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VARYING vec2 center_vec;
void MAIN()
{
float dist_to_center = length(center_vec) / radius;
vec2 texc;
if (dist_to_center > 1.0) {
texc = INPUT_UV;
} else {
vec2 center_adj = vec2(center.x, 0.5 + (center.y - 0.5) * (-FRAMEBUFFER_Y_UP));
float rotation_amount = (1.0 - dist_to_center) * (1.0 - dist_to_center);
float r = radians(360.0) * rotation_amount * distortionStrength / 4.0 * FRAMEBUFFER_Y_UP;
float cos_r = cos(r);
float sin_r = sin(r);
mat2 rotation = mat2(cos_r, sin_r, -sin_r, cos_r);
texc = center_adj + rotation * (INPUT_UV - center_adj);
}
if (texc.x < 0.0 || texc.x > 1.0 || texc.y < 0.0 || texc.y > 1.0)
FRAGCOLOR = vec4(0.0);
else
FRAGCOLOR = texture(INPUT, texc);
}