Fake 3D shader

const vec2 center=vec2(0.5,0.5);
vec4 fake3Dpixel(sampler2D tex,vec2 pos,vec4 coord,int samp){
    vec4 cur;
    vec4 col;
    for (int i=samp;i>0;i--){
        cur=texture(tex,
            -((pos-center)*(-1+((i-(samp+coord.b))*(coord.a/scale))))+(center+coord.rg)
        );
        col=col.a<cur.a ? cur : col;
    }
    return col;
}