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softgpu: Round tex coords properly for nearest #8282

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Dec 21, 2015
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softgpu: Round tex coords properly for nearest #8282

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22 changes: 11 additions & 11 deletions GPU/Software/Rasterizer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -114,11 +114,11 @@ static inline u8 ClampFogDepth(float fogdepth) {

static inline void GetTexelCoordinates(int level, float s, float t, int& out_u, int& out_v)
{
int width = 1 << (gstate.texsize[level] & 0xf);
int height = 1 << ((gstate.texsize[level]>>8) & 0xf);
int width = gstate.getTextureWidth(level);
int height = gstate.getTextureHeight(level);

int u = (int)(s * width);
int v = (int)(t * height);
int u = (int)(s * width + 0.375f);
int v = (int)(t * height + 0.375f);
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Turns out this is wrong. In fact, I think we are half a pixel off for bilinear (i.e. a 0,0 -> 1,1 box will apply 50% of texel 1,1 in the center, which is of course wrong.)

-[Unknown]

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That's interesting - I hadn't considered the possibility that the offset might need to be different in each of the filtering modes - who knows how they are implemented.

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@unknownbrackets unknownbrackets May 7, 2017 •
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Well, AFAICT it's just 0 for nearest (seems to round right at 0.5) and -0.5 for linear (to sample at the centers.) Need to check some throughmode handling still when I have time.

I did try applying a 0.375f / 256.0f offset to correct for rounding issues, which seemed to largely help most everywhere (including Crisis Core.) And with that the Hexyz issue doesn't happen either (probably the same rounding issue.) However, it introduces other issues...

Also tex wrap with negative float uvs was wrong.

-[Unknown]


if (gstate.isTexCoordClampedS()) {
if (u >= width - 1)
Expand All @@ -144,8 +144,8 @@ static inline void GetTexelCoordinates(int level, float s, float t, int& out_u,
static inline void GetTexelCoordinatesQuad(int level, float in_s, float in_t, int u[4], int v[4], int &frac_u, int &frac_v)
{
// 8 bits of fractional UV
int width = 1 << (gstate.texsize[level] & 0xf);
int height = 1 << ((gstate.texsize[level]>>8) & 0xf);
int width = gstate.getTextureWidth(level);
int height = gstate.getTextureHeight(level);

int base_u = in_s * width * 256;
int base_v = in_t * height * 256;
Expand Down Expand Up @@ -190,9 +190,9 @@ static inline void GetTexelCoordinatesQuad(int level, float in_s, float in_t, in

static inline void GetTexelCoordinatesThrough(int level, int s, int t, int& u, int& v)
{
// Not actually sure which clamp/wrap modes should be applied. Let's just wrap for now.
int width = 1 << (gstate.texsize[level] & 0xf);
int height = 1 << ((gstate.texsize[level]>>8) & 0xf);
// TODO: Not actually sure which clamp/wrap modes should be applied. Let's just wrap for now.
int width = gstate.getTextureWidth(level);
int height = gstate.getTextureHeight(level);

// Wrap!
u = ((unsigned int)(s) & (width - 1));
Expand All @@ -202,8 +202,8 @@ static inline void GetTexelCoordinatesThrough(int level, int s, int t, int& u, i
static inline void GetTexelCoordinatesThroughQuad(int level, int s, int t, int *u, int *v)
{
// Not actually sure which clamp/wrap modes should be applied. Let's just wrap for now.
int width = 1 << (gstate.texsize[level] & 0xf);
int height = 1 << ((gstate.texsize[level] >> 8) & 0xf);
int width = gstate.getTextureWidth(level);
int height = gstate.getTextureHeight(level);

// Wrap!
for (int i = 0; i < 4; i++) {
Expand Down