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Fix #119692: Cycles render issue with light tree and light linking 

When using light linking with the light tree, the root index of a
mesh light subtree can be 0. The current code assumed this wasn't
possible, and as such it caused rendering issues, specifically the
incorrect computation of the PDF of certain mesh lights during
forward path tracing.

So we adjust the code to allow mesh light subtree root node
indices of 0.

This was worked on by Alaska, Sergey, and Weizhen

Pull Request: https://projects.blender.org/blender/blender/pulls/119770
This commit is contained in:
Alaska 2024-03-25 14:47:18 +01:00 committed by Brecht Van Lommel
parent aede88be85
commit 43cef92f66
1 changed files with 9 additions and 8 deletions
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17
intern/cycles/kernel/light/tree.h
View File

@ -796,7 +796,7 @@ ccl_device float light_tree_pdf(KernelGlobals kg,
ccl_global const KernelLightTreeEmitter *kemitter = &kernel_data_fetch(light_tree_emitters,
index_emitter);
int root_index;
int subtree_root_index;
uint bit_trail, target_emitter;
if (is_triangle(kemitter)) {
@ -805,16 +805,17 @@ ccl_device float light_tree_pdf(KernelGlobals kg,
target_emitter = kernel_data_fetch(object_to_tree, object_emitter);
ccl_global const KernelLightTreeEmitter *kmesh = &kernel_data_fetch(light_tree_emitters,
target_emitter);
root_index = kmesh->mesh.node_id;
ccl_global const KernelLightTreeNode *kroot = &kernel_data_fetch(light_tree_nodes, root_index);
subtree_root_index = kmesh->mesh.node_id;
ccl_global const KernelLightTreeNode *kroot = &kernel_data_fetch(light_tree_nodes,
subtree_root_index);
bit_trail = kroot->bit_trail;
if (kroot->type == LIGHT_TREE_INSTANCE) {
root_index = kroot->instance.reference;
subtree_root_index = kroot->instance.reference;
}
}
else {
root_index = 0;
subtree_root_index = -1;
bit_trail = kemitter->bit_trail;
target_emitter = index_emitter;
}
@ -856,13 +857,13 @@ ccl_device float light_tree_pdf(KernelGlobals kg,
return 0.0f;
}
if (root_index) {
if (subtree_root_index != -1) {
/* Arrived at the mesh light. Continue with the subtree. */
float unused;
light_tree_to_local_space<false>(kg, object_emitter, P, N, unused);
node_index = root_index;
root_index = 0;
node_index = subtree_root_index;
subtree_root_index = -1;
target_emitter = index_emitter;
bit_trail = kemitter->bit_trail;
continue;