1 files changed, 178 insertions, 0 deletions
diff --git a/src/video_core/swrasterizer/clipper.cpp b/src/video_core/swrasterizer/clipper.cpp
new file mode 100644
index 000000000..2d80822d9
--- /dev/null
+++ b/src/video_core/swrasterizer/clipper.cpp
@@ -0,0 +1,178 @@
+// 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.color *= inv_w;
+    vtx.view *= inv_w;
+    vtx.quat *= 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] = 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* 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
+    }};
+
+    // 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 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;
+        }
+
+        // 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++) {
+        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