From d84beeeff32fe401accd51f16ff9f669f516538a Mon Sep 17 00:00:00 2001 From: Alan Hickman Date: Sat, 24 Apr 2021 13:08:03 -0700 Subject: [PATCH] stb_dxt: Initialize tables at compile time Also fix a "potentially uninitialized variable" warning. This is a modified version of Alan's original PR that keeps the table generator in the file (in case there's interest) and also replaces the expand[] tables with math, since it's trivial. Fixes issue #1117. --- stb_dxt.h | 267 ++++++++++++++++++++++++++++++++++++++---------------- 1 file changed, 191 insertions(+), 76 deletions(-) diff --git a/stb_dxt.h b/stb_dxt.h index 04666de..b37e543 100644 --- a/stb_dxt.h +++ b/stb_dxt.h @@ -29,6 +29,7 @@ // Kevin Schmidt (#defines for "freestanding" compilation) // github:ppiastucki (BC4 support) // Ignacio Castano - improve DXT endpoint quantization +// Alan Hickman - static table initialization // // LICENSE // @@ -81,14 +82,10 @@ STBDDEF void stb_compress_bc5_block(unsigned char *dest, const unsigned char *sr #include -#if !defined(STBD_ABS) || !defined(STBI_FABS) +#if !defined(STBI_FABS) #include #endif -#ifndef STBD_ABS -#define STBD_ABS(i) abs(i) -#endif - #ifndef STBD_FABS #define STBD_FABS(x) fabs(x) #endif @@ -98,12 +95,112 @@ STBDDEF void stb_compress_bc5_block(unsigned char *dest, const unsigned char *sr #define STBD_MEMSET memset #endif -static unsigned char stb__Expand5[32]; -static unsigned char stb__Expand6[64]; -static unsigned char stb__OMatch5[256][2]; -static unsigned char stb__OMatch6[256][2]; -static unsigned char stb__QuantRBTab[256+16]; -static unsigned char stb__QuantGTab[256+16]; +static const unsigned char stb__QuantRBTab[256 + 16] = { + 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 8, 8, 8, + 8, 8, 8, 8, 8, 16, 16, 16, 16, 16, 16, 16, 16, 24, 24, 24, + 24, 24, 24, 24, 24, 33, 33, 33, 33, 33, 33, 33, 33, 33, 41, 41, + 41, 41, 41, 41, 41, 41, 49, 49, 49, 49, 49, 49, 49, 49, 57, 57, + 57, 57, 57, 57, 57, 57, 66, 66, 66, 66, 66, 66, 66, 66, 74, 74, + 74, 74, 74, 74, 74, 74, 74, 82, 82, 82, 82, 82, 82, 82, 82, 90, + 90, 90, 90, 90, 90, 90, 90, 99, 99, 99, 99, 99, 99, 99, 99, 107, + 107, 107, 107, 107, 107, 107, 107, 107, 115, 115, 115, 115, 115, 115, 115, 115, + 123, 123, 123, 123, 123, 123, 123, 123, 132, 132, 132, 132, 132, 132, 132, 132, + 140, 140, 140, 140, 140, 140, 140, 140, 148, 148, 148, 148, 148, 148, 148, 148, + 148, 156, 156, 156, 156, 156, 156, 156, 156, 165, 165, 165, 165, 165, 165, 165, + 165, 173, 173, 173, 173, 173, 173, 173, 173, 181, 181, 181, 181, 181, 181, 181, + 181, 181, 189, 189, 189, 189, 189, 189, 189, 189, 198, 198, 198, 198, 198, 198, + 198, 198, 206, 206, 206, 206, 206, 206, 206, 206, 214, 214, 214, 214, 214, 214, + 214, 214, 222, 222, 222, 222, 222, 222, 222, 222, 222, 231, 231, 231, 231, 231, + 231, 231, 231, 239, 239, 239, 239, 239, 239, 239, 239, 247, 247, 247, 247, 247, + 247, 247, 247, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, +}; +static const unsigned char stb__QuantGTab[256 + 16] = { + 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 4, 4, 4, 8, + 8, 8, 8, 12, 12, 12, 12, 16, 16, 16, 16, 20, 20, 20, 20, 24, + 24, 24, 24, 28, 28, 28, 28, 32, 32, 32, 32, 36, 36, 36, 36, 40, + 40, 40, 40, 44, 44, 44, 44, 48, 48, 48, 48, 52, 52, 52, 52, 56, + 56, 56, 56, 60, 60, 60, 60, 65, 65, 65, 65, 69, 69, 69, 69, 73, + 73, 73, 73, 77, 77, 77, 77, 81, 81, 81, 81, 85, 85, 85, 85, 85, + 89, 89, 89, 89, 93, 93, 93, 93, 97, 97, 97, 97, 101, 101, 101, 101, + 105, 105, 105, 105, 109, 109, 109, 109, 113, 113, 113, 113, 117, 117, 117, 117, + 121, 121, 121, 121, 125, 125, 125, 125, 130, 130, 130, 130, 134, 134, 134, 134, + 138, 138, 138, 138, 142, 142, 142, 142, 146, 146, 146, 146, 150, 150, 150, 150, + 154, 154, 154, 154, 158, 158, 158, 158, 162, 162, 162, 162, 166, 166, 166, 166, + 170, 170, 170, 170, 170, 174, 174, 174, 174, 178, 178, 178, 178, 182, 182, 182, + 182, 186, 186, 186, 186, 190, 190, 190, 190, 195, 195, 195, 195, 199, 199, 199, + 199, 203, 203, 203, 203, 207, 207, 207, 207, 211, 211, 211, 211, 215, 215, 215, + 215, 219, 219, 219, 219, 223, 223, 223, 223, 227, 227, 227, 227, 231, 231, 231, + 231, 235, 235, 235, 235, 239, 239, 239, 239, 243, 243, 243, 243, 247, 247, 247, + 247, 251, 251, 251, 251, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, +}; +static const unsigned char stb__OMatch5[256][2] = { + { 0, 0 }, { 0, 0 }, { 0, 1 }, { 0, 1 }, { 1, 0 }, { 1, 0 }, { 1, 0 }, { 1, 1 }, + { 1, 1 }, { 2, 0 }, { 2, 0 }, { 0, 4 }, { 2, 1 }, { 2, 1 }, { 2, 1 }, { 3, 0 }, + { 3, 0 }, { 3, 0 }, { 3, 1 }, { 1, 5 }, { 3, 2 }, { 3, 2 }, { 4, 0 }, { 4, 0 }, + { 4, 1 }, { 4, 1 }, { 4, 2 }, { 4, 2 }, { 4, 2 }, { 3, 5 }, { 5, 1 }, { 5, 1 }, + { 5, 2 }, { 4, 4 }, { 5, 3 }, { 5, 3 }, { 5, 3 }, { 6, 2 }, { 6, 2 }, { 6, 2 }, + { 6, 3 }, { 5, 5 }, { 6, 4 }, { 6, 4 }, { 4, 8 }, { 7, 3 }, { 7, 3 }, { 7, 3 }, + { 7, 4 }, { 7, 4 }, { 7, 4 }, { 7, 5 }, { 5, 9 }, { 7, 6 }, { 7, 6 }, { 8, 4 }, + { 8, 4 }, { 8, 5 }, { 8, 5 }, { 8, 6 }, { 8, 6 }, { 8, 6 }, { 7, 9 }, { 9, 5 }, + { 9, 5 }, { 9, 6 }, { 8, 8 }, { 9, 7 }, { 9, 7 }, { 9, 7 }, { 10, 6 }, { 10, 6 }, + { 10, 6 }, { 10, 7 }, { 9, 9 }, { 10, 8 }, { 10, 8 }, { 8, 12 }, { 11, 7 }, { 11, 7 }, + { 11, 7 }, { 11, 8 }, { 11, 8 }, { 11, 8 }, { 11, 9 }, { 9, 13 }, { 11, 10 }, { 11, 10 }, + { 12, 8 }, { 12, 8 }, { 12, 9 }, { 12, 9 }, { 12, 10 }, { 12, 10 }, { 12, 10 }, { 11, 13 }, + { 13, 9 }, { 13, 9 }, { 13, 10 }, { 12, 12 }, { 13, 11 }, { 13, 11 }, { 13, 11 }, { 14, 10 }, + { 14, 10 }, { 14, 10 }, { 14, 11 }, { 13, 13 }, { 14, 12 }, { 14, 12 }, { 12, 16 }, { 15, 11 }, + { 15, 11 }, { 15, 11 }, { 15, 12 }, { 15, 12 }, { 15, 12 }, { 15, 13 }, { 13, 17 }, { 15, 14 }, + { 15, 14 }, { 16, 12 }, { 16, 12 }, { 16, 13 }, { 16, 13 }, { 16, 14 }, { 16, 14 }, { 16, 14 }, + { 15, 17 }, { 17, 13 }, { 17, 13 }, { 17, 14 }, { 16, 16 }, { 17, 15 }, { 17, 15 }, { 17, 15 }, + { 18, 14 }, { 18, 14 }, { 18, 14 }, { 18, 15 }, { 17, 17 }, { 18, 16 }, { 18, 16 }, { 16, 20 }, + { 19, 15 }, { 19, 15 }, { 19, 15 }, { 19, 16 }, { 19, 16 }, { 19, 16 }, { 19, 17 }, { 17, 21 }, + { 19, 18 }, { 19, 18 }, { 20, 16 }, { 20, 16 }, { 20, 17 }, { 20, 17 }, { 20, 18 }, { 20, 18 }, + { 20, 18 }, { 19, 21 }, { 21, 17 }, { 21, 17 }, { 21, 18 }, { 20, 20 }, { 21, 19 }, { 21, 19 }, + { 21, 19 }, { 22, 18 }, { 22, 18 }, { 22, 18 }, { 22, 19 }, { 21, 21 }, { 22, 20 }, { 22, 20 }, + { 20, 24 }, { 23, 19 }, { 23, 19 }, { 23, 19 }, { 23, 20 }, { 23, 20 }, { 23, 20 }, { 23, 21 }, + { 21, 25 }, { 23, 22 }, { 23, 22 }, { 24, 20 }, { 24, 20 }, { 24, 21 }, { 24, 21 }, { 24, 22 }, + { 24, 22 }, { 24, 22 }, { 23, 25 }, { 25, 21 }, { 25, 21 }, { 25, 22 }, { 24, 24 }, { 25, 23 }, + { 25, 23 }, { 25, 23 }, { 26, 22 }, { 26, 22 }, { 26, 22 }, { 26, 23 }, { 25, 25 }, { 26, 24 }, + { 26, 24 }, { 24, 28 }, { 27, 23 }, { 27, 23 }, { 27, 23 }, { 27, 24 }, { 27, 24 }, { 27, 24 }, + { 27, 25 }, { 25, 29 }, { 27, 26 }, { 27, 26 }, { 28, 24 }, { 28, 24 }, { 28, 25 }, { 28, 25 }, + { 28, 26 }, { 28, 26 }, { 28, 26 }, { 27, 29 }, { 29, 25 }, { 29, 25 }, { 29, 26 }, { 28, 28 }, + { 29, 27 }, { 29, 27 }, { 29, 27 }, { 30, 26 }, { 30, 26 }, { 30, 26 }, { 30, 27 }, { 29, 29 }, + { 30, 28 }, { 30, 28 }, { 30, 28 }, { 31, 27 }, { 31, 27 }, { 31, 27 }, { 31, 28 }, { 31, 28 }, + { 31, 28 }, { 31, 29 }, { 31, 29 }, { 31, 30 }, { 31, 30 }, { 31, 30 }, { 31, 31 }, { 31, 31 }, +}; +static const unsigned char stb__OMatch6[256][2] = { + { 0, 0 }, { 0, 1 }, { 1, 0 }, { 1, 0 }, { 1, 1 }, { 2, 0 }, { 2, 1 }, { 3, 0 }, + { 3, 0 }, { 3, 1 }, { 4, 0 }, { 4, 0 }, { 4, 1 }, { 5, 0 }, { 5, 1 }, { 6, 0 }, + { 6, 0 }, { 6, 1 }, { 7, 0 }, { 7, 0 }, { 7, 1 }, { 8, 0 }, { 8, 1 }, { 8, 1 }, + { 8, 2 }, { 9, 1 }, { 9, 2 }, { 9, 2 }, { 9, 3 }, { 10, 2 }, { 10, 3 }, { 10, 3 }, + { 10, 4 }, { 11, 3 }, { 11, 4 }, { 11, 4 }, { 11, 5 }, { 12, 4 }, { 12, 5 }, { 12, 5 }, + { 12, 6 }, { 13, 5 }, { 13, 6 }, { 8, 16 }, { 13, 7 }, { 14, 6 }, { 14, 7 }, { 9, 17 }, + { 14, 8 }, { 15, 7 }, { 15, 8 }, { 11, 16 }, { 15, 9 }, { 15, 10 }, { 16, 8 }, { 16, 9 }, + { 16, 10 }, { 15, 13 }, { 17, 9 }, { 17, 10 }, { 17, 11 }, { 15, 16 }, { 18, 10 }, { 18, 11 }, + { 18, 12 }, { 16, 16 }, { 19, 11 }, { 19, 12 }, { 19, 13 }, { 17, 17 }, { 20, 12 }, { 20, 13 }, + { 20, 14 }, { 19, 16 }, { 21, 13 }, { 21, 14 }, { 21, 15 }, { 20, 17 }, { 22, 14 }, { 22, 15 }, + { 25, 10 }, { 22, 16 }, { 23, 15 }, { 23, 16 }, { 26, 11 }, { 23, 17 }, { 24, 16 }, { 24, 17 }, + { 27, 12 }, { 24, 18 }, { 25, 17 }, { 25, 18 }, { 28, 13 }, { 25, 19 }, { 26, 18 }, { 26, 19 }, + { 29, 14 }, { 26, 20 }, { 27, 19 }, { 27, 20 }, { 30, 15 }, { 27, 21 }, { 28, 20 }, { 28, 21 }, + { 28, 21 }, { 28, 22 }, { 29, 21 }, { 29, 22 }, { 24, 32 }, { 29, 23 }, { 30, 22 }, { 30, 23 }, + { 25, 33 }, { 30, 24 }, { 31, 23 }, { 31, 24 }, { 27, 32 }, { 31, 25 }, { 31, 26 }, { 32, 24 }, + { 32, 25 }, { 32, 26 }, { 31, 29 }, { 33, 25 }, { 33, 26 }, { 33, 27 }, { 31, 32 }, { 34, 26 }, + { 34, 27 }, { 34, 28 }, { 32, 32 }, { 35, 27 }, { 35, 28 }, { 35, 29 }, { 33, 33 }, { 36, 28 }, + { 36, 29 }, { 36, 30 }, { 35, 32 }, { 37, 29 }, { 37, 30 }, { 37, 31 }, { 36, 33 }, { 38, 30 }, + { 38, 31 }, { 41, 26 }, { 38, 32 }, { 39, 31 }, { 39, 32 }, { 42, 27 }, { 39, 33 }, { 40, 32 }, + { 40, 33 }, { 43, 28 }, { 40, 34 }, { 41, 33 }, { 41, 34 }, { 44, 29 }, { 41, 35 }, { 42, 34 }, + { 42, 35 }, { 45, 30 }, { 42, 36 }, { 43, 35 }, { 43, 36 }, { 46, 31 }, { 43, 37 }, { 44, 36 }, + { 44, 37 }, { 44, 37 }, { 44, 38 }, { 45, 37 }, { 45, 38 }, { 40, 48 }, { 45, 39 }, { 46, 38 }, + { 46, 39 }, { 41, 49 }, { 46, 40 }, { 47, 39 }, { 47, 40 }, { 43, 48 }, { 47, 41 }, { 47, 42 }, + { 48, 40 }, { 48, 41 }, { 48, 42 }, { 47, 45 }, { 49, 41 }, { 49, 42 }, { 49, 43 }, { 47, 48 }, + { 50, 42 }, { 50, 43 }, { 50, 44 }, { 48, 48 }, { 51, 43 }, { 51, 44 }, { 51, 45 }, { 49, 49 }, + { 52, 44 }, { 52, 45 }, { 52, 46 }, { 51, 48 }, { 53, 45 }, { 53, 46 }, { 53, 47 }, { 52, 49 }, + { 54, 46 }, { 54, 47 }, { 57, 42 }, { 54, 48 }, { 55, 47 }, { 55, 48 }, { 58, 43 }, { 55, 49 }, + { 56, 48 }, { 56, 49 }, { 59, 44 }, { 56, 50 }, { 57, 49 }, { 57, 50 }, { 60, 45 }, { 57, 51 }, + { 58, 50 }, { 58, 51 }, { 61, 46 }, { 58, 52 }, { 59, 51 }, { 59, 52 }, { 62, 47 }, { 59, 53 }, + { 60, 52 }, { 60, 53 }, { 60, 53 }, { 60, 54 }, { 61, 53 }, { 61, 54 }, { 61, 54 }, { 61, 55 }, + { 62, 54 }, { 62, 55 }, { 62, 55 }, { 62, 56 }, { 63, 55 }, { 63, 56 }, { 63, 56 }, { 63, 57 }, + { 63, 58 }, { 63, 59 }, { 63, 59 }, { 63, 60 }, { 63, 61 }, { 63, 62 }, { 63, 62 }, { 63, 63 }, +}; static int stb__Mul8Bit(int a, int b) { @@ -117,9 +214,10 @@ static void stb__From16Bit(unsigned char *out, unsigned short v) int gv = (v & 0x07e0) >> 5; int bv = (v & 0x001f) >> 0; - out[0] = stb__Expand5[rv]; - out[1] = stb__Expand6[gv]; - out[2] = stb__Expand5[bv]; + // expand to 8 bits via bit replication + out[0] = (rv * 33) >> 2; + out[1] = (gv * 65) >> 4; + out[2] = (bv * 33) >> 2; out[3] = 0; } @@ -151,35 +249,6 @@ static void stb__Lerp13RGB(unsigned char *out, unsigned char *p1, unsigned char /****************************************************************************/ -// compute table to reproduce constant colors as accurately as possible -static void stb__PrepareOptTable(unsigned char *Table,const unsigned char *expand,int size) -{ - int i,mn,mx; - for (i=0;i<256;i++) { - int bestErr = 256; - for (mn=0;mn> 4)]; @@ -316,7 +385,7 @@ static unsigned int stb__MatchColorsBlock(unsigned char *block, unsigned char *c // The color optimization function. (Clever code, part 1) static void stb__OptimizeColorsBlock(unsigned char *block, unsigned short *pmax16, unsigned short *pmin16) { - int mind = 0x7fffffff,maxd = -0x7fffffff; + int mind,maxd; unsigned char *minp, *maxp; double magn; int v_r,v_g,v_b; @@ -398,8 +467,10 @@ static void stb__OptimizeColorsBlock(unsigned char *block, unsigned short *pmax1 v_b = (int) (vfb * magn); } + minp = maxp = block; + mind = maxd = block[0]*v_r + block[1]*v_g + block[2]*v_b; // Pick colors at extreme points - for(i=0;i<16;i++) + for(i=1;i<16;i++) { int dot = block[i*4+0]*v_r + block[i*4+1]*v_g + block[i*4+2]*v_b; @@ -418,12 +489,12 @@ static void stb__OptimizeColorsBlock(unsigned char *block, unsigned short *pmax1 *pmin16 = stb__As16Bit(minp[0],minp[1],minp[2]); } -static const float midpoints5[32] = { +static const float stb__midpoints5[32] = { 0.015686f, 0.047059f, 0.078431f, 0.111765f, 0.145098f, 0.176471f, 0.207843f, 0.241176f, 0.274510f, 0.305882f, 0.337255f, 0.370588f, 0.403922f, 0.435294f, 0.466667f, 0.5f, 0.533333f, 0.564706f, 0.596078f, 0.629412f, 0.662745f, 0.694118f, 0.725490f, 0.758824f, 0.792157f, 0.823529f, 0.854902f, 0.888235f, 0.921569f, 0.952941f, 0.984314f, 1.0f }; -static const float midpoints6[64] = { +static const float stb__midpoints6[64] = { 0.007843f, 0.023529f, 0.039216f, 0.054902f, 0.070588f, 0.086275f, 0.101961f, 0.117647f, 0.133333f, 0.149020f, 0.164706f, 0.180392f, 0.196078f, 0.211765f, 0.227451f, 0.245098f, 0.262745f, 0.278431f, 0.294118f, 0.309804f, 0.325490f, 0.341176f, 0.356863f, 0.372549f, 0.388235f, 0.403922f, 0.419608f, 0.435294f, 0.450980f, 0.466667f, 0.482353f, 0.500000f, 0.517647f, 0.533333f, 0.549020f, 0.564706f, 0.580392f, 0.596078f, 0.611765f, 0.627451f, 0.643137f, 0.658824f, 0.674510f, 0.690196f, 0.705882f, 0.721569f, 0.737255f, 0.754902f, @@ -435,7 +506,7 @@ static unsigned short stb__Quantize5(float x) unsigned short q; x = x < 0 ? 0 : x > 1 ? 1 : x; // saturate q = (unsigned short)(x * 31); - q += (x > midpoints5[q]); + q += (x > stb__midpoints5[q]); return q; } @@ -444,7 +515,7 @@ static unsigned short stb__Quantize6(float x) unsigned short q; x = x < 0 ? 0 : x > 1 ? 1 : x; // saturate q = (unsigned short)(x * 63); - q += (x > midpoints6[q]); + q += (x > stb__midpoints6[q]); return q; } @@ -654,35 +725,9 @@ static void stb__CompressAlphaBlock(unsigned char *dest,unsigned char *src, int } } -static void stb__InitDXT() -{ - int i; - for(i=0;i<32;i++) - stb__Expand5[i] = (unsigned char)((i<<3)|(i>>2)); - - for(i=0;i<64;i++) - stb__Expand6[i] = (unsigned char)((i<<2)|(i>>4)); - - for(i=0;i<256+16;i++) - { - int v = i-8 < 0 ? 0 : i-8 > 255 ? 255 : i-8; - stb__QuantRBTab[i] = stb__Expand5[stb__Mul8Bit(v,31)]; - stb__QuantGTab[i] = stb__Expand6[stb__Mul8Bit(v,63)]; - } - - stb__PrepareOptTable(&stb__OMatch5[0][0],stb__Expand5,32); - stb__PrepareOptTable(&stb__OMatch6[0][0],stb__Expand6,64); -} - void stb_compress_dxt_block(unsigned char *dest, const unsigned char *src, int alpha, int mode) { unsigned char data[16][4]; - static int init=1; - if (init) { - stb__InitDXT(); - init=0; - } - if (alpha) { int i; stb__CompressAlphaBlock(dest,(unsigned char*) src+3, 4); @@ -710,6 +755,76 @@ void stb_compress_bc5_block(unsigned char *dest, const unsigned char *src) } #endif // STB_DXT_IMPLEMENTATION +// Compile with STB_DXT_IMPLEMENTATION and STB_DXT_GENERATE_TABLES +// defined to generate the tables above. +#ifdef STB_DXT_GENERATE_TABLES +#include + +int main() +{ + int i, j; + const char *quant_names[] = { "stb__QuantRBTab", "stb__QuantGTab" }; + const char *omatch_names[] = { "stb__OMatch5", "stb__OMatch6" }; + int dequant_mults[2] = { 33*4, 65 }; // .4 fixed-point dequant multipliers + + // quant tables (for dither) + for (i=0; i < 2; ++i) { + int quant_mult = i ? 63 : 31; + printf("static const unsigned char %s[256 + 16] = {\n", quant_names[i]); + for (int j = 0; j < 256 + 16; ++j) { + int v = j - 8; + int q, dq; + + v = (v < 0) ? 0 : (v > 255) ? 255 : v; // clamp + q = stb__Mul8Bit(v, quant_mult); // quantize + dq = (q * dequant_mults[i]) >> 4; // dequantize + + if ((j % 16) == 0) printf(" "); // 2 spaces, third is done below + printf(" %3d,", dq); + if ((j % 16) == 15) printf("\n"); + } + printf("};\n"); + } + + // optimal endpoint tables + for (i = 0; i < 2; ++i) { + int dequant = dequant_mults[i]; + int size = i ? 64 : 32; + printf("static const unsigned char %s[256][2] = {\n", omatch_names[i]); + for (int j = 0; j < 256; ++j) { + int mn, mx; + int best_mn = 0, best_mx = 0; + int best_err = 256; + for (mn=0;mn> 4; + int maxe = (mx * dequant) >> 4; + int err = abs(stb__Lerp13(maxe, mine) - j); + + // DX10 spec says that interpolation must be within 3% of "correct" result, + // add this as error term. Normally we'd expect a random distribution of + // +-1.5% error, but nowhere in the spec does it say that the error has to be + // unbiased - better safe than sorry. + err += abs(maxe - mine) * 3 / 100; + + if(err < best_err) { + best_mn = mn; + best_mx = mx; + best_err = err; + } + } + } + if ((j % 8) == 0) printf(" "); // 2 spaces, third is done below + printf(" { %2d, %2d },", best_mx, best_mn); + if ((j % 8) == 7) printf("\n"); + } + printf("};\n"); + } + + return 0; +} +#endif + /* ------------------------------------------------------------------------------ This software is available under 2 licenses -- choose whichever you prefer.