[Bf-blender-cvs] [fc4f45a0a40] cycles-x: Fix T91425: VDB shadow rendering incorrect in some cases

[Brecht Van Lommel]

Commit: fc4f45a0a40583ab65a83c3e291e67bd851afafb
Author: Brecht Van Lommel
Date:   Mon Sep 20 14:24:31 2021 +0200
Branches: cycles-x
https://developer.blender.org/rBfc4f45a0a40583ab65a83c3e291e67bd851afafb

Fix T91425: VDB shadow rendering incorrect in some cases

===================================================================

M	intern/cycles/bvh/bvh_embree.cpp
M	intern/cycles/kernel/bvh/bvh_shadow_all.h

===================================================================

diff --git a/intern/cycles/bvh/bvh_embree.cpp b/intern/cycles/bvh/bvh_embree.cpp
index 03226dcbc77..96852510b63 100644
--- a/intern/cycles/bvh/bvh_embree.cpp
+++ b/intern/cycles/bvh/bvh_embree.cpp
@@ -104,21 +104,26 @@ static void rtc_filter_occluded_func(const RTCFilterFunctionNArguments *args)
         /* If maximum number of hits was reached, replace the intersection with the
          * highest distance. We want to find the N closest intersections. */
         int isect_index = num_recorded_hits;
-        if (isect_index >= ctx->max_hits) {
+        if (num_recorded_hits + 1 >= ctx->max_hits) {
           float max_t = ctx->isect_s[0].t;
-          isect_index = 0;
+          int max_recorded_hit = 0;
 
           for (int i = 1; i < num_recorded_hits; ++i) {
             if (ctx->isect_s[i].t > max_t) {
-              isect_index = i;
+              max_recorded_hit = i;
               max_t = ctx->isect_s[i].t;
             }
           }
 
-          /* TODO: is there some way we can tell Embree to stop intersecting beyond
+          if (num_recorded_hits >= ctx->max_hits) {
+            isect_index = max_recorded_hit;
+          }
+
+          /* Limit the ray distance and stop counting hits beyond this.
+           * TODO: is there some way we can tell Embree to stop intersecting beyond
            * this distance when max number of hits is reached?. Or maybe it will
            * become irrelevant if we make max_hits a very high number on the CPU. */
-          ctx->max_t = min(current_isect.t, max_t);
+          ctx->max_t = max(current_isect.t, max_t);
         }
 
         ctx->isect_s[isect_index] = current_isect;
diff --git a/intern/cycles/kernel/bvh/bvh_shadow_all.h b/intern/cycles/kernel/bvh/bvh_shadow_all.h
index d2e3be78d4e..0ae36fccf9b 100644
--- a/intern/cycles/kernel/bvh/bvh_shadow_all.h
+++ b/intern/cycles/kernel/bvh/bvh_shadow_all.h
@@ -221,12 +221,8 @@ ccl_device_inline
 
                 isect = isect_array + max_recorded_hit;
 
-                /* If we already found more hits than we record, we can limit the
-                 * ray distance and stop counting hits beyond this, as we are sure to
-                 * need to another ray-trace call. */
-                if (*num_hits > max_hits) {
-                  isect_t = max_recorded_t * t_world_to_instance;
-                }
+                /* Limit the ray distance and stop counting hits beyond this. */
+                isect_t = max_recorded_t * t_world_to_instance;
               }
               else {
                 /* Still have space for intersection, use next hit. */