Add comment to explain calculation.

2020-04-02 14:14:13 +00:00
parent ccf3532eb2
commit 72907566bb
1 changed files with 10 additions and 0 deletions
@@ -139,6 +139,16 @@ class Triangulation {
    const sourceBottomRight = this.transformInv_(destinationBottomRight);
    const sourceBottomLeft = this.transformInv_(destinationBottomLeft);
    /*
     * The maxSubdivision controls how many splittings of the target area can
     * be done. The idea here is to do a linear mapping of the target areas
     * but the actual overal reprojection (can be) extremely non-linear. The
     * default value of MAX_SUBDIVISION was chosen based on mapping a 256x256
     * tile size. However this function is also called to remap canvas rendered
     * layers which can be much larger. This calculation increases the maxSubdivision
     * value by the right factor so that each 256x256 pixel area has
     * MAX_SUBDIVISION divisions.
     */
    const maxSubdivision = MAX_SUBDIVISION + (opt_destinationResolution ?
      Math.max(0, Math.ceil(Math.log2(getArea(targetExtent) /
        (opt_destinationResolution * opt_destinationResolution * 256 * 256))))