30 lines
1.2 KiB
Plaintext
30 lines
1.2 KiB
Plaintext
// Object position in screen space. Allows the noise to
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// have a constant screen-space size, without being
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// affected by the widget layout/position.
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uniform highp vec2 objCoord;
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void fragment() {
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// Stamps have orientation, and the texture sampling is nearest
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// pixel, so run a bilinear filter to smooth out the edges.
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{
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highp vec4 tl = texture2D(TEXTURE, UV);
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highp vec4 tr = texture2D(TEXTURE, UV + vec2(TEXTURE_PIXEL_SIZE.x, 0.0));
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highp vec4 bl = texture2D(TEXTURE, UV + vec2(0.0, TEXTURE_PIXEL_SIZE.y));
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highp vec4 br = texture2D(TEXTURE, UV + TEXTURE_PIXEL_SIZE);
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highp vec2 textureSize = 1.0 / TEXTURE_PIXEL_SIZE;
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highp vec2 f = fract( UV * textureSize );
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highp vec4 tA = mix( tl, tr, f.x );
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highp vec4 tB = mix( bl, br, f.x );
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COLOR = mix( tA, tB, f.y );
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}
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// Add a bit of noise to mimic imperfect contact with the paper
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{
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highp float stampNoise = zNoise((FRAGCOORD.xy - objCoord) * vec2(0.03, 0.03)) *
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zNoise((FRAGCOORD.xy - objCoord) * vec2(0.08, 0.08));
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COLOR.a *= min(0.9, 0.4 + smoothstep(0.05, 0.3, stampNoise));
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}
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}
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