Rewrite decode32 again

fuzzie360 · fuzzie360 · commit 951824c951a7 · 2016-03-02T11:03:45.000+08:00
diff --git a/src/backend/mode_gpu.js b/src/backend/mode_gpu.js
@@ -315,11 +315,20 @@
 					'highp float decode32(highp vec4 rgba) {',
 					(endianness == 'LE' ? '' : '	rgba.rgba = rgba.abgr;'),
 					'	rgba *= 255.0;',
-					'	float sign = 1.0 - step(128.0,rgba.a)*2.0;',
-					'	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 mantissa = actuallyMod(rgba.b,128.0)*65536.0 + rgba.g*256.0 +rgba.r+ float(0x800000);',
-					'	return sign * exp2(exponent-23.0) * mantissa;',
+					'	int r = int(rgba.r);',
+					'	int g = int(rgba.g);',
+					'	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));',
+					'	f *= float(sign);',
+					'	return f;',
 					'}',
 					'/* End: http://stackoverflow.com/questions/7059962/how-do-i-convert-a-vec4-rgba-value-to-a-float */',
 					'#else',
@@ -368,6 +377,7 @@
 					'	float index = (xyz.z * texDim.x * texDim.y) + (xyz.y * texDim.x) + xyz.x;',
 					'	float t = floor(index / texSize.x);',
 					'	float s = actuallyMod(index, texSize.x);',
+					'	if (s > texSize.x - 0.00001) s = 0.0;',
 					'	s += 0.5;',
 					'	t += 0.5;',
 					(opt.safeTextureReadHack ? 's += 1.0; t += 1.0;' : ''),
