ps.1.1
// Alpha blend color, output sum of alphas
// Color is t0 * (1 - t1.a) + t1 * t1.a
// Alpha is t0.a + t1.a
tex t0
tex t1
lrp r0.rgb, t1.a, t1, t0
add r0.a, t0, t1;
mul r0, r0, v0;