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91 lines
2.0 KiB
C++
91 lines
2.0 KiB
C++
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#include "SingleColorLookup.h"
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#include "nvcore/Debug.h"
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#include <stdlib.h> // abs
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// Globals
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uint8 OMatch5[256][2];
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uint8 OMatch6[256][2];
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uint8 OMatchAlpha5[256][2];
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uint8 OMatchAlpha6[256][2];
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static int Mul8Bit(int a, int b)
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{
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int t = a * b + 128;
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return (t + (t >> 8)) >> 8;
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}
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static inline int Lerp13(int a, int b)
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{
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#ifdef DXT_USE_ROUNDING_BIAS
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// with rounding bias
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return a + Mul8Bit(b-a, 0x55);
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#else
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// without rounding bias
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// replace "/ 3" by "* 0xaaab) >> 17" if your compiler sucks or you really need every ounce of speed.
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return (a * 2 + b) / 3;
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#endif
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}
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static void PrepareOptTable(uint8 * table, const uint8 * expand, int size, bool alpha_mode)
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{
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for (int i = 0; i < 256; i++)
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{
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int bestErr = 256 * 100;
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for (int min = 0; min < size; min++)
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{
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for (int max = 0; max < size; max++)
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{
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int mine = expand[min];
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int maxe = expand[max];
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int err;
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if (alpha_mode) err = abs((maxe + mine)/2 - i);
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else err = abs(Lerp13(maxe, mine) - i);
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err *= 100;
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// DX10 spec says that interpolation must be within 3% of "correct" result,
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// add this as error term. (normally we'd expect a random distribution of
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// +-1.5% error, but nowhere in the spec does it say that the error has to be
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// unbiased - better safe than sorry).
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err += abs(max - min) * 3;
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if (err < bestErr)
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{
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table[i*2+0] = max;
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table[i*2+1] = min;
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bestErr = err;
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}
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}
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}
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}
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}
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NV_AT_STARTUP(initSingleColorLookup());
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void initSingleColorLookup()
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{
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uint8 expand5[32];
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uint8 expand6[64];
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for (int i = 0; i < 32; i++) {
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expand5[i] = (i<<3) | (i>>2);
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}
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for (int i = 0; i < 64; i++) {
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expand6[i] = (i<<2) | (i>>4);
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}
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PrepareOptTable(&OMatch5[0][0], expand5, 32, false);
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PrepareOptTable(&OMatch6[0][0], expand6, 64, false);
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PrepareOptTable(&OMatchAlpha5[0][0], expand5, 32, true);
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PrepareOptTable(&OMatchAlpha6[0][0], expand6, 64, true);
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}
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