void LightSampler::sample_emitting_triangle(
const ShadingRay::Time& time,
const Vector2d& s,
const size_t triangle_index,
const double triangle_prob,
LightSample& light_sample) const
{
// Fetch the emitting triangle.
const EmittingTriangle& emitting_triangle = m_emitting_triangles[triangle_index];
assert(emitting_triangle.m_triangle_prob == triangle_prob);
// Store a pointer to the emitting triangle.
light_sample.m_triangle = &emitting_triangle;
// Uniformly sample the surface of the triangle.
const Vector3d bary = sample_triangle_uniform(s);
// Set the barycentric coordinates.
light_sample.m_bary[0] = bary[0];
light_sample.m_bary[1] = bary[1];
// Compute the world space position of the sample.
light_sample.m_point =
bary[0] * emitting_triangle.m_v0
+ bary[1] * emitting_triangle.m_v1
+ bary[2] * emitting_triangle.m_v2;
// Compute the world space shading normal at the position of the sample.
light_sample.m_shading_normal =
bary[0] * emitting_triangle.m_n0
+ bary[1] * emitting_triangle.m_n1
+ bary[2] * emitting_triangle.m_n2;
light_sample.m_shading_normal = normalize(light_sample.m_shading_normal);
// Set the world space geometric normal.
light_sample.m_geometric_normal = emitting_triangle.m_geometric_normal;
// Compute the probability density of this sample.
light_sample.m_probability = triangle_prob * emitting_triangle.m_rcp_area;
}
void LightSampler::sample_emitting_triangle(
const Vector2d& s,
const size_t triangle_index,
const double triangle_prob,
LightSample& sample) const
{
// Fetch and set the emitting triangle.
const EmittingTriangle& triangle = m_emitting_triangles[triangle_index];
sample.m_triangle = ▵
// Uniformly sample the surface of the triangle.
const Vector3d bary = sample_triangle_uniform(s);
// Set the barycentric coordinates.
sample.m_bary[0] = bary[0];
sample.m_bary[1] = bary[1];
// Compute the world space position of the sample.
sample.m_point =
bary[0] * triangle.m_v0
+ bary[1] * triangle.m_v1
+ bary[2] * triangle.m_v2;
// Compute the world space shading normal at the position of the sample.
sample.m_shading_normal =
bary[0] * triangle.m_n0
+ bary[1] * triangle.m_n1
+ bary[2] * triangle.m_n2;
sample.m_shading_normal = normalize(sample.m_shading_normal);
// Set the world space geometric normal.
sample.m_geometric_normal = triangle.m_geometric_normal;
// Compute the probability of choosing this sample.
// assert(feq(triangle_prob * triangle.m_rcp_area, m_rcp_total_emissive_area)); // subject to numerical instability
sample.m_probability = m_rcp_total_emissive_area;
}
