+ if(min_length < MipMapScaleFactor)
+ {
+ // Search individual samples up to the beginning of
+ // the next first level mip map block
+ const uint64_t final_sample = min(end,
+ pow2_ceil(index, MipMapScalePower));
+
+ for(index;
+ index < final_sample &&
+ (index & ~(~0 << MipMapScalePower)) != 0;
+ index++)
+ {
+ const bool sample =
+ (get_sample(index) & sig_mask) != 0;
+ if(sample != last_sample)
+ break;
+ }
+ }
+ else
+ {
+ // If resolution is less than a mip map block,
+ // round up to the beginning of the mip-map block
+ // for this level of detail
+ const int min_level_scale_power =
+ (level + 1) * MipMapScalePower;
+ index = pow2_ceil(index, min_level_scale_power);
+ }
+
+ // Slide right and zoom out at the beginnings of mip-map
+ // blocks until we encounter a change
+ while(1)
+ {
+ const int level_scale_power =
+ (level + 1) * MipMapScalePower;
+ const uint64_t offset = index >> level_scale_power;
+ assert(offset >= 0);
+
+ // Check if we reached the last block at this level,
+ // or if there was a change in this block
+ if(offset >= _mip_map[level].length ||
+ (*(uint64_t*)((uint8_t*)_mip_map[level].data +
+ _unit_size * offset) & sig_mask))
+ break;
+
+ if((offset & ~(~0 << MipMapScalePower)) == 0)
+ {
+ // If we are now at the beginning of a higher
+ // level mip-map block ascend one level
+ if(!_mip_map[level + 1].data)
+ break;
+
+ level++;
+ }
+ else
+ {
+ // Slide right to the beginning of the next mip
+ // map block
+ index = pow2_ceil(index, level_scale_power);
+ }
+ }
+
+ // Zoom in, and slide right until we encounter a change,
+ // and repeat until we reach min_level
+ while(1)
+ {
+ assert(_mip_map[level].data);
+
+ const int level_scale_power =
+ (level + 1) * MipMapScalePower;
+ const uint64_t offset = index >> level_scale_power;
+ assert(offset >= 0);
+
+ // Check if we reached the last block at this level,
+ // or if there was a change in this block
+ if(offset >= _mip_map[level].length ||
+ (*(uint64_t*)((uint8_t*)_mip_map[level].data +
+ _unit_size * offset) & sig_mask))
+ {
+ // Zoom in unless we reached the minimum zoom
+ if(level == min_level)
+ break;
+
+ level--;
+ }
+ else
+ {
+ // Slide right to the beginning of the next mip map block
+ index = pow2_ceil(index, level_scale_power);
+ }
+ }
+
+ // If individual samples within the limit of resolution,
+ // do a linear search for the next transition within the block
+ if(min_length < MipMapScaleFactor)
+ {
+ for(index; index < end; index++)
+ {
+ const bool sample =
+ (get_sample(index) & sig_mask) != 0;
+ if(sample != last_sample)
+ break;
+ }
+ }
+
+ if(index < end)