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/*
* Copyright 2011, Blender Foundation.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
CCL_NAMESPACE_BEGIN
struct LightSample {
float3 P;
float3 Ng;
int object;
int prim;
int shader;
float weight;
};
/* Point Light */
__device void point_light_sample(KernelGlobals *kg, int point,
float randu, float randv, float3 P, LightSample *ls)
{
float4 f = kernel_tex_fetch(__light_point, point);
ls->P = make_float3(f.x, f.y, f.z);
ls->Ng = normalize(ls->P - P);
ls->shader = __float_as_int(f.w);
ls->object = ~0;
ls->prim = ~0;
}
__device float point_light_pdf(KernelGlobals *kg, float t)
{
return t*t*kernel_data.integrator.pdf_lights;
}
/* Triangle Light */
__device void triangle_light_sample(KernelGlobals *kg, int prim, int object,
float randu, float randv, LightSample *ls)
{
/* triangle, so get position, normal, shader */
ls->P = triangle_sample_MT(kg, prim, randu, randv);
ls->Ng = triangle_normal_MT(kg, prim, &ls->shader);
ls->object = object;
ls->prim = prim;
#ifdef __INSTANCING__
/* instance transform */
if(ls->object >= 0) {
object_position_transform(kg, ls->object, &ls->P);
object_normal_transform(kg, ls->object, &ls->Ng);
}
#endif
}
__device float triangle_light_pdf(KernelGlobals *kg,
const float3 Ng, const float3 I, float t)
{
float cos_pi = fabsf(dot(Ng, I));
if(cos_pi == 0.0f)
return 0.0f;
return (t*t*kernel_data.integrator.pdf_triangles)/cos_pi;
}
/* Light Distribution */
__device int light_distribution_sample(KernelGlobals *kg, float randt)
{
/* this is basically std::upper_bound as used by pbrt, to find a point light or
triangle to emit from, proportional to area. a good improvement would be to
also sample proportional to power, though it's not so well defined with
OSL shaders. */
int first = 0;
int len = kernel_data.integrator.num_distribution + 1;
while(len > 0) {
int half_len = len >> 1;
int middle = first + half_len;
if(randt < kernel_tex_fetch(__light_distribution, middle).x) {
len = half_len;
}
else {
first = middle + 1;
len = len - half_len - 1;
}
}
first = max(0, first-1);
kernel_assert(first >= 0 && first < kernel_data.integrator.num_distribution);
return first;
}
/* Generic Light */
__device void light_sample(KernelGlobals *kg, float randt, float randu, float randv, float3 P, LightSample *ls)
{
/* sample index */
int index = light_distribution_sample(kg, randt);
/* fetch light data */
float4 l = kernel_tex_fetch(__light_distribution, index);
int prim = __float_as_int(l.y);
ls->weight = l.z;
if(prim >= 0) {
int object = __float_as_int(l.w);
triangle_light_sample(kg, prim, object, randu, randv, ls);
}
else {
int point = -prim-1;
point_light_sample(kg, point, randu, randv, P, ls);
}
}
__device float light_pdf(KernelGlobals *kg, LightSample *ls, float3 I, float t)
{
float pdf;
if(ls->prim != ~0)
pdf = triangle_light_pdf(kg, ls->Ng, I, t);
else
pdf = point_light_pdf(kg, t);
return pdf;
}
CCL_NAMESPACE_END
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