From 9946cca14676bf07b3c7c103e99033fe1e4e423e Mon Sep 17 00:00:00 2001 From: Sergey Sharybin Date: Fri, 15 Jul 2016 14:55:37 +0200 Subject: [PATCH] Fix T48860: Cycles SSS artifacts with spatially split BVH The issue was caused by SSS intersection code gathering all intersections without check for duplicated ones. This caused situations when same intersection will be recorded twice in the case if triangle is shared by several BVH nodes. Usually this is handled by checking intersection distance after sorting intersections (in shadow_blocked for example) but for SSS we don't do such sorting and using number of intersections to calculate various things. Didn't find anything smarter than to check intersection distance in triangle_intersect_subsurface(). This solves render artifacts in the cost of 1.5% slowdown of extreme case rendering (SSS object filling in whole FullHD screen). Reviewers: brecht Reviewed By: brecht Differential Revision: https://developer.blender.org/D2105 --- intern/cycles/kernel/geom/geom_triangle_intersect.h | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/intern/cycles/kernel/geom/geom_triangle_intersect.h b/intern/cycles/kernel/geom/geom_triangle_intersect.h index fc081bda525..720ee6a1f5c 100644 --- a/intern/cycles/kernel/geom/geom_triangle_intersect.h +++ b/intern/cycles/kernel/geom/geom_triangle_intersect.h @@ -255,6 +255,13 @@ ccl_device_inline void triangle_intersect_subsurface( /* Normalize U, V, W, and T. */ const float inv_det = 1.0f / det; + const float t = T * inv_det; + for(int i = min(max_hits, ss_isect->num_hits); i >= 0; --i) { + if(ss_isect->hits[i].t == t) { + return; + } + } + ss_isect->num_hits++; int hit; @@ -277,7 +284,7 @@ ccl_device_inline void triangle_intersect_subsurface( isect->type = PRIMITIVE_TRIANGLE; isect->u = U * inv_det; isect->v = V * inv_det; - isect->t = T * inv_det; + isect->t = t; /* Record geometric normal. */ /* TODO(sergey): Use float4_to_float3() on just an edges. */