Zooming in Arcball?

pen51

Hello,

 

Does anyone have any advice about zooming in on the arcball while already in the scene? I don't want to just change the perspective, I want the user to be able to zoom in and out of the current scene.

 

Thanks!

Craige_Hales

You can follow this pattern for both scale and translate. The arcball holds some state information, so you don't want to destroy it and recreate it. I made two sliders, one outside of the arcball and one inside. The outer one scales the arcball, the inner just the arcball's content. (Modified from the HelloWorld sample script.)

// Show some text in an ArcBall

Names Default To Here( 1 );

// this tiny list is rebuilt when the inside slider moves
scaleinside=1;
scaleinsideList = scenedisplaylist();
scaleinsideList<<scale(scaleinside,scaleinside,scaleinside);

greeting = Scene Display List();
// place the call to the inside list inside the arcball
greeting<<calllist(scaleinsideList);
greeting << color( .9, .9, .9 ); // .1,.1,.1 = almost black    .9,.9,.9 = almost white
greeting << Text( center, middle, .3, "Hello 3D World" );

// this tiny list is rebuilt when the outside slider moves
scaleoutside=1;
scaleoutsideList = scenedisplaylist();
scaleoutsideList<<scale(scaleoutside,scaleoutside,scaleoutside);

// this is the main list, built one time
Scene = Scene Box( 600, 600 );
Scene << backgroundcolor( 0 ); // black=0, gray=1, white=2
Scene << showarcball( always );
Scene << perspective( 45, .2, 20 );
Scene << Translate( 0.0, 0.0, -4.5 );
//by placing this call before the arcball, it scales the arcball too
scene<<calllist(scaleoutsideList);
Scene << arcball( greeting, 1.5 );
Scene << update;

// the window contains a 3D display and two sliders
New Window( "x", 
    Scene//
    ,//
    sliderbox(.5,2,scaleinside,
        scaleinsideList<<clear;
        scaleinsideList<<scale(scaleinside,scaleinside,scaleinside);
        Scene << update;
    )//
    ,//
    sliderbox(.5,2,scaleoutside,
        scaleoutsideList<<clear;
        scaleoutsideList<<scale(scaleoutside,scaleoutside,scaleoutside);
        Scene << update;
    ) ;
);

The script is organized so only the least part of the script needs to be rebuilt by the slider callbacks.