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Cycles: Fix three numerical issues in the fresnel, normal map and Beckmann code

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- In fresnel_dielectric, the differentials calculation sometimes divided by zero.
- When the normal map was (0.5, 0.5, 0.5), the code would try to normalize a zero vector. Now, it just uses the regular normal as a fallback.
- The approximate error function used in Beckmann sampling sometimes overflowed to inf while calculating r^16. The final value is 1 - 1/r^16, however,
  so now it just returns 1 if the computation would overflow otherwise.
This commit is contained in:
Lukas Stockner
2016-07-16 20:48:12 +02:00
parent 5ba78d76d4
commit d9281a6332
3 changed files with 11 additions and 4 deletions
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2
intern/cycles/kernel/closure/bsdf_util.h
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@@ -80,7 +80,7 @@ ccl_device float fresnel_dielectric(
return 1; // total internal reflection return 1; // total internal reflection
} }
else { else {
float dnp = sqrtf(arg); float dnp = max(sqrtf(arg), 1e-7f);
float nK = (neta * cos)- dnp; float nK = (neta * cos)- dnp;
*T = -(neta * I)+(nK * Nn); *T = -(neta * I)+(nK * Nn);
#ifdef __RAY_DIFFERENTIALS__ #ifdef __RAY_DIFFERENTIALS__

10
intern/cycles/kernel/svm/svm_tex_coord.h
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@@ -312,7 +312,7 @@ ccl_device void svm_node_normal_map(KernelGlobals *kg, ShaderData *sd, float *st
/* apply normal map */ /* apply normal map */
float3 B = sign * cross(normal, tangent); float3 B = sign * cross(normal, tangent);
N = normalize(color.x * tangent + color.y * B + color.z * normal); N = safe_normalize(color.x * tangent + color.y * B + color.z * normal);
/* transform to world space */ /* transform to world space */
object_normal_transform(kg, sd, &N); object_normal_transform(kg, sd, &N);
@@ -330,14 +330,18 @@ ccl_device void svm_node_normal_map(KernelGlobals *kg, ShaderData *sd, float *st
if(space == NODE_NORMAL_MAP_OBJECT || space == NODE_NORMAL_MAP_BLENDER_OBJECT) if(space == NODE_NORMAL_MAP_OBJECT || space == NODE_NORMAL_MAP_BLENDER_OBJECT)
object_normal_transform(kg, sd, &N); object_normal_transform(kg, sd, &N);
else else
N = normalize(N); N = safe_normalize(N);
} }
float strength = stack_load_float(stack, strength_offset); float strength = stack_load_float(stack, strength_offset);
if(strength != 1.0f) { if(strength != 1.0f) {
strength = max(strength, 0.0f); strength = max(strength, 0.0f);
N = normalize(ccl_fetch(sd, N) + (N - ccl_fetch(sd, N))*strength); N = safe_normalize(ccl_fetch(sd, N) + (N - ccl_fetch(sd, N))*strength);
}
if(N == make_float3(0.0f, 0.0f, 0.0f)) {
N = ccl_fetch(sd, N);
} }
stack_store_float3(stack, normal_offset, N); stack_store_float3(stack, normal_offset, N);

3
intern/cycles/util/util_math_fast.h
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@@ -547,6 +547,9 @@ ccl_device_inline float fast_erff(float x)
const float a5 = 0.0002765672f; const float a5 = 0.0002765672f;
const float a6 = 0.0000430638f; const float a6 = 0.0000430638f;
const float a = fabsf(x); const float a = fabsf(x);
if(a >= 12.3f) {
return copysignf(1.0f, x);
}
const float b = 1.0f - (1.0f - a); /* Crush denormals. */ const float b = 1.0f - (1.0f - a); /* Crush denormals. */
const float r = madd(madd(madd(madd(madd(madd(a6, b, a5), b, a4), b, a3), b, a2), b, a1), b, 1.0f); const float r = madd(madd(madd(madd(madd(madd(a6, b, a5), b, a4), b, a3), b, a2), b, a1), b, 1.0f);
const float s = r * r; /* ^2 */ const float s = r * r; /* ^2 */