Hi all, I've been thinking about 3d rotation using the mouse - normally I've mapped the mouse x/y coordinates to rotation values.  However, this means that when you click on the screen the model jumps to that rotation.

Instead, I wanted to click-and-drag to incrementally rotate, more like in a 3d modeling program.  Here's my working version:

1. int boxSize = 600;                             // size for 3d box
   
2. float inc = 0.05;                                 // increment to rotate during drag
   
3. color orange = color(212, 124, 23);   // fill color
   
4. float rx, ry;                                         // keep track of rotation x/y
   
5. 
   
6. void setup() {
   
7.   size(500,500, OPENGL);
   
8.   strokeWeight(20);
   
9.  
   
10.   // initial rotation
    
11.   rx = radians(-25);
    
12.   ry = radians(45);
    
13. }
    
14. 
    
15. void draw() {
    
16.   background(0);
    
17.  
    
18.   // rotate from center
    
19.   translate(width/2, height/2, -boxSize*5);
    
20.   rotateX(rx);
    
21.   rotateY(ry);
    
22.  
    
23.   // box!
    
24.   stroke(0);
    
25.   fill(orange);
    
26.   box(boxSize);
    
27.  
    
28.   // directional lines
    
29.   pushMatrix();
    
30.   translate(-boxSize*2, boxSize/2, boxSize/2);
    
31.   stroke(255,0,0);
    
32.   line(0,0,0, boxSize, 0, 0);
    
33.   stroke(0,255,0);
    
34.   line(0,0,0, 0, -boxSize,0);
    
35.   stroke(0,0,255);
    
36.   line(0,0,0, 0,0,-boxSize);
    
37.   popMatrix();
    
38. }
    
39. 
    
40. // the magic happens here!
    
41. void mouseDragged() {
    
42.  
    
43.   // normally we'd do something like this
    
44.   // ry = map(mouseX, 0,width, 0,TWO_PI);
    
45.   // rx = map(mouseY, 0,height, 0,TWO_PI);
    
46.  
    
47.   // drag in x direction, rotate y
    
48.   if (mouseX > pmouseX) {
    
49.     ry += inc;
    
50.   }
    
51.   else if (mouseX < pmouseX) {
    
52.     ry -= inc;
    
53.   }
    
54.  
    
55.   // ditto y
    
56.   if (mouseY > pmouseY) {
    
57.     rx -= inc;
    
58.   }
    
59.   else if (mouseY < pmouseY) {
    
60.     rx += inc;
    
61.   }
    
62. }

This seems to work ok, but I'm looking for suggestions to make this more natural.  Ideas?