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Cycles: SVM optimization for mix shaders, to skip more code when the mix weight

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for one of the input shaders is zero.

This gives about 5% speedup for koro_final.blend. In general this is important
so you can design shaders that run faster for shadows, diffuse bounces, etc, for
example by skipping procedural textures or even using a single fixed color.
This commit is contained in:
Brecht Van Lommel
2014-04-18 13:40:30 +02:00
parent 2d7b53331c
commit 2a9ef256b1
3 changed files with 72 additions and 12 deletions
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72
intern/cycles/render/svm.cpp
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@@ -515,11 +515,6 @@ void SVMCompiler::generate_closure(ShaderNode *node, set<ShaderNode*>& done)
void SVMCompiler::generate_multi_closure(ShaderNode *node, set<ShaderNode*>& done, set<ShaderNode*>& closure_done)
{
/* todo: the weak point here is that unlike the single closure sampling
* we will evaluate all nodes even if they are used as input for closures
* that are unused. it's not clear what would be the best way to skip such
* nodes at runtime, especially if they are tangled up */
/* only generate once */
if(closure_done.find(node) != closure_done.end())
return;
@@ -530,11 +525,70 @@ void SVMCompiler::generate_multi_closure(ShaderNode *node, set<ShaderNode*>& don
/* weighting is already taken care of in ShaderGraph::transform_multi_closure */
ShaderInput *cl1in = node->input("Closure1");
ShaderInput *cl2in = node->input("Closure2");
ShaderInput *facin = node->input("Fac");
if(cl1in->link)
generate_multi_closure(cl1in->link->parent, done, closure_done);
if(cl2in->link)
generate_multi_closure(cl2in->link->parent, done, closure_done);
/* skip empty mix/add closure nodes */
if(!cl1in->link && !cl2in->link)
return;
if(facin && facin->link) {
/* mix closure: generate instructions to compute mix weight */
set<ShaderNode*> dependencies;
find_dependencies(dependencies, done, facin);
generate_svm_nodes(dependencies, done);
stack_assign(facin); /* XXX unassign? */
/* execute shared dependencies. this is needed to allow skipping
* of zero weight closures and their dependencies later, so we
* ensure that they only skip dependencies that are unique to them */
set<ShaderNode*> cl1deps, cl2deps, shareddeps;
find_dependencies(cl1deps, done, cl1in);
find_dependencies(cl2deps, done, cl2in);
set_intersection(cl1deps.begin(), cl1deps.end(),
cl2deps.begin(), cl2deps.end(),
std::inserter(shareddeps, shareddeps.begin()));
generate_svm_nodes(shareddeps, done);
/* generate instructions for input closure 1 */
if(cl1in->link) {
/* add instruction to skip closure and its dependencies if mix weight is zero */
svm_nodes.push_back(make_int4(NODE_JUMP_IF_ONE, 0, facin->stack_offset, 0));
int node_jump_skip_index = svm_nodes.size() - 1;
generate_multi_closure(cl1in->link->parent, done, closure_done);
/* fill in jump instruction location to be after closure */
svm_nodes[node_jump_skip_index].y = svm_nodes.size() - node_jump_skip_index - 1;
}
/* generate instructions for input closure 2 */
if(cl2in->link) {
/* add instruction to skip closure and its dependencies if mix weight is zero */
svm_nodes.push_back(make_int4(NODE_JUMP_IF_ZERO, 0, facin->stack_offset, 0));
int node_jump_skip_index = svm_nodes.size() - 1;
generate_multi_closure(cl2in->link->parent, done, closure_done);
/* fill in jump instruction location to be after closure */
svm_nodes[node_jump_skip_index].y = svm_nodes.size() - node_jump_skip_index - 1;
}
/* unassign */
facin->stack_offset = SVM_STACK_INVALID; // XXX clear?
}
else {
/* execute closures and their dependencies, no runtime checks
* to skip closures here because was already optimized due to
* fixed weight or add closure that always needs both */
if(cl1in->link)
generate_multi_closure(cl1in->link->parent, done, closure_done);
if(cl2in->link)
generate_multi_closure(cl2in->link->parent, done, closure_done);
}
}
else {
/* execute dependencies for closure */