Hifi fragment shader that rotates a white square on a black background.

rotatecube.fs

// Reelased into the Public Domain by Michael Bailey.

// Reminder that all GLSL code is run from top to bottom. This is why the main
// function getProceduralFragmentWith Position must always be on the bottom. 
// Other functions above that must be created before they can be used.

// This function creates draws a simple rectangle.
// position: 0.0 to 1.0 value for the rectangle's center position.
// scale: x and y values with a 0.0 to 0.1
float rectshape(vec2 position, vec2 scale){
    scale = vec2(0.5) - scale * 0.5;
    vec2 shaper = vec2(step(scale.x, position.x), step(scale.y, position.y));
    shaper *= vec2(step(scale.x, 1.0 - position.x), step(scale.y, 1.0 - position.y));
    return shaper.x * shaper.y;
}

// This function rotates the entire fragment by the supplied angle value.
mat2 rotate(float angle){
    return mat2(cos(angle), -sin(angle), sin(angle), cos(angle));
}

// This is the main entry point for a fragment shader on High Fidelity
float getProceduralFragmentWithPosition(inout ProceduralFragmentWithPosition proceduralData) {
    // Setup the initial coordinate and color values.
    vec2 coord = _texCoord0.st;
    vec3 color = vec3(0.0);

    // Why is the coordinate system being offset twice? Matrix math.
    coord -= vec2(0.5);
    // Rotate the entire fragment using a global time variable.
    coord = rotate(iGlobalTime) * coord;
    coord += vec2(0.5);

    // Draw a square using the rectshape function.
    color += vec3(rectshape(coord, vec2(0.3, 0.3)));

    // Send out color data to High Fidelity's data structure.
    proceduralData.diffuse = color;

    // This is required. Return the emmissive amount, which defaults to 0.0.
    return 0.0;
}