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Tighter shadow culling - fix light colinear to frustum edge

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In rare situations if a light is placed near colinear to a frustum edge, the extra culling plane derived can have an inaccurate normal due to floating point error.
This PR detects colinear triangles, and prevents adding a culling plane in this situation.
This commit is contained in:
lawnjelly 2024-03-20 14:11:36 +00:00
parent fe01776f05
commit 70cd25f3eb
2 changed files with 45 additions and 6 deletions
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18
servers/rendering/rendering_light_culler.cpp
View file

@ -427,15 +427,19 @@ bool RenderingLightCuller::_add_light_camera_planes(LightCullPlanes &r_cull_plan
uint8_t *entry = &data.LUT_entries[lookup][0];
int n_edges = data.LUT_entry_sizes[lookup] - 1;
const Vector3 &pt2 = p_light_source.pos;
for (int e = 0; e < n_edges; e++) {
int i0 = entry[e];
int i1 = entry[e + 1];
const Vector3 &pt0 = data.frustum_points[i0];
const Vector3 &pt1 = data.frustum_points[i1];
// Create plane from 3 points.
Plane p(pt0, pt1, p_light_source.pos);
r_cull_planes.add_cull_plane(p);
if (!_is_colinear_tri(pt0, pt1, pt2)) {
// Create plane from 3 points.
Plane p(pt0, pt1, pt2);
r_cull_planes.add_cull_plane(p);
}
}
// Last to 0 edge.
@ -446,9 +450,11 @@ bool RenderingLightCuller::_add_light_camera_planes(LightCullPlanes &r_cull_plan
const Vector3 &pt0 = data.frustum_points[i0];
const Vector3 &pt1 = data.frustum_points[i1];
// Create plane from 3 points.
Plane p(pt0, pt1, p_light_source.pos);
r_cull_planes.add_cull_plane(p);
if (!_is_colinear_tri(pt0, pt1, pt2)) {
// Create plane from 3 points.
Plane p(pt0, pt1, pt2);
r_cull_planes.add_cull_plane(p);
}
}
#ifdef LIGHT_CULLER_DEBUG_LOGGING

33
servers/rendering/rendering_light_culler.h
View file

@ -163,6 +163,39 @@ private:
bool _prepare_light(const RendererSceneCull::Instance &p_instance, int32_t p_directional_light_id = -1);
// Avoid adding extra culling planes derived from near colinear triangles.
// The normals derived from these will be inaccurate, and can lead to false
// culling of objects that should be within the light volume.
bool _is_colinear_tri(const Vector3 &p_a, const Vector3 &p_b, const Vector3 &p_c) const {
// Lengths of sides a, b and c.
float la = (p_b - p_a).length();
float lb = (p_c - p_b).length();
float lc = (p_c - p_a).length();
// Get longest side into lc.
if (lb < la) {
SWAP(la, lb);
}
if (lc < lb) {
SWAP(lb, lc);
}
// Prevent divide by zero.
if (lc > 0.00001f) {
// If the summed length of the smaller two
// sides is close to the length of the longest side,
// the points are colinear, and the triangle is near degenerate.
float ld = ((la + lb) - lc) / lc;
// ld will be close to zero for colinear tris.
return ld < 0.00001f;
}
// Don't create planes from tiny triangles,
// they won't be accurate.
return true;
}
// Internal version uses LightSource.
bool _add_light_camera_planes(LightCullPlanes &r_cull_planes, const LightSource &p_light_source);