Fix T68290: Baked particles don't render in final frame

Particles baked into memory would never load the final frame because
of an off-by-one error calculating the particles `dietime`.

This value indicates the frame which the particle ceases to exist but
was being set to the end-frame which caused this bug as the scenes
end-frame is inclusive.

While the last frame was properly written and read from memory,
the `dietime` was set to the last frame causing all the particles to be
considered dead when calculating the cached particle system.

1 files changed, 15 insertions, 10 deletions

diff --git a/source/blender/blenkernel/intern/particle.c b/source/blender/blenkernel/intern/particle.c
index 9ea1336a95a..500596e6d42 100644
--- a/source/blender/blenkernel/intern/particle.c
+++ b/source/blender/blenkernel/intern/particle.c
@@ -1249,7 +1249,9 @@ typedef struct ParticleInterpolationData {
   PTCacheEditPoint *epoint;
   PTCacheEditKey *ekey[2];
 
-  float birthtime, dietime;
+  float birthtime;
+  /** Die on this frame, see #ParticleData.dietime for details. */
+  float dietime;
   int bspline;
 } ParticleInterpolationData;
 /**
@@ -1311,15 +1313,15 @@ static void get_pointcache_keys_for_time(Object *UNUSED(ob),
 }
 static int get_pointcache_times_for_particle(PointCache *cache,
                                              int index,
-                                             float *start,
-                                             float *end)
+                                             float *r_start,
+                                             float *r_dietime)
 {
   PTCacheMem *pm;
   int ret = 0;
 
   for (pm = cache->mem_cache.first; pm; pm = pm->next) {
     if (BKE_ptcache_mem_index_find(pm, index) >= 0) {
-      *start = pm->frame;
+      *r_start = pm->frame;
       ret++;
       break;
     }
@@ -1327,7 +1329,8 @@ static int get_pointcache_times_for_particle(PointCache *cache,
 
   for (pm = cache->mem_cache.last; pm; pm = pm->prev) {
     if (BKE_ptcache_mem_index_find(pm, index) >= 0) {
-      *end = pm->frame;
+      /* Die *after* the last available frame. */
+      *r_dietime = pm->frame + 1;
       ret++;
       break;
     }
@@ -1343,7 +1346,9 @@ float psys_get_dietime_from_cache(PointCache *cache, int index)
 
   for (pm = cache->mem_cache.last; pm; pm = pm->prev) {
     if (BKE_ptcache_mem_index_find(pm, index) >= 0) {
-      return (float)pm->frame;
+      /* Die *after* the last available frame. */
+      dietime = pm->frame + 1;
+      break;
     }
   }
 
@@ -1374,14 +1379,14 @@ static void init_particle_interpolation(Object *ob,
     pind->dietime = (key + pa->totkey - 1)->time;
   }
   else if (pind->cache) {
-    float start = 0.0f, end = 0.0f;
+    float start = 0.0f, dietime = 0.0f;
     get_pointcache_keys_for_time(ob, pind->cache, &pind->pm, -1, 0.0f, NULL, NULL);
     pind->birthtime = pa ? pa->time : pind->cache->startframe;
-    pind->dietime = pa ? pa->dietime : pind->cache->endframe;
+    pind->dietime = pa ? pa->dietime : (pind->cache->endframe + 1);
 
-    if (get_pointcache_times_for_particle(pind->cache, pa - psys->particles, &start, &end)) {
+    if (get_pointcache_times_for_particle(pind->cache, pa - psys->particles, &start, &dietime)) {
       pind->birthtime = MAX2(pind->birthtime, start);
-      pind->dietime = MIN2(pind->dietime, end);
+      pind->dietime = MIN2(pind->dietime, dietime + 1);
     }
   }
   else {