Commit: 3e7389eaf2d7ffbd180931c117776d3de2da5adb
Author: Sergey Sharybin
Date: Thu Feb 4 15:25:29 2016 +0100
Branches: master
https://developer.blender.org/rB3e7389eaf2d7ffbd180931c117776d3de2da5adb
Cycles: Speedup of Christensen-Burley SSS falloff function
The idea is simply to pre-compute fitting and parameterization
in the bssrdf_setup() function and re-use the values in both
sample() and eval().
The only trick is where to store the pre-calculated values and
the answer is inside of ShaderClosure->custom{1,2,3}. There's
no memory bump here because we now simply re-use padding fields
for the pre-calculated values. Similar trick we can do for other
BSDFs.
Seems to give nice speedup up to 7% here on my desktop with
Core i7 CPU, SSE4.1 kernel.
===================================================================
M intern/cycles/kernel/closure/bssrdf.h
M intern/cycles/kernel/kernel_types.h
===================================================================
diff --git a/intern/cycles/kernel/closure/bssrdf.h
b/intern/cycles/kernel/closure/bssrdf.h
index 041832e..522bc36 100644
--- a/intern/cycles/kernel/closure/bssrdf.h
+++ b/intern/cycles/kernel/closure/bssrdf.h
@@ -19,25 +19,6 @@
CCL_NAMESPACE_BEGIN
-ccl_device int bssrdf_setup(ShaderClosure *sc, ClosureType type)
-{
- if(sc->data0 < BSSRDF_MIN_RADIUS) {
- /* revert to diffuse BSDF if radius too small */
- sc->data0 = 0.0f;
- sc->data1 = 0.0f;
- int flag = bsdf_diffuse_setup(sc);
- sc->type = CLOSURE_BSDF_BSSRDF_ID;
- return flag;
- }
- else {
- sc->data1 = saturate(sc->data1); /* texture blur */
- sc->T.x = saturate(sc->T.x); /* sharpness */
- sc->type = type;
-
- return SD_BSDF|SD_BSDF_HAS_EVAL|SD_BSSRDF;
- }
-}
-
/* Planar Truncated Gaussian
*
* Note how this is different from the typical gaussian, this one integrates
@@ -210,13 +191,24 @@ ccl_device_inline float
bssrdf_burley_compatible_mfp(float r)
return 0.5f * M_1_PI_F * r;
}
-ccl_device float bssrdf_burley_eval(ShaderClosure *sc, float r)
+ccl_device void bssrdf_burley_setup(ShaderClosure *sc)
{
/* Mean free path length. */
const float l = bssrdf_burley_compatible_mfp(sc->data0);
/* Surface albedo. */
const float A = sc->data2;
const float s = bssrdf_burley_fitting(A);
+ const float d = l / s;
+
+ sc->custom1 = l;
+ sc->custom2 = s;
+ sc->custom3 = d;
+}
+
+ccl_device float bssrdf_burley_eval(ShaderClosure *sc, float r)
+{
+ const float l = sc->custom1,
+ s = sc->custom2;
/* Burley refletance profile, equation (3).
*
* Note that surface albedo is already included into sc->weight, no
need to
@@ -277,12 +269,7 @@ ccl_device void bssrdf_burley_sample(ShaderClosure *sc,
float *r,
float *h)
{
- /* Mean free path length. */
- const float l = bssrdf_burley_compatible_mfp(sc->data0);
- /* Surface albedo. */
- const float A = sc->data2;
- const float s = bssrdf_burley_fitting(A);
- const float d = l / s;
+ const float d = sc->custom3;
/* This is a bit arbitrary, just need big enough radius so it matches
* the mean free length, but still not too big so sampling is still
* effective. Might need some further tweaks.
@@ -330,6 +317,29 @@ ccl_device void bssrdf_none_sample(ShaderClosure *sc,
float xi, float *r, float
/* Generic */
+ccl_device int bssrdf_setup(ShaderClosure *sc, ClosureType type)
+{
+ if(sc->data0 < BSSRDF_MIN_RADIUS) {
+ /* revert to diffuse BSDF if radius too small */
+ sc->data0 = 0.0f;
+ sc->data1 = 0.0f;
+ int flag = bsdf_diffuse_setup(sc);
+ sc->type = CLOSURE_BSDF_BSSRDF_ID;
+ return flag;
+ }
+ else {
+ sc->data1 = saturate(sc->data1); /* texture blur */
+ sc->T.x = saturate(sc->T.x); /* sharpness */
+ sc->type = type;
+
+ if(type == CLOSURE_BSSRDF_BURLEY_ID) {
+ bssrdf_burley_setup(sc);
+ }
+
+ return SD_BSDF|SD_BSDF_HAS_EVAL|SD_BSSRDF;
+ }
+}
+
ccl_device void bssrdf_sample(ShaderClosure *sc, float xi, float *r, float *h)
{
if(sc->type == CLOSURE_BSSRDF_CUBIC_ID)
diff --git a/intern/cycles/kernel/kernel_types.h
b/intern/cycles/kernel/kernel_types.h
index 93ff732..42d40e1 100644
--- a/intern/cycles/kernel/kernel_types.h
+++ b/intern/cycles/kernel/kernel_types.h
@@ -642,7 +642,14 @@ typedef ccl_addr_space struct ShaderClosure {
float data0;
float data1;
float data2;
- int pad1, pad2, pad3;
+
+ /* Following fields could be used to store pre-calculated
+ * values by various BSDF closures for more effective sampling
+ * and evaluation.
+ */
+ float custom1;
+ float custom2;
+ float custom3;
#ifdef __OSL__
void *prim, *pad4;
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