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libobs: Improve low-resolution bilinear sampling 

The issue with the current bilinear_lowres_scale effect is that it
samples adjacent texels, disregarding the texel-to-pixel ratio. If the
ratio is large, this can lead to aliasing. This change provides a fair
set of texture samples across the entire pixel.

The 8-sample pattern used here comes from Direct3D.
master
James Park 2019-05-13 23:54:14 -07:00
parent 42c190f3d6
commit fede4fb784
1 changed files with 18 additions and 14 deletions
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32
libobs/data/bilinear_lowres_scale.effect
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@ -1,12 +1,11 @@
/*
* bilinear low res scaling, samples 9 pixels of a larger image to scale to a
* bilinear low res scaling, samples 8 pixels of a larger image to scale to a
* low resolution image below half size
*/
uniform float4x4 ViewProj;
uniform texture2d image;
uniform float4x4 color_matrix;
uniform float2 base_dimension_i;
sampler_state textureSampler {
Filter = Linear;
@ -34,19 +33,24 @@ float4 pixel(float2 uv)
float4 DrawLowresBilinear(VertData v_in)
{
float2 stepxy = base_dimension_i;
float4 out_color;
float2 uv = v_in.uv;
float2 stepxy = float2(ddx(uv.x), ddy(uv.y));
float2 stepxy1 = stepxy * 0.0625;
float2 stepxy3 = stepxy * 0.1875;
float2 stepxy5 = stepxy * 0.3125;
float2 stepxy7 = stepxy * 0.4375;
out_color = pixel(v_in.uv);
out_color += pixel(v_in.uv + float2(-stepxy.x, -stepxy.y));
out_color += pixel(v_in.uv + float2(-stepxy.x, 0.0));
out_color += pixel(v_in.uv + float2(-stepxy.x, stepxy.y));
out_color += pixel(v_in.uv + float2( 0.0, -stepxy.y));
out_color += pixel(v_in.uv + float2( 0.0, stepxy.y));
out_color += pixel(v_in.uv + float2( stepxy.x, -stepxy.y));
out_color += pixel(v_in.uv + float2( stepxy.x, 0.0));
out_color += pixel(v_in.uv + float2( stepxy.x, stepxy.y));
return out_color / float4(9.0, 9.0, 9.0, 9.0);
// Simulate Direct3D 8-sample pattern
float4 out_color;
out_color = pixel(uv + float2( stepxy1.x, -stepxy3.y));
out_color += pixel(uv + float2(-stepxy1.x, stepxy3.y));
out_color += pixel(uv + float2( stepxy5.x, stepxy1.y));
out_color += pixel(uv + float2(-stepxy3.x, -stepxy5.y));
out_color += pixel(uv + float2(-stepxy5.x, stepxy5.y));
out_color += pixel(uv + float2(-stepxy7.x, -stepxy1.y));
out_color += pixel(uv + float2( stepxy3.x, stepxy7.y));
out_color += pixel(uv + float2( stepxy7.x, -stepxy7.y));
return out_color * 0.125;
}
float4 PSDrawLowresBilinearRGBA(VertData v_in) : TARGET