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Clip in floating point, not integers, which makes no difference

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This commit is contained in:
Erica Fischer
2023-09-07 16:26:42 -07:00
parent 30526cac3c
commit fde8e944aa
1 changed files with 26 additions and 28 deletions
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geometry.cpp
+26 -28
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@@ -557,41 +557,38 @@ drawvec close_poly(drawvec &geom) {
// @@@
// @@@
static bool inside(draw d, int edge, long long minx, long long miny, long long maxx, long long maxy) {
static bool inside(std::pair<double, double> d, int edge, long long minx, long long miny, long long maxx, long long maxy) {
switch (edge) {
case 0: // top
return d.y > miny;
return d.second > miny;
case 1: // right
return d.x < maxx;
return d.first < maxx;
case 2: // bottom
return d.y < maxy;
return d.second < maxy;
case 3: // left
return d.x > minx;
return d.first > minx;
}
fprintf(stderr, "internal error inside\n");
exit(EXIT_FAILURE);
}
static draw intersect(draw a, draw b, int edge, long long minx, long long miny, long long maxx, long long maxy) {
// The casts to double are because the product of coordinates
// can overflow a long long if the tile buffer is large.
static std::pair<double, double> intersect(std::pair<double, double> a, std::pair<double, double> b, int edge, long long minx, long long miny, long long maxx, long long maxy) {
switch (edge) {
case 0: // top
return draw(VT_LINETO, std::round(a.x + (double) (b.x - a.x) * (miny - a.y) / (b.y - a.y)), miny);
return std::pair<double, double>((a.first + (double) (b.first - a.first) * (miny - a.second) / (b.second - a.second)), miny);
case 1: // right
return draw(VT_LINETO, maxx, std::round(a.y + (double) (b.y - a.y) * (maxx - a.x) / (b.x - a.x)));
return std::pair<double, double>(maxx, (a.second + (double) (b.second - a.second) * (maxx - a.first) / (b.first - a.first)));
case 2: // bottom
return draw(VT_LINETO, std::round(a.x + (double) (b.x - a.x) * (maxy - a.y) / (b.y - a.y)), maxy);
return std::pair<double, double>((a.first + (double) (b.first - a.first) * (maxy - a.second) / (b.second - a.second)), maxy);
case 3: // left
return draw(VT_LINETO, minx, std::round(a.y + (double) (b.y - a.y) * (minx - a.x) / (b.x - a.x)));
return std::pair<double, double>(minx, (a.second + (double) (b.second - a.second) * (minx - a.first) / (b.first - a.first)));
}
fprintf(stderr, "internal error intersecting\n");
@@ -599,18 +596,18 @@ static draw intersect(draw a, draw b, int edge, long long minx, long long miny,
}
// http://en.wikipedia.org/wiki/Sutherland%E2%80%93Hodgman_algorithm
static drawvec clip_poly1(drawvec &geom, long long minx, long long miny, long long maxx, long long maxy) {
drawvec out = geom;
static std::vector<std::pair<double, double>> clip_poly1(std::vector<std::pair<double, double>> &geom, long long minx, long long miny, long long maxx, long long maxy) {
std::vector<std::pair<double, double>> out = geom;
for (int edge = 0; edge < 4; edge++) {
if (out.size() > 0) {
drawvec in = out;
std::vector<std::pair<double, double>> in = out;
out.resize(0);
draw S = in[in.size() - 1];
std::pair<double, double> S = in[in.size() - 1];
for (size_t e = 0; e < in.size(); e++) {
draw E = in[e];
std::pair<double, double> E = in[e];
if (inside(E, edge, minx, miny, maxx, maxy)) {
if (!inside(S, edge, minx, miny, maxx, maxy)) {
@@ -632,7 +629,7 @@ static drawvec clip_poly1(drawvec &geom, long long minx, long long miny, long lo
// places where it intersects the edge. Need to add
// another point to close the loop.
if (out[0].x != out[out.size() - 1].x || out[0].y != out[out.size() - 1].y) {
if (out[0].first != out[out.size() - 1].first || out[0].second != out[out.size() - 1].second) {
out.push_back(out[0]);
}
@@ -641,11 +638,6 @@ static drawvec clip_poly1(drawvec &geom, long long minx, long long miny, long lo
out.clear();
return out;
}
out[0].op = VT_MOVETO;
for (size_t i = 1; i < out.size(); i++) {
out[i].op = VT_LINETO;
}
}
return out;
@@ -663,19 +655,25 @@ drawvec simple_clip_poly(drawvec &geom, long long minx, long long miny, long lon
}
}
drawvec tmp;
std::vector<std::pair<double, double>> tmp;
for (size_t k = i; k < j; k++) {
tmp.push_back(geom[k]);
double x = geom[k].x;
double y = geom[k].y;
tmp.emplace_back(x, y);
}
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) {
if (tmp[0].first != tmp[tmp.size() - 1].first || tmp[0].second != tmp[tmp.size() - 1].second) {
fprintf(stderr, "Internal error: Polygon ring not closed\n");
exit(EXIT_FAILURE);
}
}
for (size_t k = 0; k < tmp.size(); k++) {
out.push_back(tmp[k]);
if (k == 0) {
out.push_back(draw(VT_MOVETO, std::round(tmp[k].first), std::round(tmp[k].second)));
} else {
out.push_back(draw(VT_LINETO, std::round(tmp[k].first), std::round(tmp[k].second)));
}
}
i = j - 1;