Cycles: Added Embree as BVH option for CPU renders.

Note that this is turned off by default and must be enabled at build time with the CMake WITH_CYCLES_EMBREE flag.
Embree must be built as a static library with ray masking turned on, the `make deps` scripts have been updated accordingly.
There, Embree is off by default too and must be enabled with the WITH_EMBREE flag.

Using Embree allows for much faster rendering of deformation motion blur while reducing the memory footprint.

TODO: GPU implementation, deduplication of data, leveraging more of Embrees features (e.g. tessellation cache).

Differential Revision: https://developer.blender.org/D3682

2 files changed, 22 insertions, 8 deletions

diff --git a/intern/cycles/kernel/geom/geom_curve_intersect.h b/intern/cycles/kernel/geom/geom_curve_intersect.h
index 4cfbe21685c..5901429918c 100644
--- a/intern/cycles/kernel/geom/geom_curve_intersect.h
+++ b/intern/cycles/kernel/geom/geom_curve_intersect.h
@@ -817,16 +817,24 @@ ccl_device_inline float3 curve_refine(KernelGlobals *kg,
 			sd->Ng = normalize(-(D - tg * (dot(tg, D))));
 		}
 		else {
-			/* direction from inside to surface of curve */
-			float3 p_curr = curvepoint(isect->u, p[0], p[1], p[2], p[3]);
-			sd->Ng = normalize(P - p_curr);
+#ifdef __EMBREE__
+ 			if(kernel_data.bvh.scene) {
+ 				sd->Ng = normalize(isect->Ng);
+ 			}
+ 			else
+#endif
+			{
+				/* direction from inside to surface of curve */
+				float3 p_curr = curvepoint(isect->u, p[0], p[1], p[2], p[3]);
+				sd->Ng = normalize(P - p_curr);
 
-			/* adjustment for changing radius */
-			float gd = isect->v;
+				/* adjustment for changing radius */
+				float gd = isect->v;
 
-			if(gd != 0.0f) {
-				sd->Ng = sd->Ng - gd * tg;
-				sd->Ng = normalize(sd->Ng);
+				if(gd != 0.0f) {
+					sd->Ng = sd->Ng - gd * tg;
+					sd->Ng = normalize(sd->Ng);
+				}
 			}
 		}
 
diff --git a/intern/cycles/kernel/geom/geom_object.h b/intern/cycles/kernel/geom/geom_object.h
index 0eb8ce2cf8b..669c932d720 100644
--- a/intern/cycles/kernel/geom/geom_object.h
+++ b/intern/cycles/kernel/geom/geom_object.h
@@ -78,6 +78,12 @@ ccl_device_inline Transform object_fetch_transform_motion(KernelGlobals *kg, int
 	const uint num_steps = kernel_tex_fetch(__objects, object).numsteps * 2 + 1;
 
 	Transform tfm;
+#ifdef __EMBREE__
+	if(kernel_data.bvh.scene) {
+		transform_motion_array_interpolate_straight(&tfm, motion, num_steps, time);
+	}
+	else
+#endif
 	transform_motion_array_interpolate(&tfm, motion, num_steps, time);
 
 	return tfm;