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uniform sampler2D colorBuffer;
uniform sampler2D depthBuffer;
uniform int bgType;
uniform vec4 colorOverride;
in vec4 uvcoordsvar;
out vec4 fragColor;
#define BG_SOLID 0
#define BG_GRADIENT 1
#define BG_CHECKER 2
#define BG_RADIAL 3
#define SQRT2 1.4142135623730950488
/* 4x4 bayer matrix prepared for 8bit UNORM precision error. */
#define P(x) (((x + 0.5) * (1.0 / 16.0) - 0.5) * (1.0 / 255.0))
const vec4 dither_mat4x4[4] = vec4[4](vec4(P(0.0), P(8.0), P(2.0), P(10.0)),
vec4(P(12.0), P(4.0), P(14.0), P(6.0)),
vec4(P(3.0), P(11.0), P(1.0), P(9.0)),
vec4(P(15.0), P(7.0), P(13.0), P(5.0)));
float dither(void)
{
ivec2 co = ivec2(gl_FragCoord.xy) % 4;
return dither_mat4x4[co.x][co.y];
}
void main()
{
/* The blend equation is:
* resutl.rgb = SRC.rgb * (1 - DST.a) + DST.rgb * (SRC.a)
* result.a = SRC.a * 0 + DST.a * SRC.a
* This removes the alpha channel and put the background behind reference images
* while masking the reference images by the render alpha.
*/
float alpha = texture(colorBuffer, uvcoordsvar.st).a;
float depth = texture(depthBuffer, uvcoordsvar.st).r;
vec3 bg_col;
vec3 col_high;
vec3 col_low;
switch (bgType) {
case BG_SOLID:
bg_col = colorBackground.rgb;
break;
case BG_GRADIENT:
/* XXX do interpolation in a non-linear space to have a better visual result. */
col_high = pow(colorBackground.rgb, vec3(1.0 / 2.2));
col_low = pow(colorBackgroundGradient.rgb, vec3(1.0 / 2.2));
bg_col = mix(col_low, col_high, uvcoordsvar.t);
/* Convert back to linear. */
bg_col = pow(bg_col, vec3(2.2));
/* Dither to hide low precision buffer. (Could be improved) */
bg_col += dither();
break;
case BG_RADIAL:
/* Do interpolation in a non-linear space to have a better visual result. */
col_high = pow(colorBackground.rgb, vec3(1.0 / 2.2));
col_low = pow(colorBackgroundGradient.rgb, vec3(1.0 / 2.2));
vec2 uv_n = uvcoordsvar.xy - 0.5;
bg_col = mix(col_high, col_low, length(uv_n) * SQRT2);
/* Convert back to linear. */
bg_col = pow(bg_col, vec3(2.2));
/* Dither to hide low precision buffer. (Could be improved) */
bg_col += dither();
break;
case BG_CHECKER:
float size = sizeChecker * sizePixel;
ivec2 p = ivec2(floor(gl_FragCoord.xy / size));
bool check = mod(p.x, 2) == mod(p.y, 2);
bg_col = (check) ? colorCheckerPrimary.rgb : colorCheckerSecondary.rgb;
break;
}
bg_col = mix(bg_col, colorOverride.rgb, colorOverride.a);
/* Mimic alpha under behavior. Result is premultiplied. */
fragColor = vec4(bg_col, 1.0) * (1.0 - alpha);
/* Special case: If the render is not transparent, do not clear alpha values. */
if (depth == 1.0 && alpha == 1.0) {
fragColor.a = 1.0;
}
}
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