X-Git-Url: https://git.sesse.net/?p=movit;a=blobdiff_plain;f=overlay_effect.frag;h=d32cc062204c4492dbb552c6930908e2f8b805be;hp=36c1a7996cf48e0112908d93aa1b9634698ed2fa;hb=009c7510df1ac1b70662b0085ebaf1a619dd761a;hpb=b10c546f579c7ccb5939161e61a71cd18a3f9bbd

diff --git a/overlay_effect.frag b/overlay_effect.frag
index 36c1a79..d32cc06 100644
--- a/overlay_effect.frag
+++ b/overlay_effect.frag
@@ -13,24 +13,15 @@
 // C_o without the division by alpha_o).
 
 vec4 FUNCNAME(vec2 tc) {
+// SWAP_INPUTS will be #defined to 1 if we want to swap the two inputs,
+#if SWAP_INPUTS
+	vec4 bottom = INPUT2(tc);
+	vec4 top = INPUT1(tc);
+#else
 	vec4 bottom = INPUT1(tc);
 	vec4 top = INPUT2(tc);
-#if 0
-	// Postmultiplied version.
-	float new_alpha = mix(bottom.a, 1.0, top.a);
-	if (new_alpha < 1e-6) {
-		// new_alpha = 0 only if top.a = bottom.a = 0, at least as long as
-		// both alphas are within range. (If they're not, the result is not
-		// meaningful anyway.) And if new_alpha = 0, we don't really have
-		// any meaningful output anyway, so just set it to zero instead of
-		// getting division-by-zero below.
-		return vec4(0.0);
-	} else {
-		vec3 premultiplied_color = mix(bottom.rgb * bottom.aaa, top.rgb, top.a);
-		vec3 color = premultiplied_color / new_alpha;
-		return vec4(color.r, color.g, color.b, new_alpha);
-	}
-#else
-	return top + (1.0 - top.a) * bottom;
 #endif
+	return top + (1.0 - top.a) * bottom;
 }
+
+#undef SWAP_INPUTS