Cycles: enable Embree by default for CPU rendering

For GPU debugging purposes, it is still possible to render with the same BVH2
on the CPU using the Debug panel in the render properties.

Note that building Blender without Embree will now lead to significantly reduced
performance in CPU rendering, and a few of the Cycles regression tests will fail
due to small pixel differences.

Ref T73778

Depends on D8014

Maniphest Tasks: T73778

Differential Revision: https://developer.blender.org/D8015

CMakeLists.txt

@@ -370,7 +370,7 @@ option(WITH_CYCLES                  "Enable Cycles Render Engine" ON)
 option(WITH_CYCLES_STANDALONE       "Build Cycles standalone application" OFF)
 option(WITH_CYCLES_STANDALONE_GUI   "Build Cycles standalone with GUI" OFF)
 option(WITH_CYCLES_OSL              "Build Cycles with OSL support" ON)
-option(WITH_CYCLES_EMBREE           "Build Cycles with Embree support" OFF)
+option(WITH_CYCLES_EMBREE           "Build Cycles with Embree support" ON)
 option(WITH_CYCLES_CUDA_BINARIES    "Build Cycles CUDA binaries" OFF)
 option(WITH_CYCLES_CUBIN_COMPILER   "Build cubins with nvrtc based compiler instead of nvcc" OFF)
 option(WITH_CYCLES_CUDA_BUILD_SERIAL "Build cubins one after another (useful on machines with limited RAM)" OFF)

intern/cycles/blender/addon/properties.py

@@ -53,6 +53,11 @@ enum_displacement_methods = (
     ('BOTH', "Displacement and Bump", "Combination of true displacement and bump mapping for finer detail"),
 )
 
+enum_bvh_layouts = (
+    ('BVH2', "BVH2", "", 1),
+    ('EMBREE', "Embree", "", 4),
+)
+
 enum_bvh_types = (
     ('DYNAMIC_BVH', "Dynamic BVH", "Objects can be individually updated, at the cost of slower render time"),
     ('STATIC_BVH', "Static BVH", "Any object modification requires a complete BVH rebuild, but renders faster"),
@@ -612,11 +617,6 @@ class CyclesRenderSettings(bpy.types.PropertyGroup):
         items=enum_bvh_types,
         default='DYNAMIC_BVH',
     )
-    use_bvh_embree: BoolProperty(
-        name="Use Embree",
-        description="Use Embree as ray accelerator",
-        default=False,
-    )
     debug_use_spatial_splits: BoolProperty(
         name="Use Spatial Splits",
         description="Use BVH spatial splits: longer builder time, faster render",
@@ -766,6 +766,11 @@ class CyclesRenderSettings(bpy.types.PropertyGroup):
     debug_use_cpu_sse41: BoolProperty(name="SSE41", default=True)
     debug_use_cpu_sse3: BoolProperty(name="SSE3", default=True)
     debug_use_cpu_sse2: BoolProperty(name="SSE2", default=True)
+    debug_bvh_layout: EnumProperty(
+        name="BVH Layout",
+        items=enum_bvh_layouts,
+        default='EMBREE',
+    )
     debug_use_cpu_split_kernel: BoolProperty(name="Split Kernel", default=False)
 
     debug_use_cuda_adaptive_compile: BoolProperty(name="Adaptive Compile", default=False)

intern/cycles/blender/blender_sync.cpp

@@ -757,11 +757,6 @@ SceneParams BlenderSync::get_scene_params(BL::Scene &b_scene, bool background)
 
   params.bvh_layout = DebugFlags().cpu.bvh_layout;
 
-#ifdef WITH_EMBREE
-  params.bvh_layout = RNA_boolean_get(&cscene, "use_bvh_embree") ? BVH_LAYOUT_EMBREE :
-                                                                   params.bvh_layout;
-#endif
-
   params.background = background;
 
   return params;

intern/cycles/kernel/kernel_types.h

@@ -1400,7 +1400,8 @@ typedef enum KernelBVHLayout {
   BVH_LAYOUT_EMBREE = (1 << 1),
   BVH_LAYOUT_OPTIX = (1 << 2),
 
-  BVH_LAYOUT_AUTO = BVH_LAYOUT_BVH2,
+  /* Default BVH layout to use for CPU. */
+  BVH_LAYOUT_AUTO = BVH_LAYOUT_EMBREE,
   BVH_LAYOUT_ALL = (unsigned int)(~0u),
 } KernelBVHLayout;