Pivot for rotation of Mesh

[kapilreddy]

A pivot for rotation for a objects would useful. Right now I am doing that using a locus equation but in built feature would be useful

[mrdoob]

Depending of what you're after you could just offset all the vertices instead. But I agree, having a pivot could be useful. I haven't had a chance to implement yet (there have been some branches that implemented that, plus hierarchy, but haven't had a chance to properly merge them and test it yet).

[kapilreddy]

Yes hierarchy is also a good addition. Could you please point me to the brances that actually implement pivot and hierarchy

[525c1e21-bd67-4735-ac99-b4b0e5262290]

Why has this been closed? Hierarchy will be an essential feature moving forwards although I cannot find any trace of support yet...correct me if I am wrong.

I'll open an issue for Hierarchy

[mrdoob]

A workaround was suggested. I think it was via twitter :S

[525c1e21-bd67-4735-ac99-b4b0e5262290]

I had a quick search but couldn't find anything relevant. Do you remember what was suggested?

[mrdoob]

Basically, offset the vertices instead. If you want the pivot to be at 100,0,0... offset all the vertices -100,0,0. Not an ideal solution but is a good workaround and saves a bunch of computations.

[kapilreddy]

Hey i am back on it after a while but seems like offseting vertices is not a good idea if you want alot of objects rotating on a same pivot.

[mrdoob]

Have you tried grouping them? Take a look at examples/webgl_geometry_hierarchy.html

[kapilreddy]

So basically children and parent properties are used to define hierarchy?? Can two parents have same children?

[mrdoob]

Yes and no.

[kapilreddy]

Still the problem remains how to define pivot of group. I am trying to make a rubik's cube I can now changing grouping of small groups according to mousemove vector but pivot of each group still giving problem.

[mrdoob]

That's an interesting use case. Wouldn't the pivot be the center of the group?

[kapilreddy]

The pivot is pivot of object first in the group and not the center.

[kapilreddy]

http://dl.dropbox.com/u/13195512/rubik/rubikscube.html you can check if its done wrong way here.

[mrdoob]

Hope this illustrates:

var group = new THREE.Object3D();

var geometry = new Cube( 10, 10, 10 );
var material = new THREE.MeshBasicMaterial( { color: 0x00ffff } );

var cube1 = new THREE.Mesh( geometry, material );
cube1.position.x = 30;
cube1.position.z = 30;

group.addChild( cube1 );

var cube2 = new THREE.Mesh( geometry, material );
cube2.position.x = 30;
cube2.position.z = - 30;

group.addChild( cube2 );

var cube3 = new THREE.Mesh( geometry, material );
cube3.position.x = - 30;
cube3.position.z = - 30;

group.addChild( cube3 );

scene.addObject( group );

group.rotation.y += 0.5;

[kapilreddy]

Yes that is ok if i want the pivot to be fixed but as you can imagine pivot and group in case of rubik's cube would be dynamic

[shravanimmy]

i have a wind turbine. i want to rotate the wind turbine. wind turbine is a 3d object. when i am trying to rotating it is getting displaced from it center. the rotation is not perfect. it maybe an issue with my pivot point. pls help

var pointToRotateAround;
var objectToRotate;

var pivot = new THREE.Object3D();
//loading 3d turbine

var loader = new THREE.JSONLoader();
    loader.load("model/fan.js", handle_load11);
    function handle_load11(geometry){
          fan1 = new THREE.Mesh(geometry, material);
          fan1.scale.set(8,8,8);
          position=fan1.position;
          var box = new THREE.Box3().setFromObject( fan1 );
          geometry.applyMatrix( new THREE.Matrix4().makeTranslation(position.x, position.y, position.z) );
          box.center( fan1.position ); // this re-sets the mesh position
         fan1.position.multiplyScalar( -1);
        var axis = new THREE.Vector3(-0.5 ,0, 0 )
         pivot.position= axis;
           //pivot.position=fan1.position;
        pivot.add(fan1);
        scene.add(pivot);

    }

//rotating turbine 

   pivot.rotation.x += .2;

[Mugen87]

@shravanimmy Please use the forum or stackoverflow for help requests.

[arnavzek]

ummm...