181 lines
8.6 KiB
C++
181 lines
8.6 KiB
C++
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// Copyright 2014 Citra Emulator Project
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// Licensed under GPLv2
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// Refer to the license.txt file included.
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#include <algorithm>
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#include "common/common_types.h"
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#include "math.h"
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#include "pica.h"
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#include "rasterizer.h"
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#include "vertex_shader.h"
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namespace Pica {
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namespace Rasterizer {
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static void DrawPixel(int x, int y, const Math::Vec4<u8>& color) {
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u32* color_buffer = (u32*)Memory::GetPointer(registers.framebuffer.GetColorBufferAddress());
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u32 value = (color.a() << 24) | (color.r() << 16) | (color.g() << 8) | color.b();
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// Assuming RGBA8 format until actual framebuffer format handling is implemented
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*(color_buffer + x + y * registers.framebuffer.GetWidth() / 2) = value;
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}
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static u32 GetDepth(int x, int y) {
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u16* depth_buffer = (u16*)Memory::GetPointer(registers.framebuffer.GetDepthBufferAddress());
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// Assuming 16-bit depth buffer format until actual format handling is implemented
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return *(depth_buffer + x + y * registers.framebuffer.GetWidth() / 2);
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}
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static void SetDepth(int x, int y, u16 value) {
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u16* depth_buffer = (u16*)Memory::GetPointer(registers.framebuffer.GetDepthBufferAddress());
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// Assuming 16-bit depth buffer format until actual format handling is implemented
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*(depth_buffer + x + y * registers.framebuffer.GetWidth() / 2) = value;
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}
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void ProcessTriangle(const VertexShader::OutputVertex& v0,
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const VertexShader::OutputVertex& v1,
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const VertexShader::OutputVertex& v2)
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{
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// NOTE: Assuming that rasterizer coordinates are 12.4 fixed-point values
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struct Fix12P4 {
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Fix12P4() {}
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Fix12P4(u16 val) : val(val) {}
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static u16 FracMask() { return 0xF; }
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static u16 IntMask() { return (u16)~0xF; }
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operator u16() const {
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return val;
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}
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bool operator < (const Fix12P4& oth) const {
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return (u16)*this < (u16)oth;
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}
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private:
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u16 val;
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};
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// vertex positions in rasterizer coordinates
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auto FloatToFix = [](float24 flt) {
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return Fix12P4(flt.ToFloat32() * 16.0f);
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};
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auto ScreenToRasterizerCoordinates = [FloatToFix](const Math::Vec3<float24> vec) {
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return Math::Vec3<Fix12P4>{FloatToFix(vec.x), FloatToFix(vec.y), FloatToFix(vec.z)};
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};
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Math::Vec3<Fix12P4> vtxpos[3]{ ScreenToRasterizerCoordinates(v0.screenpos),
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ScreenToRasterizerCoordinates(v1.screenpos),
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ScreenToRasterizerCoordinates(v2.screenpos) };
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// TODO: Proper scissor rect test!
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u16 min_x = std::min({vtxpos[0].x, vtxpos[1].x, vtxpos[2].x});
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u16 min_y = std::min({vtxpos[0].y, vtxpos[1].y, vtxpos[2].y});
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u16 max_x = std::max({vtxpos[0].x, vtxpos[1].x, vtxpos[2].x});
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u16 max_y = std::max({vtxpos[0].y, vtxpos[1].y, vtxpos[2].y});
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min_x = min_x & Fix12P4::IntMask();
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min_y = min_y & Fix12P4::IntMask();
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max_x = (max_x + Fix12P4::FracMask()) & Fix12P4::IntMask();
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max_y = (max_y + Fix12P4::FracMask()) & Fix12P4::IntMask();
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// Triangle filling rules: Pixels on the right-sided edge or on flat bottom edges are not
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// drawn. Pixels on any other triangle border are drawn. This is implemented with three bias
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// values which are added to the barycentric coordinates w0, w1 and w2, respectively.
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// NOTE: These are the PSP filling rules. Not sure if the 3DS uses the same ones...
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auto IsRightSideOrFlatBottomEdge = [](const Math::Vec2<Fix12P4>& vtx,
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const Math::Vec2<Fix12P4>& line1,
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const Math::Vec2<Fix12P4>& line2)
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{
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if (line1.y == line2.y) {
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// just check if vertex is above us => bottom line parallel to x-axis
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return vtx.y < line1.y;
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} else {
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// check if vertex is on our left => right side
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// TODO: Not sure how likely this is to overflow
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return (int)vtx.x < (int)line1.x + ((int)line2.x - (int)line1.x) * ((int)vtx.y - (int)line1.y) / ((int)line2.y - (int)line1.y);
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}
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};
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int bias0 = IsRightSideOrFlatBottomEdge(vtxpos[0].xy(), vtxpos[1].xy(), vtxpos[2].xy()) ? -1 : 0;
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int bias1 = IsRightSideOrFlatBottomEdge(vtxpos[1].xy(), vtxpos[2].xy(), vtxpos[0].xy()) ? -1 : 0;
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int bias2 = IsRightSideOrFlatBottomEdge(vtxpos[2].xy(), vtxpos[0].xy(), vtxpos[1].xy()) ? -1 : 0;
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// TODO: Not sure if looping through x first might be faster
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for (u16 y = min_y; y < max_y; y += 0x10) {
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for (u16 x = min_x; x < max_x; x += 0x10) {
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// Calculate the barycentric coordinates w0, w1 and w2
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auto orient2d = [](const Math::Vec2<Fix12P4>& vtx1,
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const Math::Vec2<Fix12P4>& vtx2,
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const Math::Vec2<Fix12P4>& vtx3) {
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const auto vec1 = (vtx2.Cast<int>() - vtx1.Cast<int>()).Append(0);
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const auto vec2 = (vtx3.Cast<int>() - vtx1.Cast<int>()).Append(0);
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// TODO: There is a very small chance this will overflow for sizeof(int) == 4
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return Cross(vec1, vec2).z;
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};
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int w0 = bias0 + orient2d(vtxpos[1].xy(), vtxpos[2].xy(), {x, y});
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int w1 = bias1 + orient2d(vtxpos[2].xy(), vtxpos[0].xy(), {x, y});
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int w2 = bias2 + orient2d(vtxpos[0].xy(), vtxpos[1].xy(), {x, y});
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int wsum = w0 + w1 + w2;
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// If current pixel is not covered by the current primitive
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if (w0 < 0 || w1 < 0 || w2 < 0)
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continue;
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// Perspective correct attribute interpolation:
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// Attribute values cannot be calculated by simple linear interpolation since
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// they are not linear in screen space. For example, when interpolating a
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// texture coordinate across two vertices, something simple like
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// u = (u0*w0 + u1*w1)/(w0+w1)
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// will not work. However, the attribute value divided by the
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// clipspace w-coordinate (u/w) and and the inverse w-coordinate (1/w) are linear
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// in screenspace. Hence, we can linearly interpolate these two independently and
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// calculate the interpolated attribute by dividing the results.
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// I.e.
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// u_over_w = ((u0/v0.pos.w)*w0 + (u1/v1.pos.w)*w1)/(w0+w1)
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// one_over_w = (( 1/v0.pos.w)*w0 + ( 1/v1.pos.w)*w1)/(w0+w1)
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// u = u_over_w / one_over_w
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//
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// The generalization to three vertices is straightforward in baricentric coordinates.
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auto GetInterpolatedAttribute = [&](float24 attr0, float24 attr1, float24 attr2) {
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auto attr_over_w = Math::MakeVec3(attr0 / v0.pos.w,
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attr1 / v1.pos.w,
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attr2 / v2.pos.w);
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auto w_inverse = Math::MakeVec3(float24::FromFloat32(1.f) / v0.pos.w,
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float24::FromFloat32(1.f) / v1.pos.w,
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float24::FromFloat32(1.f) / v2.pos.w);
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auto baricentric_coordinates = Math::MakeVec3(float24::FromFloat32(w0),
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float24::FromFloat32(w1),
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float24::FromFloat32(w2));
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float24 interpolated_attr_over_w = Math::Dot(attr_over_w, baricentric_coordinates);
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float24 interpolated_w_inverse = Math::Dot(w_inverse, baricentric_coordinates);
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return interpolated_attr_over_w / interpolated_w_inverse;
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};
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Math::Vec4<u8> primary_color{
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(u8)(GetInterpolatedAttribute(v0.color.r(), v1.color.r(), v2.color.r()).ToFloat32() * 255),
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(u8)(GetInterpolatedAttribute(v0.color.g(), v1.color.g(), v2.color.g()).ToFloat32() * 255),
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(u8)(GetInterpolatedAttribute(v0.color.b(), v1.color.b(), v2.color.b()).ToFloat32() * 255),
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(u8)(GetInterpolatedAttribute(v0.color.a(), v1.color.a(), v2.color.a()).ToFloat32() * 255)
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};
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u16 z = (u16)(((float)v0.screenpos[2].ToFloat32() * w0 +
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(float)v1.screenpos[2].ToFloat32() * w1 +
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(float)v2.screenpos[2].ToFloat32() * w2) * 65535.f / wsum); // TODO: Shouldn't need to multiply by 65536?
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SetDepth(x >> 4, y >> 4, z);
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DrawPixel(x >> 4, y >> 4, primary_color);
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}
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}
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}
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} // namespace Rasterizer
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} // namespace Pica
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