Cycles Volume Render: scattering support.

This is done by adding a Volume Scatter node. In many cases you will want to
add together a Volume Absorption and Volume Scatter node with the same color
and density to get the expected results.

This should work with branched path tracing, mixing closures, overlapping
volumes, etc. However there's still various optimizations needed for sampling.
The main missing thing from the volume branch is the equiangular sampling for
homogeneous volumes.

The heterogeneous scattering code was arranged such that we can use a single
stratified random number for distance sampling, which gives less noise than
pseudo random numbers for each step. For volumes where the color is textured
there still seems to be something off, needs to be investigated.

1 files changed, 1 insertions, 0 deletions

diff --git a/intern/cycles/kernel/svm/svm_types.h b/intern/cycles/kernel/svm/svm_types.h
index 9850a058611..52bea153a2a 100644
--- a/intern/cycles/kernel/svm/svm_types.h
+++ b/intern/cycles/kernel/svm/svm_types.h
@@ -410,6 +410,7 @@ typedef enum ClosureType {
 #define CLOSURE_IS_HOLDOUT(type) (type == CLOSURE_HOLDOUT_ID)
 #define CLOSURE_IS_BACKGROUND(type) (type == CLOSURE_BACKGROUND_ID)
 #define CLOSURE_IS_AMBIENT_OCCLUSION(type) (type == CLOSURE_AMBIENT_OCCLUSION_ID)
+#define CLOSURE_IS_PHASE(type) (type == CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID)
 
 #define CLOSURE_WEIGHT_CUTOFF 1e-5f