5078b9d2d0
This is a physically-based, easy-to-use shader for rendering hair and fur, with controls for melanin, roughness and randomization. Based on the paper "A Practical and Controllable Hair and Fur Model for Production Path Tracing". Implemented by Leonardo E. Segovia and Lukas Stockner, part of Google Summer of Code 2018.
247 lines
6.9 KiB
C++
247 lines
6.9 KiB
C++
/*
|
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
|
* you may not use this file except in compliance with the License.
|
|
* You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
* See the License for the specific language governing permissions and
|
|
* limitations under the License.
|
|
*/
|
|
|
|
CCL_NAMESPACE_BEGIN
|
|
|
|
/* Curve Primitive
|
|
*
|
|
* Curve primitive for rendering hair and fur. These can be render as flat
|
|
* ribbons or curves with actual thickness. The curve can also be rendered as
|
|
* line segments rather than curves for better performance.
|
|
*/
|
|
|
|
#ifdef __HAIR__
|
|
|
|
/* Interpolation of curve geometry */
|
|
|
|
ccl_device_inline float3 curvetangent(float t, float3 p0, float3 p1, float3 p2, float3 p3)
|
|
{
|
|
float fc = 0.71f;
|
|
float data[4];
|
|
float t2 = t * t;
|
|
data[0] = -3.0f * fc * t2 + 4.0f * fc * t - fc;
|
|
data[1] = 3.0f * (2.0f - fc) * t2 + 2.0f * (fc - 3.0f) * t;
|
|
data[2] = 3.0f * (fc - 2.0f) * t2 + 2.0f * (3.0f - 2.0f * fc) * t + fc;
|
|
data[3] = 3.0f * fc * t2 - 2.0f * fc * t;
|
|
return data[0] * p0 + data[1] * p1 + data[2] * p2 + data[3] * p3;
|
|
}
|
|
|
|
ccl_device_inline float3 curvepoint(float t, float3 p0, float3 p1, float3 p2, float3 p3)
|
|
{
|
|
float data[4];
|
|
float fc = 0.71f;
|
|
float t2 = t * t;
|
|
float t3 = t2 * t;
|
|
data[0] = -fc * t3 + 2.0f * fc * t2 - fc * t;
|
|
data[1] = (2.0f - fc) * t3 + (fc - 3.0f) * t2 + 1.0f;
|
|
data[2] = (fc - 2.0f) * t3 + (3.0f - 2.0f * fc) * t2 + fc * t;
|
|
data[3] = fc * t3 - fc * t2;
|
|
return data[0] * p0 + data[1] * p1 + data[2] * p2 + data[3] * p3;
|
|
}
|
|
|
|
/* Reading attributes on various curve elements */
|
|
|
|
ccl_device float curve_attribute_float(KernelGlobals *kg, const ShaderData *sd, const AttributeDescriptor desc, float *dx, float *dy)
|
|
{
|
|
if(desc.element == ATTR_ELEMENT_CURVE) {
|
|
#ifdef __RAY_DIFFERENTIALS__
|
|
if(dx) *dx = 0.0f;
|
|
if(dy) *dy = 0.0f;
|
|
#endif
|
|
|
|
return kernel_tex_fetch(__attributes_float, desc.offset + sd->prim);
|
|
}
|
|
else if(desc.element == ATTR_ELEMENT_CURVE_KEY || desc.element == ATTR_ELEMENT_CURVE_KEY_MOTION) {
|
|
float4 curvedata = kernel_tex_fetch(__curves, sd->prim);
|
|
int k0 = __float_as_int(curvedata.x) + PRIMITIVE_UNPACK_SEGMENT(sd->type);
|
|
int k1 = k0 + 1;
|
|
|
|
float f0 = kernel_tex_fetch(__attributes_float, desc.offset + k0);
|
|
float f1 = kernel_tex_fetch(__attributes_float, desc.offset + k1);
|
|
|
|
#ifdef __RAY_DIFFERENTIALS__
|
|
if(dx) *dx = sd->du.dx*(f1 - f0);
|
|
if(dy) *dy = 0.0f;
|
|
#endif
|
|
|
|
return (1.0f - sd->u)*f0 + sd->u*f1;
|
|
}
|
|
else {
|
|
#ifdef __RAY_DIFFERENTIALS__
|
|
if(dx) *dx = 0.0f;
|
|
if(dy) *dy = 0.0f;
|
|
#endif
|
|
|
|
return 0.0f;
|
|
}
|
|
}
|
|
|
|
ccl_device float3 curve_attribute_float3(KernelGlobals *kg, const ShaderData *sd, const AttributeDescriptor desc, float3 *dx, float3 *dy)
|
|
{
|
|
if(desc.element == ATTR_ELEMENT_CURVE) {
|
|
/* idea: we can't derive any useful differentials here, but for tiled
|
|
* mipmap image caching it would be useful to avoid reading the highest
|
|
* detail level always. maybe a derivative based on the hair density
|
|
* could be computed somehow? */
|
|
#ifdef __RAY_DIFFERENTIALS__
|
|
if(dx) *dx = make_float3(0.0f, 0.0f, 0.0f);
|
|
if(dy) *dy = make_float3(0.0f, 0.0f, 0.0f);
|
|
#endif
|
|
|
|
return float4_to_float3(kernel_tex_fetch(__attributes_float3, desc.offset + sd->prim));
|
|
}
|
|
else if(desc.element == ATTR_ELEMENT_CURVE_KEY || desc.element == ATTR_ELEMENT_CURVE_KEY_MOTION) {
|
|
float4 curvedata = kernel_tex_fetch(__curves, sd->prim);
|
|
int k0 = __float_as_int(curvedata.x) + PRIMITIVE_UNPACK_SEGMENT(sd->type);
|
|
int k1 = k0 + 1;
|
|
|
|
float3 f0 = float4_to_float3(kernel_tex_fetch(__attributes_float3, desc.offset + k0));
|
|
float3 f1 = float4_to_float3(kernel_tex_fetch(__attributes_float3, desc.offset + k1));
|
|
|
|
#ifdef __RAY_DIFFERENTIALS__
|
|
if(dx) *dx = sd->du.dx*(f1 - f0);
|
|
if(dy) *dy = make_float3(0.0f, 0.0f, 0.0f);
|
|
#endif
|
|
|
|
return (1.0f - sd->u)*f0 + sd->u*f1;
|
|
}
|
|
else {
|
|
#ifdef __RAY_DIFFERENTIALS__
|
|
if(dx) *dx = make_float3(0.0f, 0.0f, 0.0f);
|
|
if(dy) *dy = make_float3(0.0f, 0.0f, 0.0f);
|
|
#endif
|
|
|
|
return make_float3(0.0f, 0.0f, 0.0f);
|
|
}
|
|
}
|
|
|
|
/* Curve thickness */
|
|
|
|
ccl_device float curve_thickness(KernelGlobals *kg, ShaderData *sd)
|
|
{
|
|
float r = 0.0f;
|
|
|
|
if(sd->type & PRIMITIVE_ALL_CURVE) {
|
|
float4 curvedata = kernel_tex_fetch(__curves, sd->prim);
|
|
int k0 = __float_as_int(curvedata.x) + PRIMITIVE_UNPACK_SEGMENT(sd->type);
|
|
int k1 = k0 + 1;
|
|
|
|
float4 P_curve[2];
|
|
|
|
if(sd->type & PRIMITIVE_CURVE) {
|
|
P_curve[0]= kernel_tex_fetch(__curve_keys, k0);
|
|
P_curve[1]= kernel_tex_fetch(__curve_keys, k1);
|
|
}
|
|
else {
|
|
motion_curve_keys(kg, sd->object, sd->prim, sd->time, k0, k1, P_curve);
|
|
}
|
|
|
|
r = (P_curve[1].w - P_curve[0].w) * sd->u + P_curve[0].w;
|
|
}
|
|
|
|
return r*2.0f;
|
|
}
|
|
|
|
/* Curve location for motion pass, linear interpolation between keys and
|
|
* ignoring radius because we do the same for the motion keys */
|
|
|
|
ccl_device float3 curve_motion_center_location(KernelGlobals *kg, ShaderData *sd)
|
|
{
|
|
float4 curvedata = kernel_tex_fetch(__curves, sd->prim);
|
|
int k0 = __float_as_int(curvedata.x) + PRIMITIVE_UNPACK_SEGMENT(sd->type);
|
|
int k1 = k0 + 1;
|
|
|
|
float4 P_curve[2];
|
|
|
|
P_curve[0]= kernel_tex_fetch(__curve_keys, k0);
|
|
P_curve[1]= kernel_tex_fetch(__curve_keys, k1);
|
|
|
|
return float4_to_float3(P_curve[1]) * sd->u + float4_to_float3(P_curve[0]) * (1.0f - sd->u);
|
|
}
|
|
|
|
/* Curve tangent normal */
|
|
|
|
ccl_device float3 curve_tangent_normal(KernelGlobals *kg, ShaderData *sd)
|
|
{
|
|
float3 tgN = make_float3(0.0f,0.0f,0.0f);
|
|
|
|
if(sd->type & PRIMITIVE_ALL_CURVE) {
|
|
|
|
tgN = -(-sd->I - sd->dPdu * (dot(sd->dPdu,-sd->I) / len_squared(sd->dPdu)));
|
|
tgN = normalize(tgN);
|
|
|
|
/* need to find suitable scaled gd for corrected normal */
|
|
#if 0
|
|
tgN = normalize(tgN - gd * sd->dPdu);
|
|
#endif
|
|
}
|
|
|
|
return tgN;
|
|
}
|
|
|
|
/* Curve bounds utility function */
|
|
|
|
ccl_device_inline void curvebounds(float *lower, float *upper, float *extremta, float *extrema, float *extremtb, float *extremb, float p0, float p1, float p2, float p3)
|
|
{
|
|
float halfdiscroot = (p2 * p2 - 3 * p3 * p1);
|
|
float ta = -1.0f;
|
|
float tb = -1.0f;
|
|
|
|
*extremta = -1.0f;
|
|
*extremtb = -1.0f;
|
|
*upper = p0;
|
|
*lower = (p0 + p1) + (p2 + p3);
|
|
*extrema = *upper;
|
|
*extremb = *lower;
|
|
|
|
if(*lower >= *upper) {
|
|
*upper = *lower;
|
|
*lower = p0;
|
|
}
|
|
|
|
if(halfdiscroot >= 0) {
|
|
float inv3p3 = (1.0f/3.0f)/p3;
|
|
halfdiscroot = sqrtf(halfdiscroot);
|
|
ta = (-p2 - halfdiscroot) * inv3p3;
|
|
tb = (-p2 + halfdiscroot) * inv3p3;
|
|
}
|
|
|
|
float t2;
|
|
float t3;
|
|
|
|
if(ta > 0.0f && ta < 1.0f) {
|
|
t2 = ta * ta;
|
|
t3 = t2 * ta;
|
|
*extremta = ta;
|
|
*extrema = p3 * t3 + p2 * t2 + p1 * ta + p0;
|
|
|
|
*upper = fmaxf(*extrema, *upper);
|
|
*lower = fminf(*extrema, *lower);
|
|
}
|
|
|
|
if(tb > 0.0f && tb < 1.0f) {
|
|
t2 = tb * tb;
|
|
t3 = t2 * tb;
|
|
*extremtb = tb;
|
|
*extremb = p3 * t3 + p2 * t2 + p1 * tb + p0;
|
|
|
|
*upper = fmaxf(*extremb, *upper);
|
|
*lower = fminf(*extremb, *lower);
|
|
}
|
|
}
|
|
|
|
#endif /* __HAIR__ */
|
|
|
|
CCL_NAMESPACE_END
|