[Bf-blender-cvs] [263925058ee] soc-2018-hair-shader: Documentation: self-document the shader code
L. E. Segovia
noreply at git.blender.org
Thu Jun 28 01:04:43 CEST 2018
Commit: 263925058ee07e8b5a2cd2dbb53f7910f8741825
Author: L. E. Segovia
Date: Wed Jun 27 23:03:38 2018 +0000
Branches: soc-2018-hair-shader
https://developer.blender.org/rB263925058ee07e8b5a2cd2dbb53f7910f8741825
Documentation: self-document the shader code
I don't think Blender needs it, but it'll be useful for me when
I start writing the relevant chapters of my thesis.
===================================================================
M intern/cycles/kernel/closure/bsdf_hair_principled.h
M intern/cycles/kernel/svm/svm_closure.h
M intern/cycles/render/nodes.cpp
M intern/cycles/render/nodes.h
M source/blender/nodes/shader/nodes/node_shader_bsdf_hair_principled.c
===================================================================
diff --git a/intern/cycles/kernel/closure/bsdf_hair_principled.h b/intern/cycles/kernel/closure/bsdf_hair_principled.h
index 972fe08f975..f9a9d1dc3ba 100644
--- a/intern/cycles/kernel/closure/bsdf_hair_principled.h
+++ b/intern/cycles/kernel/closure/bsdf_hair_principled.h
@@ -26,20 +26,29 @@
CCL_NAMESPACE_BEGIN
typedef ccl_addr_space struct PrincipledHairExtra {
+ /* Geometry data. */
float4 geom;
} PrincipledHairExtra;
typedef ccl_addr_space struct PrincipledHairBSDF {
SHADER_CLOSURE_BASE;
+ /* Absorption coefficient. */
float3 sigma;
+ /* Variance of the underlying logistic distribution. */
float v;
+ /* Scale factor of the underlying logistic distribution. */
float s;
+ /* Cuticle tilt angle. */
float alpha;
+ /* IOR. */
float eta;
+ /* Effective variance for the diffuse bounce only. */
float m0_roughness;
+ /* Random number sample (unused). */
float random;
+ /* Extra closure. */
PrincipledHairExtra *extra;
} PrincipledHairBSDF;
@@ -52,10 +61,12 @@ ccl_device_inline float cos_from_sin(const float s)
}
/* Gives the change in direction in the normal plane for the given angles and p-th-order scattering. */
-ccl_device_inline float delta_phi(int p, float gamma_o, float gamma_t) {
+ccl_device_inline float delta_phi(int p, float gamma_o, float gamma_t)
+{
return 2.0f * p * gamma_t - 2.0f * gamma_o + p * M_PI_F;
}
+/* Remaps the given angle to [-pi, pi]. */
ccl_device_inline float wrap_angle(float a)
{
while(a > M_PI_F) a -= M_2PI_F;
@@ -63,12 +74,14 @@ ccl_device_inline float wrap_angle(float a)
return a;
}
+/* Logistic distribution function. */
ccl_device_inline float logistic(float x, float s)
{
float v = expf(-fabsf(x)/s);
return v / (s * sqr(1.0f + v));
}
+/* Logistic cumulative density function. */
ccl_device_inline float logistic_cdf(float x, float s)
{
float arg = -x/s;
@@ -77,6 +90,7 @@ ccl_device_inline float logistic_cdf(float x, float s)
return 1.0f / (1.0f + expf(arg));
}
+/* Numerical approximation to the Bessel function of the first kind. */
ccl_device_inline float bessel_I0(float x)
{
x = sqr(x);
@@ -95,6 +109,7 @@ ccl_device_inline float bessel_I0(float x)
return val;
}
+/* Logarithm of the Bessel function of the first kind. */
ccl_device_inline float log_bessel_I0(float x)
{
if (x > 12.0f) {
@@ -107,7 +122,7 @@ ccl_device_inline float log_bessel_I0(float x)
}
}
-/* Logistic distribution limited to the interval from -pi to pi. */
+/* Logistic distribution limited to the interval [-pi, pi]. */
ccl_device_inline float trimmed_logistic(float x, float s)
{
/* The logistic distribution is symmetric and centered around zero,
@@ -118,6 +133,7 @@ ccl_device_inline float trimmed_logistic(float x, float s)
return safe_divide(val, scaling_fac);
}
+/* Sampling function for the trimmed logistic function. */
ccl_device_inline float sample_trimmed_logistic(float u, float s)
{
float cdf_minuspi = logistic_cdf(-M_PI_F, s);
@@ -125,6 +141,7 @@ ccl_device_inline float sample_trimmed_logistic(float u, float s)
return clamp(x, -M_PI_F, M_PI_F);
}
+/* Azimuthal scattering function Np. */
ccl_device_inline float azimuthal_scattering(float phi, int p, float s, float gamma_o, float gamma_t)
{
float phi_o = wrap_angle(phi - delta_phi(p, gamma_o, gamma_t));
@@ -133,6 +150,7 @@ ccl_device_inline float azimuthal_scattering(float phi, int p, float s, float ga
return val;
}
+/* Longitudinal scattering function Mp. */
ccl_device_inline float longitudinal_scattering(float sin_theta_i, float cos_theta_i, float sin_theta_o, float cos_theta_o, float v)
{
float inv_v = 1.0f/v;
@@ -152,13 +170,14 @@ ccl_device_inline float longitudinal_scattering(float sin_theta_i, float cos_the
}
}
+/* Combine the three values using their luminances. */
ccl_device_inline float4 combine_with_energy(KernelGlobals *kg, float3 c)
{
return make_float4(c.x, c.y, c.z, linear_rgb_to_gray(kg, c));
}
#ifdef __HAIR__
-
+/* Set up the hair closure. */
ccl_device int bsdf_principled_hair_setup(ShaderData *sd, PrincipledHairBSDF *bsdf)
{
// if((sd->type & PRIMITIVE_ALL_CURVE) == 0) {
@@ -170,6 +189,7 @@ ccl_device int bsdf_principled_hair_setup(ShaderData *sd, PrincipledHairBSDF *bs
bsdf->v = clamp(bsdf->v, 0.001f, 0.999f);
bsdf->s = clamp(bsdf->s, 0.001f, 0.999f);
+ /* Map from roughness_u and roughness_v to variance and scale factor. */
bsdf->v = sqr(0.726f*bsdf->v + 0.812f*sqr(bsdf->v) + 3.700f*pow20(bsdf->v));
bsdf->s = (0.265f*bsdf->s + 1.194f*sqr(bsdf->s) + 5.372f*pow22(bsdf->s))*M_SQRT_PI_8_F;
bsdf->m0_roughness = clamp(bsdf->m0_roughness*bsdf->v, 0.001f, 0.999f);
@@ -214,7 +234,8 @@ ccl_device int bsdf_principled_hair_setup(ShaderData *sd, PrincipledHairBSDF *bs
#endif /* __HAIR__ */
-ccl_device_inline void hair_ap(KernelGlobals *kg, float f, float3 T, float4 *Ap)
+/* Given the Fresnel term and transmittance, generate the attenuation terms for each bounce. */
+ccl_device_inline void hair_attenuation(KernelGlobals *kg, float f, float3 T, float4 *Ap)
{
/* Primary specular (R). */
Ap[0] = make_float4(f, f, f, f);
@@ -227,7 +248,7 @@ ccl_device_inline void hair_ap(KernelGlobals *kg, float f, float3 T, float4 *Ap)
col *= T*f;
Ap[2] = combine_with_energy(kg, col);
- /* Residual component. */
+ /* Residual component (TRRT+). */
col *= safe_divide_color(T*f, make_float3(1.0f, 1.0f, 1.0f) - T*f);
Ap[3] = combine_with_energy(kg, col);
@@ -241,6 +262,7 @@ ccl_device_inline void hair_ap(KernelGlobals *kg, float f, float3 T, float4 *Ap)
Ap[3].w *= fac;
}
+/* Given the tilt angle, generate the rotated theta_i for the different bounces. */
ccl_device_inline void hair_alpha_angles(float sin_theta_i, float cos_theta_i, float alpha, float *angles)
{
float sin_1alpha = sinf(alpha);
@@ -258,6 +280,7 @@ ccl_device_inline void hair_alpha_angles(float sin_theta_i, float cos_theta_i, f
angles[5] = fabsf(cos_theta_i*cos_4alpha + sin_theta_i*sin_4alpha);
}
+/* Evaluation function for our shader. */
ccl_device float3 bsdf_principled_hair_eval(KernelGlobals *kg, const ShaderData *sd, const ShaderClosure *sc, const float3 omega_in, float *pdf)
{
//*pdf = 0.0f;
@@ -294,7 +317,7 @@ ccl_device float3 bsdf_principled_hair_eval(KernelGlobals *kg, const ShaderData
float3 T = exp3(-bsdf->sigma * (2.0f * cos_gamma_t / cos_theta_t));
float4 Ap[4];
- hair_ap(kg, fresnel_dielectric_cos(cos_theta_o * cos_gamma_o, bsdf->eta), T, Ap);
+ hair_attenuation(kg, fresnel_dielectric_cos(cos_theta_o * cos_gamma_o, bsdf->eta), T, Ap);
//printf("%f %f %f %f\n%f %f %f %f\n%f %f %f %f\n%f %f %f %f\n", (double)Ap[0].x, (double)Ap[0].y, (double)Ap[0].z, (double)Ap[0].w, (double)Ap[1].x, (double)Ap[1].y, (double)Ap[1].z, (double)Ap[1].w, (double)Ap[2].x, (double)Ap[2].y, (double)Ap[2].z, (double)Ap[2].w, (double)Ap[3].x, (double)Ap[3].y, (double)Ap[3].z, (double)Ap[3].w);
@@ -311,25 +334,25 @@ ccl_device float3 bsdf_principled_hair_eval(KernelGlobals *kg, const ShaderData
float4 F;
float Mp, Np;
- // R
+ /* Primary specular (R). */
Mp = longitudinal_scattering(angles[0], angles[1], sin_theta_o, cos_theta_o, bsdf->m0_roughness);
Np = azimuthal_scattering(phi, 0, bsdf->s, gamma_o, gamma_t);
F = Ap[0] * Mp * Np;
kernel_assert(isfinite3_safe(float4_to_float3(F)));
- // TT
+ /* Transmission (TT). */
Mp = longitudinal_scattering(angles[2], angles[3], sin_theta_o, cos_theta_o, 0.25f*bsdf->v);
Np = azimuthal_scattering(phi, 1, bsdf->s, gamma_o, gamma_t);
F += Ap[1] * Mp * Np;
kernel_assert(isfinite3_safe(float4_to_float3(F)));
- // TRT
+ /* Secondary specular (TRT). */
Mp = longitudinal_scattering(angles[4], angles[5], sin_theta_o, cos_theta_o, 4.0f*bsdf->v);
Np = azimuthal_scattering(phi, 2, bsdf->s, gamma_o, gamma_t);
F += Ap[2] * Mp * Np;
kernel_assert(isfinite3_safe(float4_to_float3(F)));
- // TRRT+
+ /* Residual component (TRRT+). */
Mp = longitudinal_scattering(sin_theta_i, cos_theta_i, sin_theta_o, cos_theta_o, 4.0f*bsdf->v);
Np = M_1_2PI_F;
F += Ap[3] * Mp * Np;
@@ -341,6 +364,7 @@ ccl_device float3 bsdf_principled_hair_eval(KernelGlobals *kg, const ShaderData
return float4_to_float3(F);
}
+/* Sampling function for the hair shader. (It should correspond directly to the evaluation function.) */
ccl_device int bsdf_principled_hair_sample(KernelGlobals *kg, const ShaderClosure *sc, ShaderData *sd, float randu, float randv, float3 *eval, float3 *omega_in, float3 *domega_in_dx, float3 *domega_in_dy, float *pdf)
{
#ifdef __KERNEL_CPU__
@@ -382,7 +406,7 @@ ccl_device int bsdf_principled_hair_sample(KernelGlobals *kg, const ShaderClosur
float3 T = exp3(-bsdf->sigma * (2.0f * cos_gamma_t / cos_theta_t));
float4 Ap[4];
- hair_ap(kg, fresnel_dielectric_cos(cos_theta_o * cos_gamma_o, bsdf->eta), T, Ap);
+ hair_attenuation(kg, fresnel_dielectric_cos(cos_theta_o * cos_gamma_o, bsdf->eta), T, Ap);
//printf("%f %f %f %f\n%f %f %f %f\n%f %f %f %f\n%f %f %f %f\n", (double)Ap[0].x, (double)Ap[0].y, (double)Ap[0].z, (double)Ap[0].w, (double)Ap[1].x, (double)Ap[1].y, (double)Ap[1].z, (double)Ap[1].w, (double)Ap[2].x, (double)Ap[2].y, (double)Ap[2].z, (double)Ap[2].w, (double)Ap[3].x, (double)Ap[3].y, (double)Ap[3].z, (double)Ap[3].w);
@@ -430,25 +454,25 @@ ccl_device int bsdf_principled_hair_sample(KernelGlobals *kg, const ShaderClosur
float4 F;
float Mp, Np;
- // R
+ /* Primary specular (R). */
Mp = longitudinal_scattering(angles[0], angles[1], sin_theta_o, cos_theta_o, bsdf->m0_roughness);
Np = azimuthal_scattering(phi, 0, bsdf->s, gamma_o, gamma_t);
F = Ap[0] * Mp * Np;
kernel_assert(isfinite3_safe(float4_to_float3(F)));
- // TT
+ /* Transmission (TT). */
Mp = longitudinal_scattering(angles[2], angles[3], sin_theta_o, cos_theta_o, 0.25f*bsdf->v);
Np = azimuthal_scattering(phi, 1, bsdf->s, gamma_o, gamma_t);
F += Ap[1] * Mp * Np;
kernel_assert(isfinite3_safe(float4_to_float3(F)));
- // TRT
+ /* Secondary specular (TRT). */
Mp = longitudinal_scattering(angles[4], angles[5], sin_theta_o, cos_theta_o, 4.0f*bsdf->v);
Np = azimuthal_scattering(phi, 2, bsdf->s, gamma_o, gamma_t);
F += Ap[2] * Mp * Np;
kernel_assert(isfinite3_safe(float4_to_float3(F)));
- // TRRT+
+ /* Res
@@ Diff output truncated at 10240 characters. @@
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