float4 mainImage(VertData v_in) : TARGET
{
    float4 color = image.Sample(textureSampler, v_in.uv);
    float t = elapsed_time * speed;
    float pi = 3.1415f;
    return float4(color.r*sin(x)/2f+0.5f, color.g*sin(x - pi/2f)/2f+0.5f, color.b*sin(x - pi)/2f+0.5f);
}