slang-shaders/retro/shaders/sharp-bilinear.slang

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#version 450
layout(std140, set = 0, binding = 0) uniform UBO
{
mat4 MVP;
vec4 OutputSize;
vec4 OriginalSize;
vec4 SourceSize;
} global;
/*
* sharp-bilinear.cg
* Author: Themaister
* License: Public domain
*
* Does a bilinear stretch, with a preapplied Nx nearest-neighbor scale, giving a
* sharper image than plain bilinear.
*/
#define SHARP_BILINEAR_PRE_SCALE 4.0
#pragma stage vertex
layout(location = 0) in vec4 Position;
layout(location = 1) in vec2 TexCoord;
layout(location = 0) out vec2 vTexCoord;
void main()
{
gl_Position = global.MVP * Position;
vTexCoord = TexCoord;
}
#pragma stage fragment
layout(location = 0) in vec2 vTexCoord;
layout(location = 0) out vec4 FragColor;
layout(set = 0, binding = 2) uniform sampler2D Source;
void main()
{
vec2 texel = vTexCoord * global.SourceSize.xy;
vec2 texel_floored = floor(texel);
vec2 s = fract(texel);
float region_range = 0.5 - 0.5 / SHARP_BILINEAR_PRE_SCALE;
// Figure out where in the texel to sample to get correct pre-scaled bilinear.
// Uses the hardware bilinear interpolator to avoid having to sample 4 times manually.
vec2 center_dist = s - 0.5;
vec2 f = (center_dist - clamp(center_dist, -region_range, region_range)) * SHARP_BILINEAR_PRE_SCALE + 0.5;
vec2 mod_texel = texel_floored + f;
FragColor = vec4(texture(Source, mod_texel / global.SourceSize.xy).rgb, 1.0);
}