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Refactor simple polygon clipping for arbitrary bounding boxes

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This commit is contained in:
Eric Fischer 2016-02-11 11:31:53 -08:00
parent c6ad34427a
commit ef646e8414
1 changed files with 76 additions and 31 deletions
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107
geometry.cc
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@ -341,21 +341,19 @@ drawvec close_poly(drawvec &geom) {
return out;
}
static bool inside(draw d, int edge, long long area, long long buffer) {
long long clip_buffer = buffer * area / 256;
static bool inside(draw d, int edge, long long minx, long long miny, long long maxx, long long maxy) {
switch (edge) {
case 0: // top
return d.y > -clip_buffer;
return d.y > miny;
case 1: // right
return d.x < area + clip_buffer;
return d.x < maxx;
case 2: // bottom
return d.y < area + clip_buffer;
return d.y < maxy;
case 3: // left
return d.x > -clip_buffer;
return d.x > minx;
}
fprintf(stderr, "internal error inside\n");
@ -376,24 +374,22 @@ static draw get_line_intersection(draw p0, draw p1, draw p2, draw p3) {
return draw(VT_LINETO, p0.x + (t * s1_x), p0.y + (t * s1_y));
}
static draw intersect(draw a, draw b, int edge, long long area, long long buffer) {
long long clip_buffer = buffer * area / 256;
static draw intersect(draw a, draw b, int edge, long long minx, long long miny, long long maxx, long long maxy) {
switch (edge) {
case 0: // top
return get_line_intersection(a, b, draw(VT_MOVETO, -clip_buffer, -clip_buffer), draw(VT_MOVETO, area + clip_buffer, -clip_buffer));
return get_line_intersection(a, b, draw(VT_MOVETO, minx, miny), draw(VT_MOVETO, maxx, miny));
break;
case 1: // right
return get_line_intersection(a, b, draw(VT_MOVETO, area + clip_buffer, -clip_buffer), draw(VT_MOVETO, area + clip_buffer, area + clip_buffer));
return get_line_intersection(a, b, draw(VT_MOVETO, maxx, miny), draw(VT_MOVETO, maxx, maxy));
break;
case 2: // bottom
return get_line_intersection(a, b, draw(VT_MOVETO, area + clip_buffer, area + clip_buffer), draw(VT_MOVETO, -clip_buffer, area + clip_buffer));
return get_line_intersection(a, b, draw(VT_MOVETO, maxx, maxy), draw(VT_MOVETO, minx, maxy));
break;
case 3: // left
return get_line_intersection(a, b, draw(VT_MOVETO, -clip_buffer, area + clip_buffer), draw(VT_MOVETO, -clip_buffer, -clip_buffer));
return get_line_intersection(a, b, draw(VT_MOVETO, minx, maxy), draw(VT_MOVETO, minx, miny));
break;
}
@ -402,14 +398,9 @@ static draw intersect(draw a, draw b, int edge, long long area, long long buffer
}
// http://en.wikipedia.org/wiki/Sutherland%E2%80%93Hodgman_algorithm
static drawvec clip_poly1(drawvec &geom, int z, int detail, int buffer) {
static drawvec clip_poly1(drawvec &geom, long long minx, long long miny, long long maxx, long long maxy) {
drawvec out = geom;
long long area = 0xFFFFFFFF;
if (z != 0) {
area = 1LL << (32 - z);
}
for (int edge = 0; edge < 4; edge++) {
if (out.size() > 0) {
drawvec in = out;
@ -420,13 +411,13 @@ static drawvec clip_poly1(drawvec &geom, int z, int detail, int buffer) {
for (unsigned e = 0; e < in.size(); e++) {
draw E = in[e];
if (inside(E, edge, area, buffer)) {
if (!inside(S, edge, area, buffer)) {
out.push_back(intersect(S, E, edge, area, buffer));
if (inside(E, edge, minx, miny, maxx, maxy)) {
if (!inside(S, edge, minx, miny, maxx, maxy)) {
out.push_back(intersect(S, E, edge, minx, miny, maxx, maxy));
}
out.push_back(E);
} else if (inside(S, edge, area, buffer)) {
out.push_back(intersect(S, E, edge, area, buffer));
} else if (inside(S, edge, minx, miny, maxx, maxy)) {
out.push_back(intersect(S, E, edge, minx, miny, maxx, maxy));
}
S = E;
@ -457,11 +448,7 @@ static drawvec clip_poly1(drawvec &geom, int z, int detail, int buffer) {
return out;
}
drawvec simple_clip_poly(drawvec &geom, int z, int detail, int buffer) {
if (z == 0) {
return geom;
}
drawvec simple_clip_poly(drawvec &geom, long long minx, long long miny, long long maxx, long long maxy) {
drawvec out;
for (unsigned i = 0; i < geom.size(); i++) {
@ -477,7 +464,7 @@ drawvec simple_clip_poly(drawvec &geom, int z, int detail, int buffer) {
for (unsigned k = i; k < j; k++) {
tmp.push_back(geom[k]);
}
tmp = clip_poly1(tmp, z, detail, buffer);
tmp = clip_poly1(tmp, minx, miny, maxx, maxy);
if (tmp.size() > 0) {
if (tmp[0].x != tmp[tmp.size() - 1].x || tmp[0].y != tmp[tmp.size() - 1].y) {
fprintf(stderr, "Internal error: Polygon ring not closed\n");
@ -498,6 +485,17 @@ drawvec simple_clip_poly(drawvec &geom, int z, int detail, int buffer) {
return out;
}
drawvec simple_clip_poly(drawvec &geom, int z, int detail, int buffer) {
long long area = 0xFFFFFFFF;
if (z != 0) {
area = 1LL << (32 - z);
}
long long clip_buffer = buffer * area / 256;
return simple_clip_poly(geom, -clip_buffer, -clip_buffer, area + clip_buffer, area + clip_buffer);
}
drawvec reduce_tiny_poly(drawvec &geom, int z, int detail, bool *reduced, double *accum_area) {
drawvec out;
long long pixel = (1 << (32 - detail - z)) * 2;
@ -943,3 +941,50 @@ drawvec fix_polygon(drawvec &geom) {
return out;
}
std::vector<drawvec> chop_polygon(std::vector<drawvec> &geoms) {
return geoms;
while (1) {
bool again = false;
std::vector<drawvec> out;
for (unsigned i = 0; i < geoms.size(); i++) {
if (geoms[i].size() > 700) {
again = true;
long long midx = 0, midy = 0, count = 0;
long long maxx = LONG_LONG_MIN, maxy = LONG_LONG_MIN, minx = LONG_LONG_MAX, miny = LONG_LONG_MAX;
for (unsigned j = 0; j < geoms[i].size(); j++) {
if (geoms[i][j].op == VT_MOVETO || geoms[i][j].op == VT_LINETO) {
midx += geoms[i][j].x;
midy += geoms[i][j].y;
count++;
if (geoms[i][j].x > maxx) {
maxx = geoms[i][j].x;
}
if (geoms[i][j].y > maxy) {
maxy = geoms[i][j].y;
}
if (geoms[i][j].x < minx) {
minx = geoms[i][j].x;
}
if (geoms[i][j].y < miny) {
miny = geoms[i][j].y;
}
}
}
} else {
out.push_back(geoms[i]);
}
}
if (!again) {
return out;
}
geoms = out;
}
}