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// Copyright 2014 Citra Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.
#include <algorithm>
#include <array>
#include <cstddef>
#include <boost/container/static_vector.hpp>
#include <boost/container/vector.hpp>
#include "common/bit_field.h"
#include "common/common_types.h"
#include "common/logging/log.h"
#include "common/vector_math.h"
#include "video_core/pica_state.h"
#include "video_core/pica_types.h"
#include "video_core/shader/shader.h"
#include "video_core/swrasterizer/clipper.h"
#include "video_core/swrasterizer/rasterizer.h"
using Pica::Rasterizer::Vertex;
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 Vertex& vertex) const {
return Math::Dot(vertex.pos + bias, coeffs) <= float24::FromFloat32(0);
}
bool IsOutSide(const Vertex& vertex) const {
return !IsInside(vertex);
}
Vertex GetIntersection(const Vertex& v0, const Vertex& 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 Vertex::Lerp(factor, v0, v1);
}
private:
float24 pos;
Math::Vec4<float24> coeffs;
Math::Vec4<float24> bias;
};
static void InitScreenCoordinates(Vertex& vtx) {
struct {
float24 halfsize_x;
float24 offset_x;
float24 halfsize_y;
float24 offset_y;
float24 zscale;
float24 offset_z;
} viewport;
const auto& regs = g_state.regs;
viewport.halfsize_x = float24::FromRaw(regs.rasterizer.viewport_size_x);
viewport.halfsize_y = float24::FromRaw(regs.rasterizer.viewport_size_y);
viewport.offset_x = float24::FromFloat32(static_cast<float>(regs.rasterizer.viewport_corner.x));
viewport.offset_y = float24::FromFloat32(static_cast<float>(regs.rasterizer.viewport_corner.y));
float24 inv_w = float24::FromFloat32(1.f) / vtx.pos.w;
vtx.pos.w = inv_w;
vtx.quat *= inv_w;
vtx.color *= inv_w;
vtx.tc0 *= inv_w;
vtx.tc1 *= inv_w;
vtx.tc0_w *= inv_w;
vtx.view *= inv_w;
vtx.tc2 *= 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] = vtx.pos.z * inv_w;
}
void ProcessTriangle(const OutputVertex& v0, const OutputVertex& v1, const 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<Vertex, MAX_VERTICES> buffer_a = {v0, v1, v2};
static_vector<Vertex, MAX_VERTICES> buffer_b;
auto FlipQuaternionIfOpposite = [](auto& a, const auto& b) {
if (Math::Dot(a, b) < float24::Zero())
a = -a;
};
// Flip the quaternions if they are opposite to prevent interpolating them over the wrong
// direction.
FlipQuaternionIfOpposite(buffer_a[1].quat, buffer_a[0].quat);
FlipQuaternionIfOpposite(buffer_a[2].quat, buffer_a[0].quat);
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(0.00001f);
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
}};
// Simple implementation of the Sutherland-Hodgman clipping algorithm.
// TODO: Make this less inefficient (currently lots of useless buffering overhead happens here)
auto Clip = [&](const ClippingEdge& edge) {
std::swap(input_list, output_list);
output_list->clear();
const Vertex* 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;
}
};
for (auto edge : clipping_edges) {
Clip(edge);
// Need to have at least a full triangle to continue...
if (output_list->size() < 3)
return;
}
if (g_state.regs.rasterizer.clip_enable) {
ClippingEdge custom_edge{-g_state.regs.rasterizer.GetClipCoef()};
Clip(custom_edge);
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++) {
Vertex& vtx0 = (*output_list)[0];
Vertex& vtx1 = (*output_list)[i + 1];
Vertex& 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 + 1, output_list->size() - 2, 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
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