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Cycles: Fix rays parallel to the surface in the triangle refine and MultiGGX code 

In the triangle intersection refinement code, rays that are parallel to the triangle caused a divide by zero.
These rays might initially hit the triangle due to the watertight intersection test, but are very rare - therefore, just skipping the refinement for them works fine.

Also, a few remaining issues in the MultiGGX code are fixed that were caused by rays parallel to the surface (which happened more often there due to smooth shading).
This commit is contained in:
Lukas Stockner 2016-07-25 16:02:25 +02:00
parent 83ae0a0e06
commit d9cc3ea2c6
2 changed files with 28 additions and 11 deletions
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13
intern/cycles/kernel/closure/bsdf_microfacet_multi.h
View File

@ -42,7 +42,7 @@ ccl_device_inline float D_ggx_aniso(const float3 wm, const float2 alpha)
/* Sample slope distribution (based on page 14 of the supplemental implementation). */
ccl_device_inline float2 mf_sampleP22_11(const float cosI, const float2 randU)
{
if(cosI > 0.9999f) {
if(cosI > 0.9999f || cosI < 1e-6f) {
const float r = sqrtf(randU.x / (1.0f - randU.x));
const float phi = M_2PI_F * randU.y;
return make_float2(r*cosf(phi), r*sinf(phi));
@ -117,7 +117,7 @@ ccl_device_inline float3 mf_eval_phase_glossy(const float3 w, const float lambda
if(dotW_WH < 0.0f)
return make_float3(0.0f, 0.0f, 0.0f);
float phase = max(0.0f, dotW_WH) * 0.25f / (pArea * dotW_WH);
float phase = max(0.0f, dotW_WH) * 0.25f / max(pArea * dotW_WH, 1e-7f);
if(alpha.x == alpha.y)
phase *= D_ggx(wh, alpha.x);
else
@ -200,9 +200,9 @@ ccl_device_inline float mf_lambda(const float3 w, const float2 alpha)
if(w.z > 0.9999f)
return 0.0f;
else if(w.z < -0.9999f)
return -1.0f;
return -0.9999f;
const float inv_wz2 = 1.0f / (w.z*w.z);
const float inv_wz2 = 1.0f / max(w.z*w.z, 1e-7f);
const float2 wa = make_float2(w.x, w.y)*alpha;
float v = sqrtf(1.0f + dot(wa, wa) * inv_wz2);
if(w.z <= 0.0f)
@ -271,7 +271,10 @@ ccl_device_inline float mf_ggx_albedo(float r)
ccl_device_inline float mf_ggx_pdf(const float3 wi, const float3 wo, const float alpha)
{
return 0.25f * D_ggx(normalize(wi+wo), alpha) / ((1.0f + mf_lambda(wi, make_float2(alpha, alpha))) * wi.z) + (1.0f - mf_ggx_albedo(alpha)) * wo.z;
float D = D_ggx(normalize(wi+wo), alpha);
float lambda = mf_lambda(wi, make_float2(alpha, alpha));
float albedo = mf_ggx_albedo(alpha);
return 0.25f * D / max((1.0f + lambda) * wi.z, 1e-7f) + (1.0f - albedo) * wo.z;
}
ccl_device_inline float mf_ggx_aniso_pdf(const float3 wi, const float3 wo, const float2 alpha)

26
intern/cycles/kernel/geom/geom_triangle_intersect.h
View File

@ -342,9 +342,16 @@ ccl_device_inline float3 triangle_refine(KernelGlobals *kg,
float3 tvec = make_float3(P.x - tri_c.x, P.y - tri_c.y, P.z - tri_c.z);
float3 qvec = cross(tvec, edge1);
float3 pvec = cross(D, edge2);
float rt = dot(edge2, qvec) / dot(edge1, pvec);
P = P + D*rt;
float det = dot(edge1, pvec);
if(det != 0.0f) {
/* If determinant is zero it means ray lies in the plane of
* the triangle. It is possible in theory due to watertight
* nature of triangle intersection. For suc hcases we simply
* don't refine intersection hoping it'll go all fine.
*/
float rt = dot(edge2, qvec) / det;
P = P + D*rt;
}
if(isect->object != OBJECT_NONE) {
# ifdef __OBJECT_MOTION__
@ -400,9 +407,16 @@ ccl_device_inline float3 triangle_refine_subsurface(KernelGlobals *kg,
float3 tvec = make_float3(P.x - tri_c.x, P.y - tri_c.y, P.z - tri_c.z);
float3 qvec = cross(tvec, edge1);
float3 pvec = cross(D, edge2);
float rt = dot(edge2, qvec) / dot(edge1, pvec);
P = P + D*rt;
float det = dot(edge1, pvec);
if(det != 0.0f) {
/* If determinant is zero it means ray lies in the plane of
* the triangle. It is possible in theory due to watertight
* nature of triangle intersection. For such cases we simply
* don't refine intersection hoping it'll go all fine.
*/
float rt = dot(edge2, qvec) / det;
P = P + D*rt;
}
#endif /* __INTERSECTION_REFINE__ */
if(isect->object != OBJECT_NONE) {