From 32e8e922da6f5a20ff88934672c1ce1177b912de Mon Sep 17 00:00:00 2001
From: "W. Trevor King" <wking@drexel.edu>
Date: Wed, 12 Aug 2009 04:58:09 -0400
Subject: [PATCH] Added out-of-plane vectors to Mechanics.asy.

And associated tests to Mechanics-test.asy.
---
 asymptote/Mechanics-test.asy |  4 +++
 asymptote/Mechanics.asy      | 47 ++++++++++++++++++++++++++++--------
 2 files changed, 41 insertions(+), 10 deletions(-)

diff --git a/asymptote/Mechanics-test.asy b/asymptote/Mechanics-test.asy
index e3843e1..acbc701 100644
--- a/asymptote/Mechanics-test.asy
+++ b/asymptote/Mechanics-test.asy
@@ -36,6 +36,10 @@ Vector vs[];
 vs.push(ihat(center=(0,u)));
 vs.push(jhat(center=(0,u)));
 
+vs.push(Vector(center=(-1u,-4u), phi=90, "Out"));
+vs.push(Vector(center=(-1u,-5.5u), phi=-90, "In"));
+vs.push(Vector(center=(0, -4u), mag=1.5u, dir=-90, phi=60, "60dg OOP"));
+
 for (int i=0; i<ms.length; i+=1)
   ms[i].draw();
 for (int i=0; i<ds.length; i+=1)
diff --git a/asymptote/Mechanics.asy b/asymptote/Mechanics.asy
index 477e91c..ab353a0 100644
--- a/asymptote/Mechanics.asy
+++ b/asymptote/Mechanics.asy
@@ -85,16 +85,22 @@ struct Block {
 struct Vector {
   pair center;
   real mag;
-  real dir;
+  real dir; // angle in the plane of the drawing.
+  real phi; // angle with the plane of the drawing, 90 is out of the page.
   pen outline;
   Label L;
-  
-  void operator init(pair center=(0,0), real mag=5mm, real dir=0, pen outline=currentpen, Label L="") {
+  real out_of_plane_radius;
+  real out_of_plane_tolerance;
+
+  void operator init(pair center=(0,0), real mag=5mm, real dir=0, real phi=0, pen outline=currentpen, Label L="") {
     this.center = center;
     this.mag = mag;
     this.dir = dir;
+    this.phi = phi;
     this.outline = outline;
     this.L = L;
+    this.out_of_plane_radius = 3mm;
+    this.out_of_plane_tolerance = 0.01;
   }
 
   pair pTip() {
@@ -103,16 +109,37 @@ struct Vector {
   
   void draw(picture pic=currentpicture, bool rotateLabel=false, pair labelOffset=(0,0)) {
     picture picF;
-    pair p = this.mag*dir(this.dir);
-    path P = (0,0)--p;
-    pair label_rotate = p;
-    draw(picF, P, outline, Arrow);
-    if (rotateLabel == false)
-      label_rotate = (1,0);
+    pair p = (0,0);
+    pair label_rotate = (1,0);
+    pair label_align = (0,1);
+    real phi_e = this.phi % 360; // effective phi
+    if (this.mag < 0) (phi_e + 180) % 360;
+    if (Tan(phi_e) == 0 || abs(1.0/Tan(phi_e)) > this.out_of_plane_tolerance) {
+      // draw arrow in the plane of the drawing
+      // TODO: thickening for phi?
+      p = this.mag*Cos(this.phi)*dir(this.dir);
+      path P = (0,0)--p;
+      draw(picF, P, outline, Arrow);
+      if (rotateLabel == true)
+	label_rotate = p;
+      label_align = unit(rotate(90)*p);
+    } else if (phi_e > 0 && phi_e < 180) {
+      // draw a circled dot for out-of-the-page
+      p = (0, this.out_of_plane_radius);
+      draw(picF, scale(this.out_of_plane_radius)*unitcircle, outline);
+      dot(picF, (0,0), outline);
+    } else {
+      // draw a circled cross for into-the-page
+      real a = 0.8*sqrt(2.0)/2.0;
+      p = (0, this.out_of_plane_radius);
+      draw(picF, scale(this.out_of_plane_radius)*unitcircle, outline);
+      draw(picF, scale(this.out_of_plane_radius)*((-a,-a)--(a,a)), outline);
+      draw(picF, scale(this.out_of_plane_radius)*((-a,a)--(a,-a)), outline);
+    }
     label(pic = picF,
 	  L = rotate(degrees(label_rotate)) * L,
 	  position = p+labelOffset,
-	  align = unit(rotate(90)*p));
+	  align = label_align);
     add(pic, picF, center);
   }
 }
-- 
2.26.2