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Fix T74939: Random Walk subsurface appearance in OptiX does not match other engines 

Random Walk subsurface scattering did look different with OptiX because transmittance is
calculated based on the hit distance, but the OptiX implementation of `scene_intersect_local`
would return the distance in world space, while the Cycles BVH version returns it in object
space. This fixes the problem by simply skipping the object->world transforms in all the
places using the result of `scene_intersect_local` with OptiX.

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D7232
This commit is contained in:
Patrick Mours 2020-03-25 18:30:39 +01:00
parent 08b9b95147
commit bd2b1a67a7
Notes: blender-bot 2023-02-14 03:44:41 +01:00 
Referenced by issue #74939, Random Walk subsurface appearance in OptiX does not match other engines
3 changed files with 32 additions and 17 deletions
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23
intern/cycles/kernel/geom/geom_motion_triangle_intersect.h
View File

@ -103,17 +103,21 @@ ccl_device_inline
const Ray *ray,
float3 verts[3])
{
# ifdef __KERNEL_OPTIX__
/* isect->t is always in world space with OptiX. */
return motion_triangle_refine(kg, sd, isect, ray, verts);
# else
float3 P = ray->P;
float3 D = ray->D;
float t = isect->t;
# ifdef __INTERSECTION_REFINE__
# ifdef __INTERSECTION_REFINE__
if (isect->object != OBJECT_NONE) {
# ifdef __OBJECT_MOTION__
# ifdef __OBJECT_MOTION__
Transform tfm = sd->ob_itfm;
# else
# else
Transform tfm = object_fetch_transform(kg, isect->object, OBJECT_INVERSE_TRANSFORM);
# endif
# endif
P = transform_point(&tfm, P);
D = transform_direction(&tfm, D);
@ -135,19 +139,20 @@ ccl_device_inline
P = P + D * rt;
if (isect->object != OBJECT_NONE) {
# ifdef __OBJECT_MOTION__
# ifdef __OBJECT_MOTION__
Transform tfm = sd->ob_tfm;
# else
# else
Transform tfm = object_fetch_transform(kg, isect->object, OBJECT_TRANSFORM);
# endif
# endif
P = transform_point(&tfm, P);
}
return P;
# else /* __INTERSECTION_REFINE__ */
# else /* __INTERSECTION_REFINE__ */
return P + D * t;
# endif /* __INTERSECTION_REFINE__ */
# endif /* __INTERSECTION_REFINE__ */
# endif
}
#endif /* __BVH_LOCAL__ */

21
intern/cycles/kernel/geom/geom_triangle_intersect.h
View File

@ -690,16 +690,20 @@ ccl_device_inline float3 triangle_refine_local(KernelGlobals *kg,
const Intersection *isect,
const Ray *ray)
{
#ifdef __KERNEL_OPTIX__
/* isect->t is always in world space with OptiX. */
return triangle_refine(kg, sd, isect, ray);
#else
float3 P = ray->P;
float3 D = ray->D;
float t = isect->t;
if (isect->object != OBJECT_NONE) {
#ifdef __OBJECT_MOTION__
# ifdef __OBJECT_MOTION__
Transform tfm = sd->ob_itfm;
#else
# else
Transform tfm = object_fetch_transform(kg, isect->object, OBJECT_INVERSE_TRANSFORM);
#endif
# endif
P = transform_point(&tfm, P);
D = transform_direction(&tfm, D);
@ -708,7 +712,7 @@ ccl_device_inline float3 triangle_refine_local(KernelGlobals *kg,
P = P + D * t;
#ifdef __INTERSECTION_REFINE__
# ifdef __INTERSECTION_REFINE__
const uint tri_vindex = kernel_tex_fetch(__prim_tri_index, isect->prim);
const float4 tri_a = kernel_tex_fetch(__prim_tri_verts, tri_vindex + 0),
tri_b = kernel_tex_fetch(__prim_tri_verts, tri_vindex + 1),
@ -728,19 +732,20 @@ ccl_device_inline float3 triangle_refine_local(KernelGlobals *kg,
float rt = dot(edge2, qvec) / det;
P = P + D * rt;
}
#endif /* __INTERSECTION_REFINE__ */
# endif /* __INTERSECTION_REFINE__ */
if (isect->object != OBJECT_NONE) {
#ifdef __OBJECT_MOTION__
# ifdef __OBJECT_MOTION__
Transform tfm = sd->ob_tfm;
#else
# else
Transform tfm = object_fetch_transform(kg, isect->object, OBJECT_TRANSFORM);
#endif
# endif
P = transform_point(&tfm, P);
}
return P;
#endif
}
CCL_NAMESPACE_END

5
intern/cycles/kernel/kernel_subsurface.h
View File

@ -428,12 +428,17 @@ ccl_device_noinline
hit = (ss_isect->num_hits > 0);
if (hit) {
#ifdef __KERNEL_OPTIX__
/* t is always in world space with OptiX. */
t = ss_isect->hits[0].t;
#else
/* Compute world space distance to surface hit. */
float3 D = ray->D;
object_inverse_dir_transform(kg, sd, &D);
D = normalize(D) * ss_isect->hits[0].t;
object_dir_transform(kg, sd, &D);
t = len(D);
#endif
}
/* Advance to new scatter location. */