Revision: 76195
http://sourceforge.net/p/brlcad/code/76195
Author: starseeker
Date: 2020-06-24 20:14:44 +0000 (Wed, 24 Jun 2020)
Log Message:
-----------
Demonstrate in principle snapping to the closest point to two line segments if
we are close to both of them. Need something much better than a hard coded
number for the tolerance, but the mechanism itself seems to function.
Modified Paths:
--------------
brlcad/trunk/src/libged/view/snap.c
Modified: brlcad/trunk/src/libged/view/snap.c
===================================================================
--- brlcad/trunk/src/libged/view/snap.c 2020-06-24 16:09:08 UTC (rev 76194)
+++ brlcad/trunk/src/libged/view/snap.c 2020-06-24 20:14:44 UTC (rev 76195)
@@ -41,48 +41,154 @@
return GED_ERROR;
}
+struct ged_cp_info {
+ double ctol_sq; // square of the distance that defines "close to a line"
+
+ struct bview_data_line_state *c_lset; // container holding closest line
+ point_t cp; // closest point on closest line
+ int c_l; // index of closest line
+ double dsq; // squared distance to closest line
+
+ struct bview_data_line_state *c_lset2; // container holding 2nd closest
line
+ point_t cp2; // closest point on closest line
+ int c_l2; // index of 2nd closest line
+ double dsq2; // squared distance to 2nd closest line
+};
+#define GED_CP_INFO_INIT {BN_TOL_DIST, NULL, VINIT_ZERO, -1, DBL_MAX, NULL,
VINIT_ZERO, -1, DBL_MAX}
+
+static
int
+_find_closest_point(struct ged_cp_info *s, point_t *p, struct
bview_data_line_state *lines)
+{
+ int ret = 0;
+ point_t P0, P1;
+
+ if (lines->gdls_num_points < 2) {
+ return ret;
+ }
+
+ // TODO - if we have a large number of lines drawn, we could really benefit
+ // from an acceleration structure such as the RTree to localize these tests
+ // rather than checking everything...
+ for (int i = 0; i < lines->gdls_num_points; i+=2) {
+ if (s->c_l == i && s->c_lset == lines) {
+ continue;
+ }
+ point_t c;
+ VMOVE(P0, lines->gdls_points[i]);
+ VMOVE(P1, lines->gdls_points[i+1]);
+ double dsq = bg_lseg_pt_dist_sq(&c, P0, P1, *p);
+ // If this is the closest we've seen, record it
+ if (s->dsq > dsq) {
+ // Closest is now second closest
+ VMOVE(s->cp2, s->cp);
+ s->dsq2 = s->dsq;
+ s->c_l2 = s->c_l;
+ s->c_lset2 = s->c_lset;
+
+ // set new closest
+ VMOVE(s->cp, c);
+ s->dsq = dsq;
+ s->c_l = i;
+ s->c_lset = lines;
+ printf("1st: %g: %g %g %g\n", sqrt(dsq), V3ARGS(c));
+ ret = 1;
+ continue;
+ }
+ // Not the closest - is it closer than the second closest?
+ if (s->dsq2 > dsq) {
+ VMOVE(s->cp2, c);
+ s->dsq2 = dsq;
+ s->c_l2 = i;
+ s->c_lset2 = lines;
+ printf("2nd: %g: %g %g %g\n", sqrt(dsq), V3ARGS(c));
+ ret = 2;
+ continue;
+ }
+ }
+
+ return ret;
+}
+
+void
+_find_close_isect(struct ged_cp_info *s, point_t *p)
+{
+ point_t P0, P1, Q0, Q1;
+ point_t c1, c2;
+
+ VMOVE(P0, s->c_lset->gdls_points[s->c_l]);
+ VMOVE(P1, s->c_lset->gdls_points[s->c_l+1]);
+
+ VMOVE(Q0, s->c_lset2->gdls_points[s->c_l2]);
+ VMOVE(Q1, s->c_lset2->gdls_points[s->c_l2+1]);
+
+ double csdist_sq = bg_lseg_lseg_dist_sq(&c1, &c2, P0, P1, Q0, Q1);
+ if (csdist_sq > s->ctol_sq) {
+ // Line segments are too far away to use both of them to override the
+ // original answer
+ return;
+ }
+
+ // If either closest segment point is too far from the test point, go with
+ // the original answer rather than changing it
+ double d1_sq = DIST_PNT_PNT_SQ(*p, c1);
+ if (d1_sq > s->ctol_sq) {
+ // Too far away to work
+ return;
+ }
+
+ double d2_sq = DIST_PNT_PNT_SQ(*p, c2);
+ if (d2_sq > s->ctol_sq) {
+ // Too far away to work
+ return;
+ }
+
+ // Go with the closest segment point to the original point. If
+ // the segments intersect the two points should be the same and
+ // it won't matter which is chosen, but if they don't then the
+ // intuitive behavior is to prefer the closest point that attempts
+ // to satisfy both line segments
+ if (d1_sq < d2_sq) {
+ VMOVE(s->cp, c1);
+ } else {
+ VMOVE(s->cp, c2);
+ }
+}
+
+int
ged_snap_lines_3d(struct ged *gedp, point_t *p)
{
- struct bview_data_line_state *lines = NULL;
+ struct ged_cp_info cpinfo = GED_CP_INFO_INIT;
+ cpinfo.ctol_sq = 100*100;
+
if (!p || !gedp) return GED_ERROR;
- bu_log("%g %g %g\n", V3ARGS(*p));
+
// There are some issues with line snapping that don't come up with grid
// snapping - in particular, when are we "close enough" to a line to snap,
// and how do we handle snapping when close enough to multiple lines? We
// probably want to prefer intersections between lines to closest line
// point if we are close to multiple lines...
+ int ret = 0;
+ ret += _find_closest_point(&cpinfo, p, &gedp->ged_gvp->gv_data_lines);
+ ret += _find_closest_point(&cpinfo, p, &gedp->ged_gvp->gv_sdata_lines);
- lines = &gedp->ged_gvp->gv_data_lines;
-
- if (lines->gdls_num_points > 1) {
- point_t P0, P1;
- for (int i = 0; i < lines->gdls_num_points; i+=2) {
- point_t c;
- VMOVE(P0, lines->gdls_points[i]);
- VMOVE(P1, lines->gdls_points[i+1]);
- double dsq = bg_lseg_pt_dist_sq(&c, P0, P1, *p);
- bu_log("%g: %g %g %g\n", sqrt(dsq), V3ARGS(c));
- }
+ // Check if we are close enough to two line segments to warrant using the
+ // closest approach point. The intersection may not be close enough to
+ // use, but if it is prefer it as it satisfies two lines instead of one.
+ if (ret > 1) {
+ _find_close_isect(&cpinfo, p);
}
- lines = &gedp->ged_gvp->gv_sdata_lines;
-
- if (lines->gdls_num_points > 1) {
- point_t P0, P1;
- for (int i = 0; i < lines->gdls_num_points; i+=2) {
- point_t c;
- VMOVE(P0, lines->gdls_points[i]);
- VMOVE(P1, lines->gdls_points[i+1]);
- double dsq = bg_lseg_pt_dist_sq(&c, P0, P1, *p);
- bu_log("%g: %g %g %g\n", sqrt(dsq), V3ARGS(c));
- }
+ // If we found something, we can snap
+ if (ret) {
+ bu_log("%g %g %g\n", V3ARGS(cpinfo.cp));
+ } else {
+ bu_log("no lines close enough for snapping\n");
}
-
- return GED_ERROR;
+ return GED_OK;
}
int
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