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https://github.com/mapbox/tippecanoe.git
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Let Clipper clean up polygons again after scaling and simplification
This commit is contained in:
Eric Fischer
parent
6a1895547d
commit
f64e2c94e2
174
geometry.cc
174
geometry.cc
@ -207,124 +207,6 @@ drawvec shrink_lines(drawvec &geom, int z, int detail, int basezoom, long long *
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}
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#endif
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#if 0
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static bool inside(draw d, int edge, long long area, long long buffer) {
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long long clip_buffer = buffer * area / 256;
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switch (edge) {
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case 0: // top
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return d.y > -clip_buffer;
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case 1: // right
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return d.x < area + clip_buffer;
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case 2: // bottom
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return d.y < area + clip_buffer;
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case 3: // left
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return d.x > -clip_buffer;
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}
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fprintf(stderr, "internal error inside\n");
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exit(EXIT_FAILURE);
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}
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// http://stackoverflow.com/questions/563198/how-do-you-detect-where-two-line-segments-intersect
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static draw get_line_intersection(draw p0, draw p1, draw p2, draw p3) {
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double s1_x = p1.x - p0.x;
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double s1_y = p1.y - p0.y;
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double s2_x = p3.x - p2.x;
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double s2_y = p3.y - p2.y;
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double t;
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// s = (-s1_y * (p0.x - p2.x) + s1_x * (p0.y - p2.y)) / (-s2_x * s1_y + s1_x * s2_y);
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t = (s2_x * (p0.y - p2.y) - s2_y * (p0.x - p2.x)) / (-s2_x * s1_y + s1_x * s2_y);
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return draw(VT_LINETO, p0.x + (t * s1_x), p0.y + (t * s1_y));
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}
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static draw intersect(draw a, draw b, int edge, long long area, long long buffer) {
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long long clip_buffer = buffer * area / 256;
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switch (edge) {
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case 0: // top
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return get_line_intersection(a, b, draw(VT_MOVETO, -clip_buffer, -clip_buffer), draw(VT_MOVETO, area + clip_buffer, -clip_buffer));
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break;
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case 1: // right
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return get_line_intersection(a, b, draw(VT_MOVETO, area + clip_buffer, -clip_buffer), draw(VT_MOVETO, area + clip_buffer, area + clip_buffer));
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break;
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case 2: // bottom
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return get_line_intersection(a, b, draw(VT_MOVETO, area + clip_buffer, area + clip_buffer), draw(VT_MOVETO, -clip_buffer, area + clip_buffer));
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break;
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case 3: // left
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return get_line_intersection(a, b, draw(VT_MOVETO, -clip_buffer, area + clip_buffer), draw(VT_MOVETO, -clip_buffer, -clip_buffer));
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break;
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}
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fprintf(stderr, "internal error intersecting\n");
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exit(EXIT_FAILURE);
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}
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// http://en.wikipedia.org/wiki/Sutherland%E2%80%93Hodgman_algorithm
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static drawvec clip_poly1(drawvec &geom, int z, int detail, int buffer) {
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drawvec out = geom;
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long long area = 0xFFFFFFFF;
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if (z != 0) {
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area = 1LL << (32 - z);
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}
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for (int edge = 0; edge < 4; edge++) {
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if (out.size() > 0) {
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drawvec in = out;
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out.resize(0);
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draw S = in[in.size() - 1];
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for (unsigned e = 0; e < in.size(); e++) {
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draw E = in[e];
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if (inside(E, edge, area, buffer)) {
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if (!inside(S, edge, area, buffer)) {
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out.push_back(intersect(S, E, edge, area, buffer));
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}
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out.push_back(E);
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} else if (inside(S, edge, area, buffer)) {
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out.push_back(intersect(S, E, edge, area, buffer));
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}
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S = E;
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}
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}
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}
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if (out.size() > 0) {
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// If the polygon begins and ends outside the edge,
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// the starting and ending points will be left as the
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// places where it intersects the edge. Need to add
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// another point to close the loop.
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if (out[0].x != out[out.size() - 1].x || out[0].y != out[out.size() - 1].y) {
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out.push_back(out[0]);
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}
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if (out.size() < 3) {
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fprintf(stderr, "Polygon degenerated to a line segment\n");
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}
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out[0].op = VT_MOVETO;
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for (unsigned i = 1; i < out.size(); i++) {
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out[i].op = VT_LINETO;
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}
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}
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return out;
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}
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#endif
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static void decode_clipped(ClipperLib::PolyNode *t, drawvec &out) {
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// To make the GeoJSON come out right, we need to do each of the
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// outer rings followed by its children if any, and then go back
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@ -355,7 +237,7 @@ static void decode_clipped(ClipperLib::PolyNode *t, drawvec &out) {
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}
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}
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drawvec clip_poly(drawvec &geom, int z, int detail, int buffer) {
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drawvec clean_or_clip_poly(drawvec &geom, int z, int detail, int buffer, bool clip) {
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ClipperLib::Clipper clipper(ClipperLib::ioStrictlySimple);
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for (unsigned i = 0; i < geom.size(); i++) {
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@ -375,11 +257,13 @@ drawvec clip_poly(drawvec &geom, int z, int detail, int buffer) {
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}
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if (!clipper.AddPath(path, ClipperLib::ptSubject, true)) {
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#if 0
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fprintf(stderr, "Couldn't add polygon for clipping:");
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for (unsigned k = i; k < j; k++) {
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fprintf(stderr, " %lld,%lld", geom[k].x, geom[k].y);
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}
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fprintf(stderr, "\n");
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#endif
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}
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i = j - 1;
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@ -389,24 +273,32 @@ drawvec clip_poly(drawvec &geom, int z, int detail, int buffer) {
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}
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}
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long long area = 0xFFFFFFFF;
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if (z != 0) {
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area = 1LL << (32 - z);
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if (clip) {
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long long area = 0xFFFFFFFF;
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if (z != 0) {
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area = 1LL << (32 - z);
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}
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long long clip_buffer = buffer * area / 256;
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ClipperLib::Path edge;
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edge.push_back(ClipperLib::IntPoint(-clip_buffer, -clip_buffer));
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edge.push_back(ClipperLib::IntPoint(area + clip_buffer, -clip_buffer));
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edge.push_back(ClipperLib::IntPoint(area + clip_buffer, area + clip_buffer));
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edge.push_back(ClipperLib::IntPoint(-clip_buffer, area + clip_buffer));
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edge.push_back(ClipperLib::IntPoint(-clip_buffer, -clip_buffer));
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clipper.AddPath(edge, ClipperLib::ptClip, true);
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}
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long long clip_buffer = buffer * area / 256;
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ClipperLib::Path edge;
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edge.push_back(ClipperLib::IntPoint(-clip_buffer, -clip_buffer));
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edge.push_back(ClipperLib::IntPoint(area + clip_buffer, -clip_buffer));
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edge.push_back(ClipperLib::IntPoint(area + clip_buffer, area + clip_buffer));
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edge.push_back(ClipperLib::IntPoint(-clip_buffer, area + clip_buffer));
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edge.push_back(ClipperLib::IntPoint(-clip_buffer, -clip_buffer));
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clipper.AddPath(edge, ClipperLib::ptClip, true);
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ClipperLib::PolyTree clipped;
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if (!clipper.Execute(ClipperLib::ctIntersection, clipped)) {
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fprintf(stderr, "Polygon clip failed\n");
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if (clip) {
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if (!clipper.Execute(ClipperLib::ctIntersection, clipped)) {
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fprintf(stderr, "Polygon clip failed\n");
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}
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} else {
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if (!clipper.Execute(ClipperLib::ctUnion, clipped)) {
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fprintf(stderr, "Polygon clean failed\n");
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}
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}
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drawvec out;
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@ -438,20 +330,20 @@ drawvec reduce_tiny_poly(drawvec &geom, int z, int detail, bool *reduced, double
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area += geom[k].x * geom[i + ((k - i + 1) % (j - i))].y;
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area -= geom[k].y * geom[i + ((k - i + 1) % (j - i))].x;
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}
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area = fabs(area / 2);
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area = area / 2;
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if (area <= pixel * pixel) {
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if (fabs(area) <= pixel * pixel) {
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// printf("area is only %f vs %lld so using square\n", area, pixel * pixel);
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*accum_area += area;
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if (*accum_area > pixel * pixel) {
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// XXX use centroid;
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out.push_back(draw(VT_MOVETO, geom[i].x, geom[i].y));
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out.push_back(draw(VT_LINETO, geom[i].x + pixel, geom[i].y));
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out.push_back(draw(VT_LINETO, geom[i].x + pixel, geom[i].y + pixel));
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out.push_back(draw(VT_LINETO, geom[i].x, geom[i].y + pixel));
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out.push_back(draw(VT_LINETO, geom[i].x, geom[i].y));
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out.push_back(draw(VT_MOVETO, geom[i].x - pixel/2, geom[i].y - pixel/2));
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out.push_back(draw(VT_LINETO, geom[i].x + pixel/2, geom[i].y - pixel/2));
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out.push_back(draw(VT_LINETO, geom[i].x + pixel/2, geom[i].y + pixel/2));
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out.push_back(draw(VT_LINETO, geom[i].x - pixel/2, geom[i].y + pixel/2));
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out.push_back(draw(VT_LINETO, geom[i].x - pixel/2, geom[i].y - pixel/2));
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*accum_area -= pixel * pixel;
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}
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@ -20,7 +20,7 @@ drawvec decode_geometry(char **meta, int z, unsigned tx, unsigned ty, int detail
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void to_tile_scale(drawvec &geom, int z, int detail);
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drawvec remove_noop(drawvec geom, int type, int shift);
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drawvec clip_point(drawvec &geom, int z, int detail, long long buffer);
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drawvec clip_poly(drawvec &geom, int z, int detail, int buffer);
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drawvec clean_or_clip_poly(drawvec &geom, int z, int detail, int buffer, bool clip);
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drawvec reduce_tiny_poly(drawvec &geom, int z, int detail, bool *reduced, double *accum_area);
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drawvec clip_lines(drawvec &geom, int z, int detail, long long buffer);
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int quick_check(long long *bbox, int z, int detail, long long buffer);
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8
tile.cc
8
tile.cc
@ -580,7 +580,7 @@ long long write_tile(char **geoms, char *metabase, char *stringpool, unsigned *f
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geom = clip_lines(geom, z, line_detail, buffer);
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}
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if (t == VT_POLYGON) {
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geom = clip_poly(geom, z, line_detail, buffer);
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geom = clean_or_clip_poly(geom, z, line_detail, buffer, true);
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}
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if (t == VT_POINT) {
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geom = clip_point(geom, z, line_detail, buffer);
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@ -687,6 +687,12 @@ long long write_tile(char **geoms, char *metabase, char *stringpool, unsigned *f
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to_tile_scale(geom, z, line_detail);
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if (t == VT_POLYGON) {
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// Scaling may have made the polygon degenerate.
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// Give Clipper a chance to try to fix it.
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geom = clean_or_clip_poly(geom, 0, 0, 0, false);
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}
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if (t == VT_POINT || to_feature(geom, NULL)) {
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struct coalesce c;
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