From 94d742fe172ba933af321bfb0e02889b40d0c179 Mon Sep 17 00:00:00 2001 From: Tony Wasserka Date: Sun, 27 Jul 2014 18:02:35 +0200 Subject: Pica: Add basic rasterizer. --- src/video_core/rasterizer.cpp | 180 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 180 insertions(+) create mode 100644 src/video_core/rasterizer.cpp (limited to 'src/video_core/rasterizer.cpp') diff --git a/src/video_core/rasterizer.cpp b/src/video_core/rasterizer.cpp new file mode 100644 index 00000000..a7c1bab3 --- /dev/null +++ b/src/video_core/rasterizer.cpp @@ -0,0 +1,180 @@ +// Copyright 2014 Citra Emulator Project +// Licensed under GPLv2 +// Refer to the license.txt file included. + +#include + +#include "common/common_types.h" + +#include "math.h" +#include "pica.h" +#include "rasterizer.h" +#include "vertex_shader.h" + +namespace Pica { + +namespace Rasterizer { + +static void DrawPixel(int x, int y, const Math::Vec4& color) { + u32* color_buffer = (u32*)Memory::GetPointer(registers.framebuffer.GetColorBufferAddress()); + u32 value = (color.a() << 24) | (color.r() << 16) | (color.g() << 8) | color.b(); + + // Assuming RGBA8 format until actual framebuffer format handling is implemented + *(color_buffer + x + y * registers.framebuffer.GetWidth() / 2) = value; +} + +static u32 GetDepth(int x, int y) { + u16* depth_buffer = (u16*)Memory::GetPointer(registers.framebuffer.GetDepthBufferAddress()); + + // Assuming 16-bit depth buffer format until actual format handling is implemented + return *(depth_buffer + x + y * registers.framebuffer.GetWidth() / 2); +} + +static void SetDepth(int x, int y, u16 value) { + u16* depth_buffer = (u16*)Memory::GetPointer(registers.framebuffer.GetDepthBufferAddress()); + + // Assuming 16-bit depth buffer format until actual format handling is implemented + *(depth_buffer + x + y * registers.framebuffer.GetWidth() / 2) = value; +} + +void ProcessTriangle(const VertexShader::OutputVertex& v0, + const VertexShader::OutputVertex& v1, + const VertexShader::OutputVertex& v2) +{ + // NOTE: Assuming that rasterizer coordinates are 12.4 fixed-point values + struct Fix12P4 { + Fix12P4() {} + Fix12P4(u16 val) : val(val) {} + + static u16 FracMask() { return 0xF; } + static u16 IntMask() { return (u16)~0xF; } + + operator u16() const { + return val; + } + + bool operator < (const Fix12P4& oth) const { + return (u16)*this < (u16)oth; + } + + private: + u16 val; + }; + + // vertex positions in rasterizer coordinates + auto FloatToFix = [](float24 flt) { + return Fix12P4(flt.ToFloat32() * 16.0f); + }; + auto ScreenToRasterizerCoordinates = [FloatToFix](const Math::Vec3 vec) { + return Math::Vec3{FloatToFix(vec.x), FloatToFix(vec.y), FloatToFix(vec.z)}; + }; + Math::Vec3 vtxpos[3]{ ScreenToRasterizerCoordinates(v0.screenpos), + ScreenToRasterizerCoordinates(v1.screenpos), + ScreenToRasterizerCoordinates(v2.screenpos) }; + + // TODO: Proper scissor rect test! + u16 min_x = std::min({vtxpos[0].x, vtxpos[1].x, vtxpos[2].x}); + u16 min_y = std::min({vtxpos[0].y, vtxpos[1].y, vtxpos[2].y}); + u16 max_x = std::max({vtxpos[0].x, vtxpos[1].x, vtxpos[2].x}); + u16 max_y = std::max({vtxpos[0].y, vtxpos[1].y, vtxpos[2].y}); + + min_x = min_x & Fix12P4::IntMask(); + min_y = min_y & Fix12P4::IntMask(); + max_x = (max_x + Fix12P4::FracMask()) & Fix12P4::IntMask(); + max_y = (max_y + Fix12P4::FracMask()) & Fix12P4::IntMask(); + + // Triangle filling rules: Pixels on the right-sided edge or on flat bottom edges are not + // drawn. Pixels on any other triangle border are drawn. This is implemented with three bias + // values which are added to the barycentric coordinates w0, w1 and w2, respectively. + // NOTE: These are the PSP filling rules. Not sure if the 3DS uses the same ones... + auto IsRightSideOrFlatBottomEdge = [](const Math::Vec2& vtx, + const Math::Vec2& line1, + const Math::Vec2& line2) + { + if (line1.y == line2.y) { + // just check if vertex is above us => bottom line parallel to x-axis + return vtx.y < line1.y; + } else { + // check if vertex is on our left => right side + // TODO: Not sure how likely this is to overflow + 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); + } + }; + int bias0 = IsRightSideOrFlatBottomEdge(vtxpos[0].xy(), vtxpos[1].xy(), vtxpos[2].xy()) ? -1 : 0; + int bias1 = IsRightSideOrFlatBottomEdge(vtxpos[1].xy(), vtxpos[2].xy(), vtxpos[0].xy()) ? -1 : 0; + int bias2 = IsRightSideOrFlatBottomEdge(vtxpos[2].xy(), vtxpos[0].xy(), vtxpos[1].xy()) ? -1 : 0; + + // TODO: Not sure if looping through x first might be faster + for (u16 y = min_y; y < max_y; y += 0x10) { + for (u16 x = min_x; x < max_x; x += 0x10) { + + // Calculate the barycentric coordinates w0, w1 and w2 + auto orient2d = [](const Math::Vec2& vtx1, + const Math::Vec2& vtx2, + const Math::Vec2& vtx3) { + const auto vec1 = (vtx2.Cast() - vtx1.Cast()).Append(0); + const auto vec2 = (vtx3.Cast() - vtx1.Cast()).Append(0); + // TODO: There is a very small chance this will overflow for sizeof(int) == 4 + return Cross(vec1, vec2).z; + }; + + int w0 = bias0 + orient2d(vtxpos[1].xy(), vtxpos[2].xy(), {x, y}); + int w1 = bias1 + orient2d(vtxpos[2].xy(), vtxpos[0].xy(), {x, y}); + int w2 = bias2 + orient2d(vtxpos[0].xy(), vtxpos[1].xy(), {x, y}); + int wsum = w0 + w1 + w2; + + // If current pixel is not covered by the current primitive + if (w0 < 0 || w1 < 0 || w2 < 0) + continue; + + // Perspective correct attribute interpolation: + // Attribute values cannot be calculated by simple linear interpolation since + // they are not linear in screen space. For example, when interpolating a + // texture coordinate across two vertices, something simple like + // u = (u0*w0 + u1*w1)/(w0+w1) + // will not work. However, the attribute value divided by the + // clipspace w-coordinate (u/w) and and the inverse w-coordinate (1/w) are linear + // in screenspace. Hence, we can linearly interpolate these two independently and + // calculate the interpolated attribute by dividing the results. + // I.e. + // u_over_w = ((u0/v0.pos.w)*w0 + (u1/v1.pos.w)*w1)/(w0+w1) + // one_over_w = (( 1/v0.pos.w)*w0 + ( 1/v1.pos.w)*w1)/(w0+w1) + // u = u_over_w / one_over_w + // + // The generalization to three vertices is straightforward in baricentric coordinates. + auto GetInterpolatedAttribute = [&](float24 attr0, float24 attr1, float24 attr2) { + auto attr_over_w = Math::MakeVec3(attr0 / v0.pos.w, + attr1 / v1.pos.w, + attr2 / v2.pos.w); + auto w_inverse = Math::MakeVec3(float24::FromFloat32(1.f) / v0.pos.w, + float24::FromFloat32(1.f) / v1.pos.w, + float24::FromFloat32(1.f) / v2.pos.w); + auto baricentric_coordinates = Math::MakeVec3(float24::FromFloat32(w0), + float24::FromFloat32(w1), + float24::FromFloat32(w2)); + + float24 interpolated_attr_over_w = Math::Dot(attr_over_w, baricentric_coordinates); + float24 interpolated_w_inverse = Math::Dot(w_inverse, baricentric_coordinates); + return interpolated_attr_over_w / interpolated_w_inverse; + }; + + Math::Vec4 primary_color{ + (u8)(GetInterpolatedAttribute(v0.color.r(), v1.color.r(), v2.color.r()).ToFloat32() * 255), + (u8)(GetInterpolatedAttribute(v0.color.g(), v1.color.g(), v2.color.g()).ToFloat32() * 255), + (u8)(GetInterpolatedAttribute(v0.color.b(), v1.color.b(), v2.color.b()).ToFloat32() * 255), + (u8)(GetInterpolatedAttribute(v0.color.a(), v1.color.a(), v2.color.a()).ToFloat32() * 255) + }; + + u16 z = (u16)(((float)v0.screenpos[2].ToFloat32() * w0 + + (float)v1.screenpos[2].ToFloat32() * w1 + + (float)v2.screenpos[2].ToFloat32() * w2) * 65535.f / wsum); // TODO: Shouldn't need to multiply by 65536? + SetDepth(x >> 4, y >> 4, z); + + DrawPixel(x >> 4, y >> 4, primary_color); + } + } +} + +} // namespace Rasterizer + +} // namespace Pica -- cgit v1.2.3