Function MipCoordFromBase

qrenderdoc/Windows/TextureViewer.cpp:61–77

// once

static inline uint32_t MipCoordFromBase(const uint32_t coord, const uint32_t mip, const uint32_t dim)
{
  const uint32_t mipDim = (dim >> mip) > 0 ? (dim >> mip) : 1;

  // for mip levels where we more than half (e.g. 15x15 to 7x7) the coord can't be shifted by the
  // mip.
  // e.g. if the top level is 960x540 an x coordinate of 950 would be shifted by 7 down to 7, but
  // mip 7 is 7x4 so the max x co-ordinate is 6. Instead we need to get the float value on the top
  // mip, multiply by the mip dimension, and floor it

  const float coordf = float(coord) / float(dim);

  // we add 1e-6 to account for float errors, where we might not get back coord after rounding down
  // in the coordf calculation even when mipDim == dim. This will not affect the rounding for any
  // realistic texture sizes - even for a dim of 16383 and coord of 16382
  return uint32_t(mipDim * (coordf + 1e-6f));
}

static inline uint32_t BaseCoordFromMip(uint32_t coord, const uint32_t mip, const uint32_t dim)
{