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Alternative reprojection triangulation strategy

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The quads are now subdivided more granually (to 2 instead of 4), which
usually leads to reduced number of triangles and higher performance.
This commit is contained in:
Petr Sloup
2015-08-26 18:37:18 +02:00
parent 016df5b902
commit 726bcbef83
2 changed files with 24 additions and 21 deletions
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4
src/ol/ol.js
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@@ -189,9 +189,9 @@ ol.RASTER_REPROJ_MAX_SOURCE_TILES = 100;
* @define {number} Maximum number of subdivision steps during raster
* reprojection triangulation. Prevents high memory usage and large
* number of proj4 calls when for certain transformations and areas.
* At most `2*(4^this)` triangles are created. Default is `5`.
* At most `2*(2^this)` triangles are created. Default is `10`.
*/
ol.RASTER_REPROJ_MAX_SUBDIVISION = 5;
ol.RASTER_REPROJ_MAX_SUBDIVISION = 10;
/**

41
src/ol/reproj/triangulation.js
View File

@@ -185,10 +185,10 @@ ol.reproj.Triangulation.prototype.addQuadIfValid_ = function(a, b, c, d,
}
if (maxSubdiv > 0) {
var center = [(a[0] + c[0]) / 2, (a[1] + c[1]) / 2];
var centerSrc = this.transformInv_(center);
if (!needsSubdivision) {
var center = [(a[0] + c[0]) / 2, (a[1] + c[1]) / 2];
var centerSrc = this.transformInv_(center);
var dx;
if (wrapsX) {
goog.asserts.assert(!goog.isNull(this.sourceWorldWidth_));
@@ -205,24 +205,27 @@ ol.reproj.Triangulation.prototype.addQuadIfValid_ = function(a, b, c, d,
needsSubdivision = centerSrcErrorSquared > this.errorThresholdSquared_;
}
if (needsSubdivision) {
var ab = [(a[0] + b[0]) / 2, (a[1] + b[1]) / 2];
var abSrc = this.transformInv_(ab);
var bc = [(b[0] + c[0]) / 2, (b[1] + c[1]) / 2];
var bcSrc = this.transformInv_(bc);
var cd = [(c[0] + d[0]) / 2, (c[1] + d[1]) / 2];
var cdSrc = this.transformInv_(cd);
var da = [(d[0] + a[0]) / 2, (d[1] + a[1]) / 2];
var daSrc = this.transformInv_(da);
if (Math.abs(a[0] - c[0]) <= Math.abs(a[1] - c[1])) {
var bc = [(b[0] + c[0]) / 2, (b[1] + c[1]) / 2];
var bcSrc = this.transformInv_(bc);
var da = [(d[0] + a[0]) / 2, (d[1] + a[1]) / 2];
var daSrc = this.transformInv_(da);
this.addQuadIfValid_(a, ab, center, da,
aSrc, abSrc, centerSrc, daSrc, maxSubdiv - 1);
this.addQuadIfValid_(ab, b, bc, center,
abSrc, bSrc, bcSrc, centerSrc, maxSubdiv - 1);
this.addQuadIfValid_(center, bc, c, cd,
centerSrc, bcSrc, cSrc, cdSrc, maxSubdiv - 1);
this.addQuadIfValid_(da, center, cd, d,
daSrc, centerSrc, cdSrc, dSrc, maxSubdiv - 1);
this.addQuadIfValid_(a, b, bc, da,
aSrc, bSrc, bcSrc, daSrc, maxSubdiv - 1);
this.addQuadIfValid_(da, bc, c, d,
daSrc, bcSrc, cSrc, dSrc, maxSubdiv - 1);
} else {
var ab = [(a[0] + b[0]) / 2, (a[1] + b[1]) / 2];
var abSrc = this.transformInv_(ab);
var cd = [(c[0] + d[0]) / 2, (c[1] + d[1]) / 2];
var cdSrc = this.transformInv_(cd);
this.addQuadIfValid_(a, ab, cd, d,
aSrc, abSrc, cdSrc, dSrc, maxSubdiv - 1);
this.addQuadIfValid_(ab, b, c, cd,
abSrc, bSrc, cSrc, cdSrc, maxSubdiv - 1);
}
return;
}
}