out vec2 fragPos;
out vec2 fragUV;

uniform vec2 pos;
uniform vec2 size;
uniform float rotation;

void main(){
//gl_Position is OpenGL defined
gl_Position.z = 0.0;
gl_Position.w = 1.0;
gl_Position.x = vertPos.x + pos.x*2 - 1;
gl_Position.y = vertPos.y + pos.y*2 - 1;

mat4 rotationMat = mat4(cos(rotation), sin(rotation) * -1, 0, 0,
                        sin(rotation), cos(rotation), 0, 0,
                        0, 0, 1, 0,
                        0, 0, 0, 1);


gl_Position *= rotateZ;

//vec2 size
if(size.x != 0 || size.y != 0){
    if(gl_VertexID != 0){
        switch(gl_VertexID){
            case 1: gl_Position.x += size.x; break;
            case 2: gl_Position.y += size.y; break;
            case 3: gl_Position.y += size.y; break;
            case 4: gl_Position.x += size.x; gl_Position.y += size.y; break;
            case 5: gl_Position.x += size.x; break;
        }
    }
}


fragPos = vertPos;
fragUV = vec2(vertUV.x, 1.0 - vertUV.y);
}