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Pica: Cleanup clipping code and change screenspace z to range from -1..0.

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The change in depth range seems to reflect better to what applications are expecting, and makes for cleaner code overall (hence is more likely to reflect hardware behavior).
pull/8/head
Tony Wasserka 10 years ago
parent 70a764d992
commit 365236fa4c
2 changed files with 42 additions and 53 deletions
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84
src/video_core/clipper.cpp
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@ -15,30 +15,18 @@ namespace Clipper {
struct ClippingEdge { struct ClippingEdge {
public: public:
enum Type { ClippingEdge(Math::Vec4<float24> coeffs,
POS_X = 0, Math::Vec4<float24> bias = Math::Vec4<float24>(float24::FromFloat32(0),
NEG_X = 1, float24::FromFloat32(0),
POS_Y = 2, float24::FromFloat32(0),
NEG_Y = 3, float24::FromFloat32(0)))
POS_Z = 4, : coeffs(coeffs),
NEG_Z = 5, bias(bias)
}; {
}
ClippingEdge(Type type, float24 position) : type(type), pos(position) {}
bool IsInside(const OutputVertex& vertex) const { bool IsInside(const OutputVertex& vertex) const {
switch (type) { return Math::Dot(vertex.pos + bias, coeffs) <= float24::FromFloat32(0);
case POS_X: return vertex.pos.x <= pos * vertex.pos.w;
case NEG_X: return vertex.pos.x >= pos * vertex.pos.w;
case POS_Y: return vertex.pos.y <= pos * vertex.pos.w;
case NEG_Y: return vertex.pos.y >= pos * vertex.pos.w;
// TODO: Check z compares ... should be 0..1 instead?
case POS_Z: return vertex.pos.z <= pos * vertex.pos.w;
default:
case NEG_Z: return vertex.pos.z >= pos * vertex.pos.w;
}
} }
bool IsOutSide(const OutputVertex& vertex) const { bool IsOutSide(const OutputVertex& vertex) const {
@ -46,31 +34,17 @@ public:
} }
OutputVertex GetIntersection(const OutputVertex& v0, const OutputVertex& v1) const { OutputVertex GetIntersection(const OutputVertex& v0, const OutputVertex& v1) const {
auto dotpr = [this](const OutputVertex& vtx) { float24 dp = Math::Dot(v0.pos + bias, coeffs);
switch (type) { float24 dp_prev = Math::Dot(v1.pos + bias, coeffs);
case POS_X: return vtx.pos.x - vtx.pos.w;
case NEG_X: return -vtx.pos.x - vtx.pos.w;
case POS_Y: return vtx.pos.y - vtx.pos.w;
case NEG_Y: return -vtx.pos.y - vtx.pos.w;
// TODO: Verify z clipping
case POS_Z: return vtx.pos.z - vtx.pos.w;
default:
case NEG_Z: return -vtx.pos.w;
}
};
float24 dp = dotpr(v0);
float24 dp_prev = dotpr(v1);
float24 factor = dp_prev / (dp_prev - dp); float24 factor = dp_prev / (dp_prev - dp);
return OutputVertex::Lerp(factor, v0, v1); return OutputVertex::Lerp(factor, v0, v1);
} }
private: private:
Type type;
float24 pos; float24 pos;
Math::Vec4<float24> coeffs;
Math::Vec4<float24> bias;
}; };
static void InitScreenCoordinates(OutputVertex& vtx) static void InitScreenCoordinates(OutputVertex& vtx)
@ -98,10 +72,9 @@ static void InitScreenCoordinates(OutputVertex& vtx)
vtx.tc2 *= inv_w; vtx.tc2 *= inv_w;
vtx.pos.w = inv_w; vtx.pos.w = inv_w;
// TODO: Not sure why the viewport width needs to be divided by 2 but the viewport height does not
vtx.screenpos[0] = (vtx.pos.x * inv_w + float24::FromFloat32(1.0)) * viewport.halfsize_x + viewport.offset_x; 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[1] = (vtx.pos.y * inv_w + float24::FromFloat32(1.0)) * viewport.halfsize_y + viewport.offset_y;
vtx.screenpos[2] = viewport.offset_z - vtx.pos.z * inv_w * viewport.zscale; vtx.screenpos[2] = viewport.offset_z + vtx.pos.z * inv_w * viewport.zscale;
} }
void ProcessTriangle(OutputVertex &v0, OutputVertex &v1, OutputVertex &v2) { void ProcessTriangle(OutputVertex &v0, OutputVertex &v1, OutputVertex &v2) {
@ -117,14 +90,29 @@ void ProcessTriangle(OutputVertex &v0, OutputVertex &v1, OutputVertex &v2) {
auto* output_list = &buffer_a; auto* output_list = &buffer_a;
auto* input_list = &buffer_b; 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(0.00001);
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. // Simple implementation of the Sutherland-Hodgman clipping algorithm.
// TODO: Make this less inefficient (currently lots of useless buffering overhead happens here) // TODO: Make this less inefficient (currently lots of useless buffering overhead happens here)
for (auto edge : { ClippingEdge(ClippingEdge::POS_X, float24::FromFloat32(+1.0)), for (auto edge : clipping_edges) {
ClippingEdge(ClippingEdge::NEG_X, float24::FromFloat32(-1.0)),
ClippingEdge(ClippingEdge::POS_Y, float24::FromFloat32(+1.0)),
ClippingEdge(ClippingEdge::NEG_Y, float24::FromFloat32(-1.0)),
ClippingEdge(ClippingEdge::POS_Z, float24::FromFloat32(+1.0)),
ClippingEdge(ClippingEdge::NEG_Z, float24::FromFloat32(-1.0)) }) {
std::swap(input_list, output_list); std::swap(input_list, output_list);
output_list->clear(); output_list->clear();

11
src/video_core/rasterizer.cpp
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@ -106,16 +106,17 @@ void ProcessTriangle(const VertexShader::OutputVertex& v0,
ScreenToRasterizerCoordinates(v1.screenpos), ScreenToRasterizerCoordinates(v1.screenpos),
ScreenToRasterizerCoordinates(v2.screenpos) }; ScreenToRasterizerCoordinates(v2.screenpos) };
if (registers.cull_mode == Regs::CullMode::KeepClockWise) { if (registers.cull_mode == Regs::CullMode::KeepCounterClockWise) {
// Reverse vertex order and use the CCW code path. // Reverse vertex order and use the CW code path.
std::swap(vtxpos[1], vtxpos[2]); std::swap(vtxpos[1], vtxpos[2]);
} }
if (registers.cull_mode != Regs::CullMode::KeepAll) { if (registers.cull_mode != Regs::CullMode::KeepAll) {
// Cull away triangles which are wound clockwise. // Cull away triangles which are wound counter-clockwise.
// TODO: A check for degenerate triangles ("== 0") should be considered for CullMode::KeepAll
if (SignedArea(vtxpos[0].xy(), vtxpos[1].xy(), vtxpos[2].xy()) <= 0) if (SignedArea(vtxpos[0].xy(), vtxpos[1].xy(), vtxpos[2].xy()) <= 0)
return; return;
} else {
// TODO: Consider A check for degenerate triangles ("SignedArea == 0")
} }
// TODO: Proper scissor rect test! // TODO: Proper scissor rect test!
@ -475,7 +476,7 @@ void ProcessTriangle(const VertexShader::OutputVertex& v0,
// TODO: Does depth indeed only get written even if depth testing is enabled? // TODO: Does depth indeed only get written even if depth testing is enabled?
if (registers.output_merger.depth_test_enable) { if (registers.output_merger.depth_test_enable) {
u16 z = (u16)(-(v0.screenpos[2].ToFloat32() * w0 + u16 z = (u16)((v0.screenpos[2].ToFloat32() * w0 +
v1.screenpos[2].ToFloat32() * w1 + v1.screenpos[2].ToFloat32() * w1 +
v2.screenpos[2].ToFloat32() * w2) * 65535.f / wsum); v2.screenpos[2].ToFloat32() * w2) * 65535.f / wsum);
u16 ref_z = GetDepth(x >> 4, y >> 4); u16 ref_z = GetDepth(x >> 4, y >> 4);

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