[Bf-blender-cvs] [d1ab751213b] principled-v2: Fix clearcoat tint
Lukas Stockner
noreply at git.blender.org
Mon Jul 4 23:56:15 CEST 2022
Commit: d1ab751213bb1da9498b078ee2c53545aa6c3194
Author: Lukas Stockner
Date: Mon Jul 4 23:31:48 2022 +0200
Branches: principled-v2
https://developer.blender.org/rBd1ab751213bb1da9498b078ee2c53545aa6c3194
Fix clearcoat tint
===================================================================
M intern/cycles/kernel/svm/closure_principled.h
===================================================================
diff --git a/intern/cycles/kernel/svm/closure_principled.h b/intern/cycles/kernel/svm/closure_principled.h
index 7066d72d533..4767c2932ca 100644
--- a/intern/cycles/kernel/svm/closure_principled.h
+++ b/intern/cycles/kernel/svm/closure_principled.h
@@ -450,16 +450,16 @@ ccl_device_inline void principled_v2_diffuse(
sd->flag |= bsdf_diffuse_setup(bsdf);
}
-ccl_device_inline float principled_v2_clearcoat(KernelGlobals kg,
- ccl_private ShaderData *sd,
- ccl_private float *stack,
- float3 weight,
- int path_flag,
- uint data)
+ccl_device_inline float3 principled_v2_clearcoat(KernelGlobals kg,
+ ccl_private ShaderData *sd,
+ ccl_private float *stack,
+ float3 weight,
+ int path_flag,
+ uint data)
{
#ifdef __CAUSTICS_TRICKS__
if (!kernel_data.integrator.caustics_reflective && (path_flag & PATH_RAY_DIFFUSE)) {
- return 0.0f;
+ return one_float3();
}
#endif
@@ -468,7 +468,7 @@ ccl_device_inline float principled_v2_clearcoat(KernelGlobals kg,
float clearcoat = saturatef(stack_load_float(stack, clearcoat_offset));
if (clearcoat <= CLOSURE_WEIGHT_CUTOFF) {
- return 0.0f;
+ return one_float3();
}
float roughness = saturatef(stack_load_float(stack, roughness_offset));
@@ -481,21 +481,35 @@ ccl_device_inline float principled_v2_clearcoat(KernelGlobals kg,
if (tint != one_float3()) {
/* Tint is normalized to perpendicular incidence.
* Therefore, if we define the coating thickness as length 1, the length along the ray is
- * t = tan(angle(N, I)) = tan(acos(dotNI)) = sqrt(1-dotNI^2) / dotNI.
+ * t = sqrt(1+tan^2(angle(N, I))) = sqrt(1+tan^2(acos(dotNI))) = 1 / dotNI.
* From Beer's law, we have T = exp(-sigma_e * t).
* Therefore, tint = exp(-sigma_e * 1) (per def.), so -sigma_e = log(tint).
* From this, T = exp(log(tint) * t) = exp(log(tint)) ^ t = tint ^ t;
+ * Additionally, the strength input controls the optical depth for a smooth fade
+ * from maximum to zero impact.
+ *
+ * Note that this is only an approximation - in particular, the exit path of the
+ * light that bounces off the main layer is not accounted for.
+ * Ideally, we should be attenuating by sqrt(tint) both ways. Currently, the model
+ * is accurate for perfect mirrors since both entry and exit have the same cosNI there,
+ * but if e.g. the base is diffuse and we look at it from a grazing angle, in reality
+ * the cosNI of the exit bounce will be much higher on average, so the tint would be
+ * less extreme.
+ * TODO: Maybe account for this by setting
+ * OD := 0.5*OD + 0.5*lerp(1.59, OD, metallic * (1 - roughness)),
+ * where 1.59 is the closest numerical fit for average optical depth on lambertian reflectors.
+ * That way, mirrors preserve their look, but diffuse-ish objects have a more natural behavior.
*/
float cosNI = dot(sd->I, N);
- float optical_depth = safe_sqrtf(1.0f - sqr(cosNI)) / cosNI;
- tint = pow(tint, optical_depth);
+ float optical_depth = 1.0f / cosNI;
+ tint = pow(tint, optical_depth * clearcoat);
}
ccl_private MicrofacetBsdf *bsdf = (ccl_private MicrofacetBsdf *)bsdf_alloc(
- sd, sizeof(MicrofacetBsdf), tint * clearcoat * weight);
+ sd, sizeof(MicrofacetBsdf), clearcoat * weight);
if (bsdf == NULL) {
- return 0.0f;
+ return one_float3();
}
bsdf->N = N;
@@ -508,7 +522,7 @@ ccl_device_inline float principled_v2_clearcoat(KernelGlobals kg,
/* setup bsdf */
sd->flag |= bsdf_microfacet_ggx_clearcoat_v2_setup(bsdf, sd);
- return clearcoat_E(dot(sd->I, N), roughness) * clearcoat;
+ return tint * (1.0f - clearcoat_E(dot(sd->I, N), roughness) * clearcoat);
}
ccl_device_inline float principled_v2_sheen(KernelGlobals kg,
@@ -523,16 +537,16 @@ ccl_device_inline float principled_v2_sheen(KernelGlobals kg,
float sheen = stack_load_float(stack, sheen_offset);
if (sheen <= CLOSURE_WEIGHT_CUTOFF) {
- return 0.0f;
+ return 1.0f;
}
float3 tint = stack_load_float3(stack, sheen_tint_offset);
float roughness = stack_load_float(stack, sheen_roughness_offset);
ccl_private PrincipledSheenBsdf *bsdf = (ccl_private PrincipledSheenBsdf *)bsdf_alloc(
- sd, sizeof(PrincipledSheenBsdf), sheen * weight); // TODO include tint
+ sd, sizeof(PrincipledSheenBsdf), sheen * weight); // TODO include tint
if (bsdf == NULL) {
- return 0.0f;
+ return 1.0f;
}
bsdf->N = N;
@@ -541,7 +555,7 @@ ccl_device_inline float principled_v2_sheen(KernelGlobals kg,
/* setup bsdf */
sd->flag |= bsdf_principled_sheen_v2_setup(sd, bsdf);
- return sheen * bsdf->avg_value; // TODO include tint
+ return 1.0f - sheen * bsdf->avg_value; // TODO include tint
}
ccl_device_inline float principled_v2_specular(ccl_private ShaderData *sd,
@@ -634,8 +648,8 @@ ccl_device void svm_node_closure_principled_v2(KernelGlobals kg,
float ior = fmaxf(stack_load_float(stack, ior_offset), 1e-5f);
float transmission = saturatef(stack_load_float(stack, transmission_offset));
- weight *= 1.0f - principled_v2_clearcoat(kg, sd, stack, weight, path_flag, node_2.w);
- weight *= 1.0f - principled_v2_sheen(kg, sd, stack, weight, N, node_2.z);
+ weight *= principled_v2_clearcoat(kg, sd, stack, weight, path_flag, node_2.w);
+ weight *= principled_v2_sheen(kg, sd, stack, weight, N, node_2.z);
float dielectric_albedo = principled_v2_specular(sd,
stack,
More information about the Bf-blender-cvs
mailing list