// Copyright 2014 Citra Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.
#include <boost/container/static_vector.hpp>
#include "clipper.h"
#include "pica.h"
#include "rasterizer.h"
#include "vertex_shader.h"
namespace Pica {
namespace Clipper {
struct ClippingEdge {
public:
ClippingEdge(Math::Vec4<float24> coeffs,
Math::Vec4<float24> bias = Math::Vec4<float24>(float24::FromFloat32(0),
float24::FromFloat32(0),
float24::FromFloat32(0),
float24::FromFloat32(0)))
: coeffs(coeffs),
bias(bias)
{
}
bool IsInside(const OutputVertex& vertex) const {
return Math::Dot(vertex.pos + bias, coeffs) <= float24::FromFloat32(0);
}
bool IsOutSide(const OutputVertex& vertex) const {
return !IsInside(vertex);
}
OutputVertex GetIntersection(const OutputVertex& v0, const OutputVertex& v1) const {
float24 dp = Math::Dot(v0.pos + bias, coeffs);
float24 dp_prev = Math::Dot(v1.pos + bias, coeffs);
float24 factor = dp_prev / (dp_prev - dp);
return OutputVertex::Lerp(factor, v0, v1);
}
private:
float24 pos;
Math::Vec4<float24> coeffs;
Math::Vec4<float24> bias;
};
static void InitScreenCoordinates(OutputVertex& vtx)
{
struct {
float24 halfsize_x;
float24 offset_x;
float24 halfsize_y;
float24 offset_y;
float24 zscale;
float24 offset_z;
} viewport;
viewport.halfsize_x = float24::FromRawFloat24(registers.viewport_size_x);
viewport.halfsize_y = float24::FromRawFloat24(registers.viewport_size_y);
viewport.offset_x = float24::FromFloat32(static_cast<float>(registers.viewport_corner.x));
viewport.offset_y = float24::FromFloat32(static_cast<float>(registers.viewport_corner.y));
viewport.zscale = float24::FromRawFloat24(registers.viewport_depth_range);
viewport.offset_z = float24::FromRawFloat24(registers.viewport_depth_far_plane);
float24 inv_w = float24::FromFloat32(1.f) / vtx.pos.w;
vtx.color *= inv_w;
vtx.tc0 *= inv_w;
vtx.tc1 *= inv_w;
vtx.tc2 *= inv_w;
vtx.pos.w = inv_w;
vtx.screenpos[0] = (vtx.pos.x * inv_w + float24::FromFloat32(1.0)) * viewport.halfsize_x + viewport.offset_x;
vtx.screenpos[1] = (vtx.pos.y * inv_w + float24::FromFloat32(1.0)) * viewport.halfsize_y + viewport.offset_y;
vtx.screenpos[2] = viewport.offset_z + vtx.pos.z * inv_w * viewport.zscale;
}
void ProcessTriangle(OutputVertex &v0, OutputVertex &v1, OutputVertex &v2) {
using boost::container::static_vector;
// 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;
// NOTE: We clip against a w=epsilon plane to guarantee that the output has a positive w value.
// TODO: Not sure if this is a valid approach. Also should probably instead use the smallest
// epsilon possible within float24 accuracy.
static const float24 EPSILON = float24::FromFloat32(0.00001);
static const float24 f0 = float24::FromFloat32(0.0);
static const float24 f1 = float24::FromFloat32(1.0);
static const std::array<ClippingEdge, 7> clipping_edges = {{
{ Math::MakeVec( f1, f0, f0, -f1) }, // x = +w
{ Math::MakeVec(-f1, f0, f0, -f1) }, // x = -w
{ Math::MakeVec( f0, f1, f0, -f1) }, // y = +w
{ Math::MakeVec( f0, -f1, f0, -f1) }, // y = -w
{ Math::MakeVec( f0, f0, f1, f0) }, // z = 0
{ Math::MakeVec( f0, f0, -f1, -f1) }, // z = -w
{ Math::MakeVec( f0, f0, f0, -f1), Math::Vec4<float24>(f0, f0, f0, EPSILON) }, // w = EPSILON
}};
// TODO: If one vertex lies outside one of the depth clipping planes, some platforms (e.g. Wii)
// drop the whole primitive instead of clipping the primitive properly. We should test if
// this happens on the 3DS, too.
// Simple implementation of the Sutherland-Hodgman clipping algorithm.
// TODO: Make this less inefficient (currently lots of useless buffering overhead happens here)
for (auto edge : clipping_edges) {
std::swap(input_list, output_list);
output_list->clear();
const OutputVertex* reference_vertex = &input_list->back();
for (const auto& vertex : *input_list) {
// NOTE: This algorithm changes vertex order in some cases!
if (edge.IsInside(vertex)) {
if (edge.IsOutSide(*reference_vertex)) {
output_list->push_back(edge.GetIntersection(vertex, *reference_vertex));
}
output_list->push_back(vertex);
} else if (edge.IsInside(*reference_vertex)) {
output_list->push_back(edge.GetIntersection(vertex, *reference_vertex));
}
reference_vertex = &vertex;
}
// Need to have at least a full triangle to continue...
if (output_list->size() < 3)
return;
}
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];
InitScreenCoordinates(vtx2);
LOG_TRACE(Render_Software,
"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(),
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(),
vtx0.screenpos.x.ToFloat32(), vtx0.screenpos.y.ToFloat32(), vtx0.screenpos.z.ToFloat32(),
vtx1.screenpos.x.ToFloat32(), vtx1.screenpos.y.ToFloat32(), vtx1.screenpos.z.ToFloat32(),
vtx2.screenpos.x.ToFloat32(), vtx2.screenpos.y.ToFloat32(), vtx2.screenpos.z.ToFloat32());
Rasterizer::ProcessTriangle(vtx0, vtx1, vtx2);
}
}
} // namespace
} // namespace
