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Fix #112003: Principled Huang Hair renders black on horizontal particle hair

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Curve normal is not available in legacy particle hair system. Construct
a local coordinate system instead of using a fixed normal direction [1,
0, 0] to avoid black appearance.
This commit is contained in:
Weizhen Huang 2023-09-06 14:03:10 +02:00
parent c1e11df732
commit 077022e45f
3 changed files with 16 additions and 9 deletions
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4
intern/cycles/blender/curves.cpp
View File

@ -335,8 +335,8 @@ static void ExportCurveSegments(Scene *scene, Hair *hair, ParticleCurveData *CDa
if (attr_normal) {
/* NOTE: the geometry normals are not computed for legacy particle hairs. This hair
* system is expected to be discarded. */
attr_normal->add(make_float3(1.0f, 0.0f, 0.0f));
* system is expected to be deprecated. */
attr_normal->add(make_float3(0.0f, 0.0f, 0.0f));
}
num_curve_keys++;

13
intern/cycles/kernel/closure/bsdf_principled_hair_huang.h
View File

@ -211,11 +211,18 @@ ccl_device int bsdf_hair_huang_setup(ccl_private ShaderData *sd,
/* Align local frame with the ray direction so that `phi_i == 0`. */
bsdf->N = X;
}
kernel_assert(!is_zero(bsdf->N) && isfinite_safe(bsdf->N));
/* Fill extra closure. */
bsdf->extra->Z = safe_normalize(cross(bsdf->N, sd->dPdu));
bsdf->extra->Y = safe_normalize(cross(bsdf->extra->Z, bsdf->N));
if (is_zero(bsdf->N) || !isfinite_safe(bsdf->N)) {
bsdf->extra->Y = Y;
/* Construct arbitrary local coordinate system. The implementation should ensure smooth
* transition along the hair shaft. */
make_orthonormals(Y, &bsdf->extra->Z, &bsdf->N);
}
else {
bsdf->extra->Z = safe_normalize(cross(bsdf->N, sd->dPdu));
bsdf->extra->Y = safe_normalize(cross(bsdf->extra->Z, bsdf->N));
}
const float3 I = make_float3(
dot(sd->wi, bsdf->N), dot(sd->wi, bsdf->extra->Y), dot(sd->wi, bsdf->extra->Z));

8
source/blender/nodes/shader/nodes/node_shader_bsdf_hair_principled.cc
View File

@ -48,10 +48,10 @@ static void node_declare(NodeDeclarationBuilder &b)
.max(1.0f)
.subtype(PROP_FACTOR)
.description(
"For elliptical hair cross-section, the aspect ratio is the ratio of the minor axis to "
"the major axis (the major axis is aligned with the curve normal). Recommended values "
"are 0.8~1 for Asian hair, 0.65~0.9 for Caucasian hair, 0.5~0.65 for African hair. Set "
"this to 1 for circular cross-section");
"The ratio of the minor axis to the major axis of an elliptical cross-section. "
"Recommended values are 0.8~1 for Asian hair, 0.65~0.9 for Caucasian hair, 0.5~0.65 for "
"African hair. The major axis is aligned with the curve normal, which is not supported "
"in particle hair");
b.add_input<decl::Float>("Roughness")
.default_value(0.3f)
.min(0.0f)