intern/cycles/bvh/bvh.h

@@ -65,7 +65,7 @@ class BVH {
   BVHParams params;
   vector<Geometry *> geometry;
   vector<Object *> objects;
-
+  bool built;
   static BVH *create(const BVHParams &params,
                      const vector<Geometry *> &geometry,
                      const vector<Object *> &objects,

intern/cycles/bvh/bvh2.h

@@ -10,6 +10,7 @@
 
 #include "util/types.h"
 #include "util/vector.h"
+#include "util/thread.h"
 
 CCL_NAMESPACE_BEGIN
 
@@ -32,6 +33,11 @@ struct BVHStackEntry {
  */
 class BVH2 : public BVH {
  public:
+    /* The BVH2 needs to be build only once these
+     are used to ensure that it the case.       */
+  thread_mutex build_mutex;
+  thread_condition_variable build_cv;
+  
   void build(Progress &progress, Stats *stats);
   void refit(Progress &progress);
 

intern/cycles/device/device.cpp

@@ -52,13 +52,39 @@ Device::~Device() noexcept(false)
 void Device::build_bvh(BVH *bvh, DeviceScene *dscene, Progress &progress, bool refit)
 {
   assert(bvh->params.bvh_layout == BVH_LAYOUT_BVH2);
-
   BVH2 *const bvh2 = static_cast<BVH2 *>(bvh);
-  if (refit) {
-    bvh2->refit(progress);
+  thread_scoped_lock build_lock(bvh2->build_mutex, std::try_to_lock);
+  if (build_lock) {
+    /* Has the BVH already been built */
+    if (!bvh->built) {
+      /* Build the BVH */
+      VLOG_INFO << "Performing BVH2 build.";
+
+      if (refit) {
+        bvh2->refit(progress);
+      }
+      else {
+        bvh2->build(progress, &stats);
+      }
+      bvh->built = true;
+      VLOG_INFO << "done building BVH2";
+    }
+    else {
+      VLOG_INFO << "BVH2 Already built";
+    }
+    bvh2->build_cv.notify_all();
   }
   else {
-    bvh2->build(progress, &stats);
+    /* Only need to wait for the top level BVH otherwise
+       this thread can skip on the the next object */
+    if (bvh2->params.top_level) {
+      /* wait for BVH build to complete before proceeding */
+      VLOG_INFO << "Waiting  on BVH2 build.";
+      bvh2->build_cv.wait(build_lock);
+      VLOG_INFO << "done waiting on BVH2 build";
+    } else {
+      VLOG_INFO << "Skipping BVH2 build.";
+    }
   }
 }
 

intern/cycles/scene/geometry.cpp

@@ -1222,7 +1222,7 @@ void GeometryManager::deviceDataXferAndBVHUpdate(int idx,
   // the correct data
   device_update_host_pointers(sub_device, dscene, sub_dscene, &sizes);
 
-  // Upload geometry and attribute buffers to the device
+  /* Upload geometry and attribute buffers to the device */
   {
     scoped_callback_timer timer([scene, idx](double time) {
       if (scene->update_stats) {
@@ -1250,6 +1250,7 @@ void GeometryManager::deviceDataXferAndBVHUpdate(int idx,
       }
     });
     size_t i = 0;
+    /* Build the Object BVHs */
     foreach (Geometry *geom, scene->geometry) {
       if (geom->is_modified() || geom->need_update_bvh_for_offset) {
         geom->compute_bvh(sub_device, sub_dscene, &scene->params, &progress, i, num_bvh);
@@ -1266,6 +1267,7 @@ void GeometryManager::deviceDataXferAndBVHUpdate(int idx,
         scene->scene_bvh_times[idx] = time;
       }
     });
+    /* Build the scene BVH */
     device_update_bvh(sub_device, sub_dscene, scene, can_refit, 1, 1, progress);
     device_update_bvh2(sub_device, sub_dscene, scene, progress);
   }
@@ -1485,6 +1487,7 @@ void GeometryManager::device_update(Device *device,
   }
   {
     size_t num_scenes = scene->dscenes.size();
+    VLOG_INFO << "Rendering using " << num_scenes << " devices";
     // Parallel upload the geometry data to the devices and
     // calculate or refit the BVHs
     parallel_for(

intern/cycles/scene/geometry_additions.cpp

@@ -933,7 +933,8 @@ bool GeometryManager::device_update_bvh_preprocess(Device *device,
   if (!scene->bvh) {
     bvh = scene->bvh = BVH::create(bparams, scene->geometry, scene->objects, device);
   }
-
+  /* Mark BVH as having not been built yet */
+  bvh->built = false;
   return can_refit;
 }