Rewrite decode32 again with a hybrid approach

fuzzie360 · fuzzie360 · commit 16d6d4762b2e · 2016-03-02T13:05:28.000+08:00
diff --git a/src/backend/mode_gpu.js b/src/backend/mode_gpu.js
@@ -320,13 +320,12 @@
 					'	int b = int(rgba.b);',
 					'	int a = int(rgba.a);',
 					'	int sign = a > 127 ? -1 : 1;',
-					'	int exponent = 2 * (a > 127 ? a - 128 : a) + (b > 127 ? 1 : 0);',
-					'	if (exponent == 0) return float(sign) * 0.0;',
-					'	exponent -= 127;',
-					'	float f = exp2(float(exponent));',
-					'	f += float(b > 127 ? b - 128 : b) * exp2(float(exponent-7));',
-					'	f += float(g) * exp2(float(exponent-15));',
-					'	f += float(r) * exp2(float(exponent-23));',
+					'	float exponent = 2.0 * actuallyMod(rgba.a,128.0) + step(128.0,rgba.b) - 127.0;',
+					'	if (abs(exponent + 127.0) < 0.001) return 0.0;',
+					'	float f = exp2(exponent);',
+					'	f += float(b > 127 ? b - 128 : b) * exp2(exponent-float(7));',
+					'	f += float(g) * exp2(exponent-float(15));',
+					'	f += float(r) * exp2(exponent-float(23));',
 					'	f *= float(sign);',
 					'	return f;',
 					'}',
