geom/m46402: sixteen entry occupancy context map update table

Replaces the existing map update tables (generated from (L*p+s)/(L+1),
memory L=10) with an adaptive memory (L=max(5, 1/p, 1/(1-p)) clipped
to 200) represented as delta transitions and quantised to 16 entries.

tmc3/geometry_octree.h

@@ -194,9 +194,9 @@ CtxMapOctreeOccupancy::evolve(bool bit, uint8_t* ctxIdx)
   uint8_t retval = *ctxIdx;
 
   if (bit)
-    *ctxIdx = kCtxMapOctreeOccupancyEvolutionOn1[*ctxIdx];
+    *ctxIdx += kCtxMapOctreeOccupancyDelta[(255 - *ctxIdx) >> 4];
   else
-    *ctxIdx = kCtxMapOctreeOccupancyEvolutionOn0[*ctxIdx];
+    *ctxIdx -= kCtxMapOctreeOccupancyDelta[*ctxIdx >> 4];
 
   return retval;
 }

tmc3/tables.cpp

@@ -257,46 +257,9 @@ const uint8_t pcc::kOccMapRotateZ090[256] = {
 
 //============================================================================
 
-// transition tables L= 10; 256 ctx
-const uint8_t pcc::kCtxMapOctreeOccupancyEvolutionOn0[256] = {
-  0,   1,   2,   3,   4,   5,   6,   7,   8,   9,   9,   10,  11,  12,  13,
-  14,  15,  16,  17,  18,  19,  20,  21,  22,  23,  24,  25,  26,  27,  28,
-  29,  29,  30,  31,  32,  33,  34,  35,  36,  37,  38,  39,  40,  41,  42,
-  43,  44,  45,  46,  47,  48,  48,  49,  50,  51,  52,  53,  54,  55,  56,
-  57,  58,  59,  60,  61,  62,  63,  64,  65,  66,  66,  67,  68,  69,  70,
-  71,  72,  73,  74,  75,  76,  77,  78,  79,  80,  81,  82,  82,  83,  84,
-  85,  86,  87,  88,  89,  90,  91,  92,  93,  94,  95,  96,  96,  97,  98,
-  99,  100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 109, 110, 111, 112,
-  113, 114, 115, 116, 117, 118, 119, 120, 120, 121, 122, 123, 124, 125, 126,
-  127, 128, 129, 130, 130, 131, 132, 133, 134, 135, 136, 137, 138, 138, 139,
-  140, 141, 142, 143, 144, 145, 146, 146, 147, 148, 149, 150, 151, 152, 152,
-  153, 154, 155, 156, 157, 158, 158, 159, 160, 161, 162, 163, 163, 164, 165,
-  166, 167, 167, 168, 169, 170, 171, 171, 172, 173, 174, 175, 175, 176, 177,
-  178, 178, 179, 180, 181, 181, 182, 183, 183, 184, 185, 185, 186, 187, 187,
-  188, 189, 189, 190, 191, 191, 192, 192, 193, 194, 194, 195, 195, 196, 196,
-  197, 197, 198, 198, 199, 199, 199, 200, 200, 201, 201, 201, 202, 202, 202,
-  203, 203, 203, 203, 204, 204, 204, 204, 204, 204, 204, 205, 205, 205, 205,
-  205};
-
-const uint8_t pcc::kCtxMapOctreeOccupancyEvolutionOn1[256] = {
-  49,  49,  49,  49,  49,  49,  49,  49,  49,  50,  50,  50,  50,  51,  51,
-  51,  51,  52,  52,  52,  53,  53,  54,  54,  54,  55,  55,  56,  56,  57,
-  57,  58,  58,  59,  59,  60,  61,  61,  62,  62,  63,  64,  64,  65,  66,
-  66,  67,  68,  68,  69,  70,  70,  71,  72,  72,  73,  74,  75,  75,  76,
-  77,  78,  78,  79,  80,  81,  82,  82,  83,  84,  85,  86,  86,  87,  88,
-  89,  90,  90,  91,  92,  93,  94,  95,  95,  96,  97,  98,  99,  100, 101,
-  101, 102, 103, 104, 105, 106, 107, 107, 108, 109, 110, 111, 112, 113, 114,
-  115, 115, 116, 117, 118, 119, 120, 121, 122, 123, 123, 124, 125, 126, 127,
-  128, 129, 130, 131, 132, 133, 133, 134, 135, 136, 137, 138, 139, 140, 141,
-  142, 143, 144, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155,
-  156, 157, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169,
-  170, 171, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183,
-  184, 185, 186, 187, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197,
-  198, 199, 200, 201, 202, 203, 204, 205, 205, 206, 207, 208, 209, 210, 211,
-  212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 224, 225,
-  226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240,
-  241, 242, 243, 244, 245, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254,
-  255};
+// Generated from (L*p+s)/(L+1), L=min(200, max(5, 1/p, 1/(1-p))
+const uint8_t pcc::kCtxMapOctreeOccupancyDelta[16] = {
+  0, 1, 1, 2, 4, 7, 9, 11, 14, 16, 19, 23, 22, 18, 13, 6};
 
 //============================================================================
 

tmc3/tables.h

@@ -82,9 +82,9 @@ extern const uint8_t kOccMapRotateZ270[256];
 extern const uint8_t kOccMapRotateZ180[256];
 extern const uint8_t kOccMapRotateZ090[256];
 
-// todo(df): ...
-extern const uint8_t kCtxMapOctreeOccupancyEvolutionOn0[256];
-extern const uint8_t kCtxMapOctreeOccupancyEvolutionOn1[256];
+// Geometry occupancy context map update table, represented as deltas to
+// current map entry value.
+extern const uint8_t kCtxMapOctreeOccupancyDelta[16];
 
 // LUT initialisation table
 extern const uint8_t kDualLutOccupancyCoderInit[10][32];