affine.glsl

#version 150

// Using Kodelife for the realtime preview/test environment but it should work fine on any shader that
// - offers the output's resolution
// - a time clock in seconds
// - an UV mapped on screenspace from [0,0] to [1,1]    

uniform float time;
uniform vec2 resolution;

uniform sampler2D texture0;

in VertexData
{
    vec4 v_position;
    vec3 v_normal;
    vec2 v_texcoord;
} inData;

out vec4 fragColor;

void main(void)
{
    float ratio = resolution.x / resolution.y;
    vec2 squaredUV = inData.v_texcoord / vec2(ratio, 1);
    float z = (gl_FragCoord.y / resolution.y);
    if(z > 0.5)
    {
        fragColor.rgb = vec3(0.1,0.2,0.4)/2;
        return;
    }
    z *= 2;
    z = pow(z, 2);
    z = 1-cos(z*3.141592653/2);
    
    float xScale = 1;
    float yScale = 1;
    float xCenter = 0.6;
    float yCenter = 0;
    vec2 postOffset = vec2(0, z+time);
    float angle = 0;

    mat3 minusTranslation = mat3(1,0,-xCenter,
                                 0,1,-yCenter,
                                 0,0,1);
    mat3 translation = mat3(1,0,xCenter,
                            0,1,yCenter,
                            0,0,1);
    mat3 scale = mat3(xScale, 0, 0,
                      0, yScale, 0,
                      0, 0, 1);
    mat3 rotation = mat3(cos(angle), sin(angle), 0,
                         -sin(angle), cos(angle), 0,
                         0, 0, 1);

    mat3 transform = mat3(1,0,0,
                          0,1,0,
                          0,0,1);


    mat3 postTranslation = mat3(1,0,postOffset.x,
                            0,1,postOffset.y,
                            0,0,1);
    
    
    transform *= minusTranslation;
    transform *= rotation;
    transform *= scale;
    transform *= translation;
    transform *= postTranslation;
    vec3 mapped = vec3(squaredUV, 1) * transform;
    
    vec2 uv = vec2(mapped);
    
    vec4 mapFragment = texture(texture0, uv)  + pow(z,4) * 0.6;
    fragColor = mapFragment;
}