Commit: 4443bb89228098a7b7eecdf4899a46aee5061bce
Author: Brecht Van Lommel
Date: Thu Feb 4 23:35:08 2016 +0100
Branches: master
https://developer.blender.org/rB4443bb89228098a7b7eecdf4899a46aee5061bce
Fix Burley BSSRDF NaNs and fireflies.
Explicitly truncate to Rm same way as the Gaussian BSSRDF, and use safe_sqrtf()
to be sure in case of float precision issues.
===================================================================
M intern/cycles/kernel/closure/bssrdf.h
M intern/cycles/kernel/kernel_subsurface.h
===================================================================
diff --git a/intern/cycles/kernel/closure/bssrdf.h
b/intern/cycles/kernel/closure/bssrdf.h
index c2fde6f..a53fedb 100644
--- a/intern/cycles/kernel/closure/bssrdf.h
+++ b/intern/cycles/kernel/closure/bssrdf.h
@@ -65,7 +65,7 @@ ccl_device void bssrdf_gaussian_sample(ShaderClosure *sc,
float xi, float *r, fl
*r = sqrtf(r_squared);
/* h^2 + r^2 = Rm^2 */
- *h = sqrtf(Rm*Rm - r_squared);
+ *h = safe_sqrtf(Rm*Rm - r_squared);
}
/* Planar Cubic BSSRDF falloff
@@ -170,13 +170,20 @@ ccl_device void bssrdf_cubic_sample(ShaderClosure *sc,
float xi, float *r, float
*r = r_;
/* h^2 + r^2 = Rm^2 */
- *h = sqrtf(Rm*Rm - r_*r_);
+ *h = safe_sqrtf(Rm*Rm - r_*r_);
}
/* Approximate Reflectance Profiles
* http://graphics.pixar.com/library/ApproxBSSRDF/paper.pdf
*/
+/* 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.
+ */
+#define BURLEY_TRUNCATE 10.0f
+#define BURLEY_TRUNCATE_CDF 0.973233f // cdf(BURLEY_TRUNCATE)
+
ccl_device_inline float bssrdf_burley_fitting(float A)
{
/* Diffuse surface transmission, equation (6). */
@@ -200,28 +207,33 @@ ccl_device void bssrdf_burley_setup(ShaderClosure *sc)
const float s = bssrdf_burley_fitting(A);
const float d = l / s;
- sc->custom1 = l;
- sc->custom2 = s;
- sc->custom3 = d;
+ sc->custom1 = d;
}
ccl_device float bssrdf_burley_eval(ShaderClosure *sc, float r)
{
- const float l = sc->custom1,
- s = sc->custom2;
+ const float d = sc->custom1;
+ const float Rm = BURLEY_TRUNCATE * d;
+
+ if (r >= Rm)
+ return 0.0f;
+
+ /* Clamp to avoid precision issues computing expf(-x)/x */
+ r = fmaxf(r, 1e-2f * d);
+
/* Burley refletance profile, equation (3).
*
* Note that surface albedo is already included into sc->weight, no
need to
* multiply by this term here.
*/
- float exp_r_3_d = expf(-s*r / (3.0f * l));
+ float exp_r_3_d = expf(-r / (3.0f * d));
float exp_r_d = exp_r_3_d * exp_r_3_d * exp_r_3_d;
- return s * (exp_r_d + exp_r_3_d) / (8*M_PI_F*l*r);
+ return (exp_r_d + exp_r_3_d) / (8*M_PI_F*d*r);
}
ccl_device float bssrdf_burley_pdf(ShaderClosure *sc, float r)
{
- return bssrdf_burley_eval(sc, r);
+ return bssrdf_burley_eval(sc, r) * (1.0f/BURLEY_TRUNCATE_CDF);
}
/* Find the radius for desired CDF value.
@@ -269,18 +281,14 @@ ccl_device void bssrdf_burley_sample(ShaderClosure *sc,
float *r,
float *h)
{
- 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.
- */
- const float Rm = 10.0f*d;
- const float r_ = bssrdf_burley_root_find(xi) * d;
+ const float d = sc->custom1;
+ const float Rm = BURLEY_TRUNCATE * d;
+ const float r_ = bssrdf_burley_root_find(xi * BURLEY_TRUNCATE_CDF) * d;
*r = r_;
/* h^2 + r^2 = Rm^2 */
- *h = sqrtf(Rm*Rm - r_*r_);
+ *h = safe_sqrtf(Rm*Rm - r_*r_);
}
/* None BSSRDF falloff
@@ -312,7 +320,7 @@ ccl_device void bssrdf_none_sample(ShaderClosure *sc, float
xi, float *r, float
*r = r_;
/* h^2 + r^2 = Rm^2 */
- *h = sqrtf(Rm*Rm - r_*r_);
+ *h = safe_sqrtf(Rm*Rm - r_*r_);
}
/* Generic */
diff --git a/intern/cycles/kernel/kernel_subsurface.h
b/intern/cycles/kernel/kernel_subsurface.h
index 836ba64..705b57b 100644
--- a/intern/cycles/kernel/kernel_subsurface.h
+++ b/intern/cycles/kernel/kernel_subsurface.h
@@ -106,8 +106,6 @@ ccl_device float3 subsurface_scatter_eval(ShaderData *sd,
ShaderClosure *sc, flo
float sample_weight_inv = 1.0f/sample_weight_sum;
- //printf("num closures %d\n", sd->num_closure);
-
for(int i = 0; i < sd->num_closure; i++) {
sc = &sd->closure[i];
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