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Pica/Rasterizer: Implement backface culling.

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This commit is contained in:
Tony Wasserka 2014-12-13 21:39:42 +01:00
parent 3b78af904e
commit 0f49424022
2 changed files with 36 additions and 10 deletions
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16
src/video_core/pica.h
View File

@ -50,7 +50,19 @@ struct Regs {
u32 trigger_irq;
INSERT_PADDING_WORDS(0x30);
INSERT_PADDING_WORDS(0x2f);
enum class CullMode : u32 {
// Select which polygons are considered to be "frontfacing".
KeepAll = 0,
KeepClockWise = 1,
KeepCounterClockWise = 2,
// TODO: What does the third value imply?
};
union {
BitField<0, 2, CullMode> cull_mode;
};
BitField<0, 24, u32> viewport_size_x;
@ -659,6 +671,7 @@ struct Regs {
} while(false)
ADD_FIELD(trigger_irq);
ADD_FIELD(cull_mode);
ADD_FIELD(viewport_size_x);
ADD_FIELD(viewport_size_y);
ADD_FIELD(viewport_depth_range);
@ -730,6 +743,7 @@ private:
#define ASSERT_REG_POSITION(field_name, position) static_assert(offsetof(Regs, field_name) == position * 4, "Field "#field_name" has invalid position")
ASSERT_REG_POSITION(trigger_irq, 0x10);
ASSERT_REG_POSITION(cull_mode, 0x40);
ASSERT_REG_POSITION(viewport_size_x, 0x41);
ASSERT_REG_POSITION(viewport_size_y, 0x43);
ASSERT_REG_POSITION(viewport_depth_range, 0x4d);

30
src/video_core/rasterizer.cpp
View File

@ -82,10 +82,31 @@ void ProcessTriangle(const VertexShader::OutputVertex& v0,
auto ScreenToRasterizerCoordinates = [FloatToFix](const Math::Vec3<float24> vec) {
return Math::Vec3<Fix12P4>{FloatToFix(vec.x), FloatToFix(vec.y), FloatToFix(vec.z)};
};
static auto orient2d = [](const Math::Vec2<Fix12P4>& vtx1,
const Math::Vec2<Fix12P4>& vtx2,
const Math::Vec2<Fix12P4>& vtx3) {
const auto vec1 = Math::MakeVec(vtx2 - vtx1, 0);
const auto vec2 = Math::MakeVec(vtx3 - vtx1, 0);
// TODO: There is a very small chance this will overflow for sizeof(int) == 4
return Math::Cross(vec1, vec2).z;
};
Math::Vec3<Fix12P4> vtxpos[3]{ ScreenToRasterizerCoordinates(v0.screenpos),
ScreenToRasterizerCoordinates(v1.screenpos),
ScreenToRasterizerCoordinates(v2.screenpos) };
if (registers.cull_mode == Regs::CullMode::KeepClockWise) {
// Reverse vertex order and use the CCW code path.
std::swap(vtxpos[1], vtxpos[2]);
}
if (registers.cull_mode != Regs::CullMode::KeepAll) {
// Cull away triangles which are wound clockwise.
// TODO: A check for degenerate triangles ("== 0") should be considered for CullMode::KeepAll
if (orient2d(vtxpos[0].xy(), vtxpos[1].xy(), vtxpos[2].xy()) <= 0)
return;
}
// 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});
@ -128,15 +149,6 @@ void ProcessTriangle(const VertexShader::OutputVertex& v0,
for (u16 x = min_x; x < max_x; x += 0x10) {
// Calculate the barycentric coordinates w0, w1 and w2
auto orient2d = [](const Math::Vec2<Fix12P4>& vtx1,
const Math::Vec2<Fix12P4>& vtx2,
const Math::Vec2<Fix12P4>& vtx3) {
const auto vec1 = Math::MakeVec(vtx2 - vtx1, 0);
const auto vec2 = Math::MakeVec(vtx3 - vtx1, 0);
// TODO: There is a very small chance this will overflow for sizeof(int) == 4
return Math::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});