpecularPacked;
@@ -115,12 +115,12 @@ void sampleLight(vec4 k4, vec3 surfacePos, out vec3 dirToLight, out float dist,
 
         vec3 dir = samplePos - surfacePos;
         dist = length(dir);
-        dirToLight = dir / dist;
+        dirToLight = safe_div(dir, dist);
 
         vec3 lightNormal = cross(t1, t0); // light forward/default dir is -Z (like UsdLux)
         float cosTheta = max(0.0, dot(-dirToLight, lightNormal));
         float area = radiusXY.x * radiusXY.y * PI;
-        invPdf = ((area > 0.0) ? (area * cosTheta) : 1.0) / (dist * dist);
+        invPdf = safe_div((area > 0.0) ? (area * cosTheta) : 1.0, dist * dist);
 
         power = light.baseEmission * PC.lightIntensityMultiplier;
         diffuseSpecularPacked = light.diffuseSpecularPacked;

src/gi/shaders/rp_main.rgen

@@ -53,7 +53,7 @@ vec3 evaluate_sample(vec3 ray_origin,
 
     // Correct clip plane curving by getting the hypothenuse length (our current ray)
     // from the adjacent edge (the forward vector) the angle between both.
-    float cosConeAngle = dot(ray_dir, PC.cameraForward);
+    float cosConeAngle = max(1e-5, dot(ray_dir, PC.cameraForward));
     vec2 clipRange = unpackHalf2x16(PC.clipRangePacked) / cosConeAngle;
 
     // Path trace
@@ -128,10 +128,10 @@ vec3 evaluate_sample(vec3 ray_origin,
 
             vec3 shadowRayOrigin = rayPayload.ray_origin; // actually not correct, but we compensate with tMin
             float lightDist = length(rayPayload.neeToLight);
-            vec3 shadowRayDir = rayPayload.neeToLight / lightDist;
+            vec3 shadowRayDir = safe_div(rayPayload.neeToLight, lightDist); // according to spec, must not contain NaNs
 
             // NV best practices recommends unconditional dispatch with tMin = tMax = 0.0
-            bool traceRay = luminance(rayPayload.neeContrib) > 1e-6 && lightDist > 0.0;
+            bool traceRay = luminance(rayPayload.neeContrib) > 1e-6 && lightDist > 1e-9;
             uint rayFlags = gl_RayFlagsTerminateOnFirstHitEXT | gl_RayFlagsSkipClosestHitShaderEXT;
             float tMin = traceRay ? 0.01 : 0.0; // FIXME: investigate resulting artifacts
             float tMax = traceRay ? lightDist : 0.0;