ignore intersections within eps of endpoints in %intersect/tan

Author: 3b

geometry.lisp

@@ -951,8 +951,13 @@
                (return-from %intersect/tan nil)))
          ;; scale so one curve is 0,0 1,0 1,1
          (m3 (scale (/ (vx a5)) (/ (vy a5))))
-         (a6 (mv* m3 a5))
-         (b6 (mv* m3 b5)))
+         #++(a6 (mv* m3 a5))
+         (b6 (mv* m3 b5))
+         (eps (* 16 (* double-float-epsilon
+                       (max (abs (vx p1)) (abs (vy p1))
+                            (abs (vx pc)) (abs (vy pc))
+                            (abs (vx a2)) (abs (vy a2))
+                            (abs (vx b2)) (abs (vy b2)))))))
     (declare (ignore r1 r2))
     ;; x₁ = 2t₁-t₁²
     ;; y₁ = t₁²
@@ -1029,16 +1034,19 @@
              (b (vy b6))
              (t2 (/ (* 2 (- (sqrt b) 1))
                     (+ a b -2)))
-             (t1 (* t2 (sqrt b))))
-        (flet ((e (p2 at)
-                 (let ((d1 (v2- pc p1))
-                       (d2 (v2+ p1 (v2+ (v2scale pc -2) p2))))
-                   (v2+ (v2+ (v2scale d2 (* at at))
-                             (v2scale d1 (* 2 at)))
-                        p1))))
-          (if (eql ref :a)
-              (v2->4 (e b2 t2) t1 t2)
-              (v2->4 (e a2 t2) t2 t1)))))))
+             (t1 (* t2 (sqrt b)))
+             (1-eps (- 1 eps)))
+        (when (and (< eps t1 1-eps)
+                   (< eps t2 1-eps))
+          (flet ((e (p2 at)
+                   (let ((d1 (v2- pc p1))
+                         (d2 (v2+ p1 (v2+ (v2scale pc -2) p2))))
+                     (v2+ (v2+ (v2scale d2 (* at at))
+                               (v2scale d1 (* 2 at)))
+                          p1))))
+            (if (eql ref :a)
+                (v2->4 (e b2 t2) t1 t2)
+                (v2->4 (e a2 t2) t2 t1))))))))
 
 
 

intersect-regression.lisp

@@ -691,6 +691,20 @@
   (ix2r (1578 1403 1664 1415 1689 1409) 1 0.6666666666666666d0
         (1689 1409 1663 1415 1578 1403) 1 0.3333333333333333d0
         NIL)
+  (ix2 (366 210 367 212 368 213)
+       (366.5d0 210.5d0 367 212 368 213)
+       #(368.0d0 213.0d0 1.0d0 1.0d0))
+  (ix2r (940 -21 940 -19 901 -32) 0 0.13333333333333333d0
+        (866 20 940 -19 940 -21) 1 0
+        #(940.0d0 -21.0d0 0.0d0 1.0d0)
+        #(939.9606309949041d0 -20.888053818960884d0
+          0.031772026518992295d0 0.9769345803771983d0))
+
+  (ix2 (940 -21 940 -19 901 -32)
+       (866 20 940 -19 940 -21)
+       #(940.0d0 -21.0d0 0.0d0 1.0d0)
+       #(939.9606309949041d0 -20.888053818960884d0
+         0.031772026518992295d0 0.9769345803771983d0))
 
   )
 #++