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fix(gs): correct depth write for all AFAIL alpha-fail modes #188

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fix(gs): correct depth write for all AFAIL alpha-fail modes #188

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21 changes: 13 additions & 8 deletions ps2xRuntime/src/lib/ps2_gs_rasterizer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -136,25 +136,27 @@ namespace
{
bool writeFramebuffer;
bool preserveDestinationAlpha;
bool writeDepth;
};

AlphaTestResult classifyAlphaTest(uint64_t testReg, uint8_t alpha)
{
const bool pass = passesAlphaTest(testReg, alpha);
if (pass)
return {true, false};
return {true, false, true};

// TEST.AFAIL controls what happens when the alpha comparison fails.
switch (static_cast<uint8_t>((testReg >> 12) & 0x3u))
{
case 1: // FB_ONLY
return {true, false};
return {true, false, false};
case 2: // ZB_ONLY
return {false, false, true};
case 3: // RGB_ONLY
return {true, true};
return {true, true, false};
case 0: // KEEP
case 2: // ZB_ONLY
default:
return {false, false};
return {false, false, false};
}
}

Expand Down Expand Up @@ -417,7 +419,7 @@ void GSRasterizer::writePixel(GS *gs, int x, int y, int z, uint8_t r, uint8_t g,

const AlphaTestResult alphaTest = classifyAlphaTest(ctx.test, a);

if (!alphaTest.writeFramebuffer)
if (!alphaTest.writeFramebuffer && !alphaTest.writeDepth)
return;

u8* vram = gs->m_vram;
Expand Down Expand Up @@ -544,9 +546,12 @@ void GSRasterizer::writePixel(GS *gs, int x, int y, int z, uint8_t r, uint8_t g,
pixel = Rgba8888ToRgba5551(pixel);
}

gs->WriteVram(fpsm, fbp, fbw, x, y, pixel);
if (alphaTest.writeFramebuffer)
{
gs->WriteVram(fpsm, fbp, fbw, x, y, pixel);
}

if (!zmask)
if (alphaTest.writeDepth && !zmask)
{
gs->WriteVram(zpsm, zbp, fbw, x, y, z);
}
Expand Down
184 changes: 184 additions & 0 deletions ps2xTest/src/ps2_gs_tests.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
#include "ps2_runtime.h"
#include "ps2_stubs.h"
#include "ps2_syscalls.h"
#include "runtime/ps2_gs_common.h"
#include "runtime/ps2_gs_gpu.h"
#include "runtime/ps2_gs_memory.h"
#include "runtime/ps2_gs_psmct32.h"
Expand Down Expand Up @@ -3068,6 +3069,189 @@ void register_ps2_gs_tests()
"AFAIL=RGB_ONLY should update RGB while preserving destination alpha");
});

tc.Run("GS alpha test AFAIL Z-buffer-only writes depth but not color", [](TestCase &t)
{
std::vector<uint8_t> vram(PS2_GS_VRAM_SIZE, 0u);
GS gs;
gs.init(vram.data(), static_cast<uint32_t>(vram.size()), nullptr);

constexpr uint32_t kFbw = 1u;
constexpr uint32_t kZbp = 1u; // ZBUF page, distinct from the color page
const uint32_t zBlock = GSInternal::framePageBaseToBlock(kZbp);

constexpr uint32_t kColorSentinel = 0xAB030201u;
constexpr uint32_t kZSentinel = 0x11111111u;
constexpr uint32_t kDrawnZ = 0x12345678u;

std::memcpy(vram.data(), &kColorSentinel, sizeof(kColorSentinel));
gs.WriteVram(GS_PSM_Z32, zBlock, kFbw, 0u, 0u, kZSentinel);

constexpr uint64_t kFrame =
(0ull << 0) |
(1ull << 16) |
(static_cast<uint64_t>(GS_PSM_CT32) << 24);
const uint64_t kZbuf = static_cast<uint64_t>(kZbp) << 0; // ZBP=1, PSM nibble=0 (Z32), ZMSK=0
constexpr uint64_t kScissor =
(0ull << 0) |
(0ull << 16) |
(0ull << 32) |
(0ull << 48);
constexpr uint64_t kTest =
1ull | // ATE
(5ull << 1) | // ATST = GEQUAL
(0x80ull << 4) | // AREF
(2ull << 12) | // AFAIL = ZB_ONLY
(1ull << 17); // ZTST = ALWAYS
constexpr uint64_t kPrim =
static_cast<uint64_t>(GS_PRIM_POINT);
constexpr uint64_t kRgbaq =
(0x12ull << 0) |
(0x34ull << 8) |
(0x56ull << 16) |
(0x00ull << 24) |
(0x3F800000ull << 32); // q = 1.0f
const uint64_t kXyz2 = static_cast<uint64_t>(kDrawnZ) << 32;

gs.writeRegister(GS_REG_FRAME_1, kFrame);
gs.writeRegister(GS_REG_ZBUF_1, kZbuf);
gs.writeRegister(GS_REG_SCISSOR_1, kScissor);
gs.writeRegister(GS_REG_TEST_1, kTest);
gs.writeRegister(GS_REG_PRIM, kPrim);
gs.writeRegister(GS_REG_RGBAQ, kRgbaq);
gs.writeRegister(GS_REG_XYZ2, kXyz2);

uint32_t pixel = 0u;
std::memcpy(&pixel, vram.data(), sizeof(pixel));
t.Equals(pixel, kColorSentinel,
"AFAIL=ZB_ONLY must not write the framebuffer when the alpha test fails");

const uint32_t depthResult = gs.ReadVram(GS_PSM_Z32, zBlock, kFbw, 0u, 0u);
t.Equals(depthResult, kDrawnZ,
"AFAIL=ZB_ONLY must still write depth when the alpha test fails");
});

tc.Run("GS alpha test AFAIL framebuffer-only leaves the depth buffer unwritten", [](TestCase &t)
{
std::vector<uint8_t> vram(PS2_GS_VRAM_SIZE, 0u);
GS gs;
gs.init(vram.data(), static_cast<uint32_t>(vram.size()), nullptr);

constexpr uint32_t kFbw = 1u;
constexpr uint32_t kZbp = 1u; // ZBUF page, distinct from the color page
const uint32_t zBlock = GSInternal::framePageBaseToBlock(kZbp);

constexpr uint32_t kColorSentinel = 0xAB030201u;
constexpr uint32_t kZSentinel = 0x11111111u;
constexpr uint32_t kDrawnZ = 0x12345678u;

std::memcpy(vram.data(), &kColorSentinel, sizeof(kColorSentinel));
gs.WriteVram(GS_PSM_Z32, zBlock, kFbw, 0u, 0u, kZSentinel);

constexpr uint64_t kFrame =
(0ull << 0) |
(1ull << 16) |
(static_cast<uint64_t>(GS_PSM_CT32) << 24);
const uint64_t kZbuf = static_cast<uint64_t>(kZbp) << 0; // ZBP=1, PSM nibble=0 (Z32), ZMSK=0
constexpr uint64_t kScissor =
(0ull << 0) |
(0ull << 16) |
(0ull << 32) |
(0ull << 48);
constexpr uint64_t kTest =
1ull | // ATE
(5ull << 1) | // ATST = GEQUAL
(0x80ull << 4) | // AREF
(1ull << 12) | // AFAIL = FB_ONLY
(1ull << 17); // ZTST = ALWAYS
constexpr uint64_t kPrim =
static_cast<uint64_t>(GS_PRIM_POINT);
constexpr uint64_t kRgbaq =
(0x12ull << 0) |
(0x34ull << 8) |
(0x56ull << 16) |
(0x00ull << 24) |
(0x3F800000ull << 32); // q = 1.0f
const uint64_t kXyz2 = static_cast<uint64_t>(kDrawnZ) << 32;

gs.writeRegister(GS_REG_FRAME_1, kFrame);
gs.writeRegister(GS_REG_ZBUF_1, kZbuf);
gs.writeRegister(GS_REG_SCISSOR_1, kScissor);
gs.writeRegister(GS_REG_TEST_1, kTest);
gs.writeRegister(GS_REG_PRIM, kPrim);
gs.writeRegister(GS_REG_RGBAQ, kRgbaq);
gs.writeRegister(GS_REG_XYZ2, kXyz2);

uint32_t pixel = 0u;
std::memcpy(&pixel, vram.data(), sizeof(pixel));
t.Equals(pixel, 0x00563412u,
"AFAIL=FB_ONLY must write the framebuffer when the alpha test fails");

const uint32_t depthResult = gs.ReadVram(GS_PSM_Z32, zBlock, kFbw, 0u, 0u);
t.Equals(depthResult, kZSentinel,
"AFAIL=FB_ONLY must NOT write depth when the alpha test fails");
});

tc.Run("GS alpha test AFAIL RGB-only leaves the depth buffer unwritten", [](TestCase &t)
{
std::vector<uint8_t> vram(PS2_GS_VRAM_SIZE, 0u);
GS gs;
gs.init(vram.data(), static_cast<uint32_t>(vram.size()), nullptr);

constexpr uint32_t kFbw = 1u;
constexpr uint32_t kZbp = 1u; // ZBUF page, distinct from the color page
const uint32_t zBlock = GSInternal::framePageBaseToBlock(kZbp);

constexpr uint32_t kColorSentinel = 0xAB030201u;
constexpr uint32_t kZSentinel = 0x11111111u;
constexpr uint32_t kDrawnZ = 0x12345678u;

std::memcpy(vram.data(), &kColorSentinel, sizeof(kColorSentinel));
gs.WriteVram(GS_PSM_Z32, zBlock, kFbw, 0u, 0u, kZSentinel);

constexpr uint64_t kFrame =
(0ull << 0) |
(1ull << 16) |
(static_cast<uint64_t>(GS_PSM_CT32) << 24);
const uint64_t kZbuf = static_cast<uint64_t>(kZbp) << 0; // ZBP=1, PSM nibble=0 (Z32), ZMSK=0
constexpr uint64_t kScissor =
(0ull << 0) |
(0ull << 16) |
(0ull << 32) |
(0ull << 48);
constexpr uint64_t kTest =
1ull | // ATE
(5ull << 1) | // ATST = GEQUAL
(0x80ull << 4) | // AREF
(3ull << 12) | // AFAIL = RGB_ONLY
(1ull << 17); // ZTST = ALWAYS
constexpr uint64_t kPrim =
static_cast<uint64_t>(GS_PRIM_POINT);
constexpr uint64_t kRgbaq =
(0x12ull << 0) |
(0x34ull << 8) |
(0x56ull << 16) |
(0x00ull << 24) |
(0x3F800000ull << 32); // q = 1.0f
const uint64_t kXyz2 = static_cast<uint64_t>(kDrawnZ) << 32;

gs.writeRegister(GS_REG_FRAME_1, kFrame);
gs.writeRegister(GS_REG_ZBUF_1, kZbuf);
gs.writeRegister(GS_REG_SCISSOR_1, kScissor);
gs.writeRegister(GS_REG_TEST_1, kTest);
gs.writeRegister(GS_REG_PRIM, kPrim);
gs.writeRegister(GS_REG_RGBAQ, kRgbaq);
gs.writeRegister(GS_REG_XYZ2, kXyz2);

uint32_t pixel = 0u;
std::memcpy(&pixel, vram.data(), sizeof(pixel));
t.Equals(pixel, 0xAB563412u,
"AFAIL=RGB_ONLY must write RGB and preserve destination alpha when the alpha test fails");

const uint32_t depthResult = gs.ReadVram(GS_PSM_Z32, zBlock, kFbw, 0u, 0u);
t.Equals(depthResult, kZSentinel,
"AFAIL=RGB_ONLY must NOT write depth when the alpha test fails");
});

tc.Run("GS triangle fan subpixel quad fills rows without interior holes", [](TestCase &t)
{
std::vector<uint8_t> vram(PS2_GS_VRAM_SIZE, 0u);
Expand Down