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Do perspective correction with floating-point math

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Fixes Actua Soccer with Matrox Mystique patch
This commit is contained in:
Cacodemon345
2025-12-20 21:58:12 +06:00
parent e3a2bca761
commit 3b8dc9a0c1
1 changed files with 42 additions and 10 deletions
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52
src/video/vid_mga.c
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@@ -18,6 +18,7 @@
#include <string.h>
#include <stdlib.h>
#include <wchar.h>
#include <math.h>
#include <stdatomic.h>
#include <86box/86box.h>
#include <86box/io.h>
@@ -5149,7 +5150,7 @@ static uint16_t texture_texel_fetch(mystique_t *mystique, int *tex_r, int *tex_g
*atransp = 0;
break;
case TEXCTL_TEXFORMAT_TW15:
src = ((uint16_t *) svga->vram)[((mystique->dwgreg.texorg >> 1) + (t * tex_pitch) + s) & mystique->vram_mask_w];
src = *(uint16_t*)((&svga->vram[(mystique->dwgreg.texorg + ((t * tex_pitch) + s) * 2) & mystique->vram_mask]));
*tex_r = ((src >> 10) & 0x1f) << 3;
*tex_g = ((src >> 5) & 0x1f) << 3;
*tex_b = (src & 0x1f) << 3;
@@ -5159,7 +5160,7 @@ static uint16_t texture_texel_fetch(mystique_t *mystique, int *tex_r, int *tex_g
*atransp = 0;
break;
case TEXCTL_TEXFORMAT_TW12:
src = ((uint16_t *) svga->vram)[((mystique->dwgreg.texorg >> 1) + (t * tex_pitch) + s) & mystique->vram_mask_w];
src = *(uint16_t*)((&svga->vram[(mystique->dwgreg.texorg + ((t * tex_pitch) + s) * 2) & mystique->vram_mask]));
*tex_r = ((src >> 8) & 0xf) << 4;
*tex_g = ((src >> 4) & 0xf) << 4;
*tex_b = (src & 0xf) << 4;
@@ -5173,7 +5174,7 @@ static uint16_t texture_texel_fetch(mystique_t *mystique, int *tex_r, int *tex_g
}
break;
case TEXCTL_TEXFORMAT_TW16:
src = ((uint16_t *) svga->vram)[((mystique->dwgreg.texorg >> 1) + (t * tex_pitch) + s) & mystique->vram_mask_w];
src = *(uint16_t*)((&svga->vram[(mystique->dwgreg.texorg + ((t * tex_pitch) + s) * 2) & mystique->vram_mask]));
*tex_r = (src >> 11) << 3;
*tex_g = ((src >> 5) & 0x3f) << 2;
*tex_b = (src & 0x1f) << 3;
@@ -5190,6 +5191,40 @@ static double lerp(double v0, double v1, double t) {
return (1. - t) * v0 + t * v1;
}
// Taken from GZDoom.
static inline double
FixedToFloat(int fixed)
{
return fixed * (1.0 / (1 << 16));
}
static inline void
persp_correct(mystique_t* mystique, int* s, int* t, int* q, double* s_frac, double* t_frac)
{
const int s_shift = 20 - (mystique->dwgreg.texwidth & TEXWIDTH_TW_MASK);
const int t_shift = 20 - (mystique->dwgreg.texheight & TEXHEIGHT_TH_MASK);
double s_d = ((*s) >> s_shift);
double t_d = ((*t) >> t_shift);
double q_d = FixedToFloat(*q);
double throwaway1 = 0;
double throwaway2 = 0;
if (q_d == 0.0)
q_d = INFINITY;
s_d *= 1. / q_d;
t_d *= 1. / q_d;
*s_frac = fabs(modf(s_d, &throwaway1));
*t_frac = fabs(modf(s_d, &throwaway2));
(void)throwaway1;
(void)throwaway2;
*s = s_d;
*t = t_d;
}
static int
texture_read(mystique_t *mystique, int *tex_r, int *tex_g, int *tex_b, int *atransp, int *tex_a)
{
@@ -5223,14 +5258,11 @@ texture_read(mystique_t *mystique, int *tex_r, int *tex_g, int *tex_b, int *atra
s_frac = (((int32_t) mystique->dwgreg.tmr[6]) & ((1 << s_shift) - 1)) / (double)(1 << s_shift);
t_frac = (((int32_t) mystique->dwgreg.tmr[7]) & ((1 << t_shift) - 1)) / (double)(1 << t_shift);
} else {
const int s_shift = (20 + 16) - (mystique->dwgreg.texwidth & TEXWIDTH_TW_MASK);
const int t_shift = (20 + 16) - (mystique->dwgreg.texheight & TEXHEIGHT_TH_MASK);
int64_t q = mystique->dwgreg.tmr[8] ? (0x100000000LL / (int64_t) (int32_t) mystique->dwgreg.tmr[8]) : 0;
int q = (int32_t)mystique->dwgreg.tmr[8];
s = (int32_t) mystique->dwgreg.tmr[6];
t = (int32_t) mystique->dwgreg.tmr[7];
s = ((int64_t) (int32_t) mystique->dwgreg.tmr[6] * q) >> s_shift;
t = ((int64_t) (int32_t) mystique->dwgreg.tmr[7] * q) >> t_shift;
s_frac = (((int64_t) (int32_t) mystique->dwgreg.tmr[6] * q) & ((1 << s_shift) - 1)) / (double)(1 << s_shift);
t_frac = (((int64_t) (int32_t) mystique->dwgreg.tmr[7] * q) & ((1 << t_shift) - 1)) / (double)(1 << t_shift);
persp_correct(mystique, &s, &t, &q, &s_frac, &t_frac);
}
if (mystique->dwgreg.texctl & TEXCTL_CLAMPU) {