Add two more exotic constraints: equal point-line distances, and

point-line distance equal to line segment length. These are
available in both normal and projected versions, with fancy display
for all of these.

[git-p4: depot-paths = "//depot/solvespace/": change = 1793]

constraint.cpp

@@ -16,6 +16,8 @@ char *Constraint::DescriptionString(void) {
         case PT_ON_LINE:        s = "pt-on-line"; break;
         case PT_ON_FACE:        s = "pt-on-face"; break;
         case EQUAL_LENGTH_LINES:s = "eq-length"; break;
+        case EQ_LEN_PT_LINE_D:  s = "eq-length-and-pt-ln-dist"; break;
+        case EQ_PT_LN_DISTANCES:s = "eq-pt-line-distances"; break;
         case LENGTH_RATIO:      s = "length-ratio"; break;
         case SYMMETRIC:         s = "symmetric"; break;
         case SYMMETRIC_HORIZ:   s = "symmetric-h"; break;
@@ -154,6 +156,25 @@ void Constraint::MenuConstrain(int id) {
                 c.type = EQUAL_LENGTH_LINES;
                 c.entityA = gs.entity[0];
                 c.entityB = gs.entity[1];
+            } else if(gs.lineSegments == 2 && gs.points == 2 && gs.n == 4) {
+                c.type = EQ_PT_LN_DISTANCES;
+                c.entityA = gs.entity[0];
+                c.ptA = gs.point[0];
+                c.entityB = gs.entity[1];
+                c.ptB = gs.point[1];
+            } else if(gs.lineSegments == 1 && gs.points == 2 && gs.n == 3) {
+                // The same line segment for the distances, but different
+                // points.
+                c.type = EQ_PT_LN_DISTANCES;
+                c.entityA = gs.entity[0];
+                c.ptA = gs.point[0];
+                c.entityB = gs.entity[0];
+                c.ptB = gs.point[1];
+            } else if(gs.lineSegments == 2 && gs.points == 1 && gs.n == 3) {
+                c.type = EQ_LEN_PT_LINE_D;
+                c.entityA = gs.entity[0];
+                c.entityB = gs.entity[1];
+                c.ptA = gs.point[0];
             } else if(gs.circlesOrArcs == 2 && gs.n == 2) {
                 c.type = EQUAL_RADIUS;
                 c.entityA = gs.entity[0];
@@ -552,6 +573,22 @@ void Constraint::GenerateReal(IdList<Equation,hEquation> *l) {
             break;
         }
 
+        // These work on distance squared, since the pt-line distances are
+        // signed, and we want the absolute value.
+        case EQ_LEN_PT_LINE_D: {
+            Entity *forLen = SS.GetEntity(entityA);
+            Expr *d1 = Distance(workplane, forLen->point[0], forLen->point[1]);
+            Expr *d2 = PointLineDistance(workplane, ptA, entityB);
+            AddEq(l, (d1->Square())->Minus(d2->Square()), 0);
+            break;
+        }
+        case EQ_PT_LN_DISTANCES: {
+            Expr *d1 = PointLineDistance(workplane, ptA, entityA);
+            Expr *d2 = PointLineDistance(workplane, ptB, entityB);
+            AddEq(l, (d1->Square())->Minus(d2->Square()), 0);
+            break;
+        }
+
         case LENGTH_RATIO: {
             Entity *a = SS.GetEntity(entityA);
             Entity *b = SS.GetEntity(entityB);

drawconstraint.cpp

@@ -95,6 +95,14 @@ void Constraint::DoProjectedPoint(Vector *r) {
     *r = p;
 }
 
+void Constraint::DoEqualLenTicks(Vector a, Vector b, Vector gn) {
+    Vector m = (a.ScaledBy(1.0/3)).Plus(b.ScaledBy(2.0/3));
+    Vector ab = a.Minus(b);
+    Vector n = (gn.Cross(ab)).WithMagnitude(10/SS.GW.scale);
+    
+    LineDrawOrGetDistance(m.Minus(n), m.Plus(n));
+}
+
 void Constraint::DrawOrGetDistance(Vector *labelPos) {
     if(!SS.GW.showConstraints) return;
     Group *g = SS.GetGroup(group);
@@ -172,18 +180,8 @@ void Constraint::DrawOrGetDistance(Vector *labelPos) {
                 DoProjectedPoint(&pt);
             }
 
-            Vector lAB = (lA.Minus(lB)).WithMagnitude(1);
+            // Find the closest point on the line
-            Vector closest;
+            Vector closest = pt.ClosestPointOnLine(lA, (lA.Minus(lB)));
-            // lA, lB, and pt define a plane; the min distance is in
-            // that plane, so calculate its normal
-            Vector pn = (pt.Minus(lA)).Cross(lAB);
-            // The minimum distance line is in that plane, perpendicular
-            // to the line
-            Vector n = pn.Cross(lAB);
-
-            // Calculate the actual distance
-            double d = (lAB.Cross(lA.Minus(pt))).Magnitude();
-            closest = pt.Plus(n.WithMagnitude(d));
 
             LineDrawOrGetDistance(pt, closest);
             Vector ref = ((closest.Plus(pt)).ScaledBy(0.5)).Plus(disp.offset);
@@ -192,7 +190,7 @@ void Constraint::DrawOrGetDistance(Vector *labelPos) {
             if(workplane.v != Entity::FREE_IN_3D.v) {
                 // Draw the projection marker from the closest point on the
                 // projected line to the projected point on the real line.
-                lAB = (lA.Minus(lB));
+                Vector lAB = (lA.Minus(lB));
                 double t = (lA.Minus(closest)).DivPivoting(lAB);
 
                 Vector lA = SS.GetEntity(line->point[0])->PointGetNum();
@@ -422,11 +420,13 @@ void Constraint::DrawOrGetDistance(Vector *labelPos) {
                 Entity *e = SS.GetEntity(i == 0 ? entityA : entityB);
                 a = SS.GetEntity(e->point[0])->PointGetNum();
                 b = SS.GetEntity(e->point[1])->PointGetNum();
-                Vector m = (a.ScaledBy(1.0/3)).Plus(b.ScaledBy(2.0/3));
-                Vector ab = a.Minus(b);
-                Vector n = (gn.Cross(ab)).WithMagnitude(10/SS.GW.scale);
 
-                LineDrawOrGetDistance(m.Minus(n), m.Plus(n));
+                if(workplane.v != Entity::FREE_IN_3D.v) {
+                    DoProjectedPoint(&a);
+                    DoProjectedPoint(&b);
+                }
+
+                DoEqualLenTicks(a, b, gn);
             }
             if(type == LENGTH_RATIO) {
                 Vector ref = ((a.Plus(b)).ScaledBy(0.5)).Plus(disp.offset);
@@ -435,6 +435,54 @@ void Constraint::DrawOrGetDistance(Vector *labelPos) {
             break;
         }
 
+        case EQ_LEN_PT_LINE_D: {
+            Entity *forLen = SS.GetEntity(entityA);
+            Vector a = SS.GetEntity(forLen->point[0])->PointGetNum(),
+                   b = SS.GetEntity(forLen->point[1])->PointGetNum();
+            if(workplane.v != Entity::FREE_IN_3D.v) {
+                DoProjectedPoint(&a);
+                DoProjectedPoint(&b);
+            }
+            DoEqualLenTicks(a, b, gn);
+
+            Entity *ln = SS.GetEntity(entityB);
+            Vector la = SS.GetEntity(ln->point[0])->PointGetNum(),
+                   lb = SS.GetEntity(ln->point[1])->PointGetNum();
+            Vector pt = SS.GetEntity(ptA)->PointGetNum();
+            if(workplane.v != Entity::FREE_IN_3D.v) {
+                DoProjectedPoint(&pt);
+                la = la.ProjectInto(workplane);
+                lb = lb.ProjectInto(workplane);
+            }
+
+            Vector closest = pt.ClosestPointOnLine(la, lb.Minus(la));
+            LineDrawOrGetDistance(pt, closest);
+            DoEqualLenTicks(pt, closest, gn);
+            break;
+        }
+
+        case EQ_PT_LN_DISTANCES: {
+            for(int i = 0; i < 2; i++) {
+                Entity *ln = SS.GetEntity(i == 0 ? entityA : entityB);
+                Vector la = SS.GetEntity(ln->point[0])->PointGetNum(),
+                       lb = SS.GetEntity(ln->point[1])->PointGetNum();
+                Entity *pte = SS.GetEntity(i == 0 ? ptA : ptB);
+                Vector pt = pte->PointGetNum();
+
+                if(workplane.v != Entity::FREE_IN_3D.v) {
+                    DoProjectedPoint(&pt);
+                    la = la.ProjectInto(workplane);
+                    lb = lb.ProjectInto(workplane);
+                }
+
+                Vector closest = pt.ClosestPointOnLine(la, lb.Minus(la));
+
+                LineDrawOrGetDistance(pt, closest);
+                DoEqualLenTicks(pt, closest, gn);
+            }
+            break;
+        }
+
         {
         Vector n; 
         case SYMMETRIC:

dsc.h

@@ -56,6 +56,7 @@ public:
     Vector RotatedAbout(Vector orig, Vector axis, double theta);
     Vector RotatedAbout(Vector axis, double theta);
     double DistanceToLine(Vector p0, Vector dp);
+    Vector ClosestPointOnLine(Vector p0, Vector dp);
     double Magnitude(void);
     Vector WithMagnitude(double s);
     Vector ScaledBy(double s);

sketch.h

@@ -412,6 +412,8 @@ public:
     static const int PT_ON_FACE         =  43;
     static const int EQUAL_LENGTH_LINES =  50;
     static const int LENGTH_RATIO       =  51;
+    static const int EQ_LEN_PT_LINE_D   =  52;
+    static const int EQ_PT_LN_DISTANCES =  53;
     static const int SYMMETRIC          =  60;
     static const int SYMMETRIC_HORIZ    =  61;
     static const int SYMMETRIC_VERT     =  62;
@@ -471,6 +473,7 @@ public:
     char *Label(void);
     void DoLabel(Vector ref, Vector *labelPos, Vector gr, Vector gu);
     void DoProjectedPoint(Vector *p);
+    void DoEqualLenTicks(Vector a, Vector b, Vector gn);
 
     double GetDistance(Point2d mp);
     Vector GetLabelPos(void);

util.cpp

@@ -315,6 +315,20 @@ double Vector::DistanceToLine(Vector p0, Vector dp) {
     return ((this->Minus(p0)).Cross(dp)).Magnitude() / m;
 }
 
+Vector Vector::ClosestPointOnLine(Vector p0, Vector dp) {
+    dp = dp.WithMagnitude(1);
+    // this, p0, and (p0+dp) define a plane; the min distance is in
+    // that plane, so calculate its normal
+    Vector pn = (this->Minus(p0)).Cross(dp);
+    // The minimum distance line is in that plane, perpendicular
+    // to the line
+    Vector n = pn.Cross(dp);
+
+    // Calculate the actual distance
+    double d = (dp.Cross(p0.Minus(*this))).Magnitude();
+    return this->Plus(n.WithMagnitude(d));
+}
+
 double Vector::Magnitude(void) {
     return sqrt(x*x + y*y + z*z);
 }