From 7e9bc85cc826c55a5aa612a3c2f14b8fb631a68c Mon Sep 17 00:00:00 2001
From: Yuri Kunde Schlesner <yuriks@yuriks.net>
Date: Sun, 28 Dec 2014 23:05:15 -0200
Subject: [PATCH] Clipper: Compact buffers on each clipping pass
Use a new buffer management scheme in the clipper that allows using a
bounded minimal amount of buffer space. Even though it copies more data
it is still slightly faster likely due to using less cache.
---
src/video_core/clipper.cpp | 55 +++++++++++++++++++-------------------
1 file changed, 27 insertions(+), 28 deletions(-)
diff --git a/src/video_core/clipper.cpp b/src/video_core/clipper.cpp
index e89b7a0c0e..0521ef8661 100644
--- a/src/video_core/clipper.cpp
+++ b/src/video_core/clipper.cpp
@@ -100,13 +100,15 @@ static void InitScreenCoordinates(OutputVertex& vtx)
void ProcessTriangle(OutputVertex &v0, OutputVertex &v1, OutputVertex &v2) {
using boost::container::static_vector;
- // TODO (neobrain):
- // The list of output vertices has some fixed maximum size,
- // however I haven't taken the time to figure out what it is exactly.
- // For now, we hence just assume a maximal size of 256 vertices.
- static const size_t MAX_VERTICES = 256;
- static_vector<OutputVertex, MAX_VERTICES> buffer_vertices;
- static_vector<OutputVertex*, MAX_VERTICES> output_list = { &v0, &v1, &v2 };
+ // Clipping a planar n-gon against a plane will remove at least 1 vertex and introduces 2 at
+ // the new edge (or less in degenerate cases). As such, we can say that each clipping plane
+ // introduces at most 1 new vertex to the polygon. Since we start with a triangle and have a
+ // fixed 6 clipping planes, the maximum number of vertices of the clipped polygon is 3 + 6 = 9.
+ static const size_t MAX_VERTICES = 9;
+ static_vector<OutputVertex, MAX_VERTICES> buffer_a = { v0, v1, v2 };
+ static_vector<OutputVertex, MAX_VERTICES> buffer_b;
+ auto* output_list = &buffer_a;
+ auto* input_list = &buffer_b;
// Simple implementation of the Sutherland-Hodgman clipping algorithm.
// TODO: Make this less inefficient (currently lots of useless buffering overhead happens here)
@@ -117,48 +119,45 @@ void ProcessTriangle(OutputVertex &v0, OutputVertex &v1, OutputVertex &v2) {
ClippingEdge(ClippingEdge::POS_Z, float24::FromFloat32(+1.0)),
ClippingEdge(ClippingEdge::NEG_Z, float24::FromFloat32(-1.0)) }) {
- const static_vector<OutputVertex*, MAX_VERTICES> input_list = output_list;
- output_list.clear();
+ std::swap(input_list, output_list);
+ output_list->clear();
- const OutputVertex* reference_vertex = input_list.back();
+ const OutputVertex* reference_vertex = &input_list->back();
- for (const auto& vertex : input_list) {
+ for (const auto& vertex : *input_list) {
// NOTE: This algorithm changes vertex order in some cases!
- if (edge.IsInside(*vertex)) {
+ if (edge.IsInside(vertex)) {
if (edge.IsOutSide(*reference_vertex)) {
- buffer_vertices.push_back(edge.GetIntersection(*vertex, *reference_vertex));
- output_list.push_back(&(buffer_vertices.back()));
+ output_list->push_back(edge.GetIntersection(vertex, *reference_vertex));
}
- output_list.push_back(vertex);
+ output_list->push_back(vertex);
} else if (edge.IsInside(*reference_vertex)) {
- buffer_vertices.push_back(edge.GetIntersection(*vertex, *reference_vertex));
- output_list.push_back(&(buffer_vertices.back()));
+ output_list->push_back(edge.GetIntersection(vertex, *reference_vertex));
}
-
- reference_vertex = vertex;
+ reference_vertex = &vertex;
}
// Need to have at least a full triangle to continue...
- if (output_list.size() < 3)
+ if (output_list->size() < 3)
return;
}
- InitScreenCoordinates(*(output_list[0]));
- InitScreenCoordinates(*(output_list[1]));
+ InitScreenCoordinates((*output_list)[0]);
+ InitScreenCoordinates((*output_list)[1]);
- for (size_t i = 0; i < output_list.size() - 2; i ++) {
- OutputVertex& vtx0 = *(output_list[0]);
- OutputVertex& vtx1 = *(output_list[i+1]);
- OutputVertex& vtx2 = *(output_list[i+2]);
+ for (size_t i = 0; i < output_list->size() - 2; i ++) {
+ OutputVertex& vtx0 = (*output_list)[0];
+ OutputVertex& vtx1 = (*output_list)[i+1];
+ OutputVertex& vtx2 = (*output_list)[i+2];
InitScreenCoordinates(vtx2);
LOG_TRACE(Render_Software,
- "Triangle %lu/%lu (%lu buffer vertices) at position (%.3f, %.3f, %.3f, %.3f), "
+ "Triangle %lu/%lu at position (%.3f, %.3f, %.3f, %.3f), "
"(%.3f, %.3f, %.3f, %.3f), (%.3f, %.3f, %.3f, %.3f) and "
"screen position (%.2f, %.2f, %.2f), (%.2f, %.2f, %.2f), (%.2f, %.2f, %.2f)",
- i,output_list.size(), buffer_vertices.size(),
+ i, output_list->size(),
vtx0.pos.x.ToFloat32(), vtx0.pos.y.ToFloat32(), vtx0.pos.z.ToFloat32(), vtx0.pos.w.ToFloat32(),
vtx1.pos.x.ToFloat32(), vtx1.pos.y.ToFloat32(), vtx1.pos.z.ToFloat32(), vtx1.pos.w.ToFloat32(),
vtx2.pos.x.ToFloat32(), vtx2.pos.y.ToFloat32(), vtx2.pos.z.ToFloat32(), vtx2.pos.w.ToFloat32(),