voxel-test/resources/shaders/tiling.fs

#version 330 core

uniform sampler2D diffuseMap;
uniform vec2 textureTiling;

in vec2 fragTexCoord;
in vec3 fragNormal;
in vec2 fragTileTexCoord;

flat in uvec4 occlusionSides;
flat in int topLeftObscured;
flat in int topRightObscured;
flat in int bottomLeftObscured;
flat in int bottomRightObscured;
flat in int quadHeight;
flat in int quadWidth;

out vec4 outColor;

// this is a shitty approximation of arcsin(x)/pi that gets the tails right and is reasonably close to the actual arcsin(x)/pi curve.
float fakeArcsin(float x) {
    x = clamp(x, -1.0, 1.0);
    float ax = abs(x);
    float sqrtPart = sqrt(1.0 - ax);
    float result = 0.5 - sqrtPart * (0.5 - 0.06667 * ax);
    return x < 0.0 ? -result : result;
}

void main()
{
    vec2 texCoord = (floor(fragTexCoord*textureTiling) + fract(fragTileTexCoord)) / textureTiling;
    outColor = texture(diffuseMap, texCoord);

    ivec2 floorFragTileTexCoord = ivec2(fragTileTexCoord);

    if(floorFragTileTexCoord.x < 1 && ((occlusionSides.x >> floorFragTileTexCoord.x) & uint(1)) == uint(1)) {
        outColor *= 0.5 + fakeArcsin(fragTileTexCoord.x);
    }

    outColor.a = 1;

    uint bit = uint(fragTileTexCoord * 32);
    outColor.g = (((occlusionSides.x >> bit) & uint(1)) == uint(1)) ? 
                  ((bit % uint(2) == uint(0)) ? 1.0 : 0.8): 
                  ((bit % uint(2) == uint(0)) ? 0.0 : 0.2);
}