Scale mesh1, mesh2 automatically change it's position?

Question

Basicially I like to connect the right side of mesh 1 to the left side of mesh 2.

Currently, If I scale mesh1 I have to reposition mesh2 in order to have the same distance as before.

So let's scale mesh 1 to z: 2

var tween = new TWEEN.Tween(mesh1.scale).to({ z: 2 }, 1000).start();
tween.easing(TWEEN.Easing.Elastic.InOut);

In order to have the same distance to mesh 1 as before I have to reposition mesh 2 to z:1.5

var tween = new TWEEN.Tween(mesh2.position).to({ z: 1.5 }, 1000).start();
tween.easing(TWEEN.Easing.Elastic.InOut);

Are there any options in connecting the colored mesh faces. So If I scale mesh 1, mesh 2 automatically change it's position?

...

var geometry = new THREE.BoxGeometry( 1, 1, 1 );


var mesh1 = new THREE.Mesh( geometry, 
new THREE.MeshPhongMaterial({color: 0x222222}));
mesh1 .position.set( 0, 0, 0 );
mesh1 .scale.set( 1, 1, 1 );
scene.add( mesh1 );

var mesh2 = new THREE.Mesh( geometry, 
new THREE.MeshPhongMaterial({color: 0x222222}));
mesh2 .position.set( 0, 0, 1 );
mesh2 .scale.set( 1, 1, 1 );
scene.add( mesh2 );

Answer 1

This is a geometric problem.

I haven't worked with three.js before, but I believe I have a geometric solution.

Consider a third imaginary mesh, mesh3 , such that it is a combination of mesh1 and mesh2 .

That is:

mesh1: position(0, 0, 0), scale(1, 1, 1);
mesh2: position(0, 0, 1), scale(1, 1, 1);
mesh3: position(0, 0, 0), scale(1, 1, 2); // Loosely, mesh3 = mesh1 + mesh2

Now to scale the structure by a scalar k , I propose two approaches:

Approach 1:

1. Scale mesh1 and mesh3 each by k .
2. Compute the difference between mesh3 and mesh1 , meshDiff .
3. Set mesh2 = meshDiff .

Approach 2:

1. Scale mesh3 by k .
2. Compute two halves of mesh3 , mesh31 and mesh32 , such that they are oriented along mesh1 and mesh2 respectively.
3. Set mesh1 = mesh31 and mesh2 = mesh32 .

The approaches are very similar. Keep three.js's API in mind to choose the best approach.

Note: You needn't ever render mesh3 . It only exists as a computational aid.

Generality:

The idea presented above can be used in other situations as well, wherein geometries sharing a common feature need to be scaled.

Hope this helps.

PS: I realize that this answer is a little abstract. Nonetheless, I hope it helps.