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+ | BVH Sah

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TheRedShip
2025-01-19 17:58:11 +01:00
parent 71df788350
commit 0ae411d8ea
6 changed files with 104 additions and 2703 deletions
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73
srcs/class/BVH.cpp
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@ -44,26 +44,85 @@ void BVH::updateBounds(std::vector<GPUTriangle> &primitives)
}
}
float BVH::evaluateSah(std::vector<GPUTriangle> &primitives, int axis, float pos)
{
AABB left_box(glm::vec3(1e30f), glm::vec3(-1e30f));
AABB right_box(glm::vec3(1e30f), glm::vec3(-1e30f));
int left_count = 0;
int right_count = 0;
for (unsigned int i = 0; i < _primitive_count; i++)
{
GPUTriangle triangle = primitives[_first_primitive + i];
glm::vec3 centroid = (triangle.position + triangle.vertex1 + triangle.vertex2) / 3.0f;
if (centroid[axis] < pos)
{
left_count++;
left_box.grow( triangle.position );
left_box.grow( triangle.vertex1 );
left_box.grow( triangle.vertex2 );
}
else
{
right_count++;
right_box.grow( triangle.position );
right_box.grow( triangle.vertex1 );
right_box.grow( triangle.vertex2 );
}
}
float cost = left_count * left_box.area() + right_count * right_box.area();
return (cost > 0 ? cost : 1e30f);
}
void BVH::subdivide(std::vector<GPUTriangle> &primitives)
{
if (_primitive_count <= 100)
if (_primitive_count <= 4)
return ;
glm::vec3 extent = _aabb.max - _aabb.min;
int axis = 0;
if (extent.y > extent.x) axis = 1;
if (extent.z > extent[axis]) axis = 2;
const int num_test_per_axis = 5;
float split_pos = _aabb.min[axis] + extent[axis] * 0.5f;
int best_axis = 0;
float best_pos = 0;
float best_cost = 1e30f;
for (int axis = 0; axis < 3; axis++)
{
float start_pos = _aabb.min[axis];
float end_pos = _aabb.max[axis];
for (int i = 0; i < num_test_per_axis; i++)
{
float split_t = (i + 1) / (num_test_per_axis + 1.0f);
float candidate_pos = start_pos + (end_pos - start_pos) * split_t;
float cost = evaluateSah(primitives, axis, candidate_pos);
if (cost < best_cost)
{
best_pos = candidate_pos;
best_axis = axis;
best_cost = cost;
}
}
}
int axis = best_axis;
float split_pos = best_pos;
int i = _first_primitive;
int j = _first_primitive + _primitive_count - 1;
while (i <= j)
{
glm::vec3 centroid = primitives[i].position + primitives[i].vertex1 + primitives[i].vertex2;
centroid /= 3.0f;
GPUTriangle triangle = primitives[i];
glm::vec3 centroid = (triangle.position + triangle.vertex1 + triangle.vertex2) / 3.0f;
if (centroid[axis] < split_pos)
i++;