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Verify triangulation against source/target extents

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If we do this here, we can avoid some computations on triangles that will
be unused in the future anyway + reduce problems with non-global projections
without specified extents.
This commit is contained in:
Petr Sloup
2015-05-28 15:52:04 +02:00
parent 1222287f22
commit c425b9c0e6
1 changed files with 50 additions and 26 deletions
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76
src/ol/reproj/triangulation.js
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@@ -16,25 +16,67 @@ goog.require('ol.extent');
ol.reproj.Triangulation;
/**
* Adds triangle to the triangulation (and reprojects the vertices) if valid.
* @private
* @param {ol.reproj.Triangulation} triangulation
* @param {ol.Coordinate} a
* @param {ol.Coordinate} b
* @param {ol.Coordinate} c
* @param {ol.TransformFunction} transformInv Inverse transform (dst -> src).
* @param {ol.Extent=} opt_maxTargetExtent
* @param {ol.Extent=} opt_maxSourceExtent
*/
ol.reproj.triangulation.addTriangleIfValid_ = function(triangulation, a, b, c,
transformInv, opt_maxTargetExtent, opt_maxSourceExtent) {
if (goog.isDefAndNotNull(opt_maxTargetExtent)) {
if (!ol.extent.containsCoordinate(opt_maxTargetExtent, a) &&
!ol.extent.containsCoordinate(opt_maxTargetExtent, b) &&
!ol.extent.containsCoordinate(opt_maxTargetExtent, c)) {
// whole triangle outside target projection extent -> ignore
return;
}
// clamp the vertices to the extent edges before transforming
a = ol.extent.closestCoordinate(opt_maxTargetExtent, a);
b = ol.extent.closestCoordinate(opt_maxTargetExtent, b);
c = ol.extent.closestCoordinate(opt_maxTargetExtent, c);
}
var aSrc = transformInv(a);
var bSrc = transformInv(b);
var cSrc = transformInv(c);
if (goog.isDefAndNotNull(opt_maxSourceExtent)) {
var srcTriangleExtent = ol.extent.boundingExtent([aSrc, bSrc, cSrc]);
if (!ol.extent.intersects(srcTriangleExtent, opt_maxSourceExtent)) {
// whole triangle outside source projection extent -> ignore
return;
}
}
triangulation.push([[aSrc, a], [bSrc, b], [cSrc, c]]);
};
/**
* Triangulates given extent and reprojects vertices.
* TODO: improved triangulation, better error handling of some trans fails
* @param {ol.Extent} extent
* @param {ol.TransformFunction} transformInv Inverse transform (dst -> src).
* @param {ol.Extent=} opt_maxTargetExtent
* @param {ol.Extent=} opt_maxSourceExtent
* @param {number=} opt_subdiv Subdivision factor (default 4).
* @return {ol.reproj.Triangulation}
*/
ol.reproj.triangulation.createForExtent = function(extent, transformInv,
opt_maxTargetExtent,
opt_maxSourceExtent,
opt_subdiv) {
var triangulation = [];
var tlDst = ol.extent.getTopLeft(extent);
var brDst = ol.extent.getBottomRight(extent);
var projected = {0: {}}; // cache of already transformed values
var subdiv = opt_subdiv || 4;
for (var y = 0; y < subdiv; y++) {
projected[y + 1] = {}; // prepare cache for the next line
for (var x = 0; x < subdiv; x++) {
// do 2 triangle: [(x, y), (x + 1, y + 1), (x, y + 1)]
// [(x, y), (x + 1, y), (x + 1, y + 1)]
@@ -56,30 +98,12 @@ ol.reproj.triangulation.createForExtent = function(extent, transformInv,
goog.math.lerp(tlDst[1], brDst[1], (y + 1) / subdiv)
];
if (!goog.isDef(projected[y][x])) {
projected[y][x] = transformInv(x0y0dst);
}
if (!goog.isDef(projected[y][x + 1])) {
projected[y][x + 1] = transformInv(x1y0dst);
}
if (!goog.isDef(projected[y + 1][x])) {
projected[y + 1][x] = transformInv(x0y1dst);
}
if (!goog.isDef(projected[y + 1][x + 1])) {
projected[y + 1][x + 1] = transformInv(x1y1dst);
}
triangulation.push(
[
[projected[y][x], x0y0dst],
[projected[y + 1][x + 1], x1y1dst],
[projected[y + 1][x], x0y1dst]
], [
[projected[y][x], x0y0dst],
[projected[y][x + 1], x1y0dst],
[projected[y + 1][x + 1], x1y1dst]
]
);
ol.reproj.triangulation.addTriangleIfValid_(
triangulation, x0y0dst, x1y1dst, x0y1dst,
transformInv, opt_maxTargetExtent, opt_maxSourceExtent);
ol.reproj.triangulation.addTriangleIfValid_(
triangulation, x0y0dst, x1y0dst, x1y1dst,
transformInv, opt_maxTargetExtent, opt_maxSourceExtent);
}
}