Three.js - Scale model with scale.set() or increase model size?

Question

What is the best practise for scaling 3d models in Three.js (or other 3d renderers)?

Here is an example I just faced:

I load a model in and realise the size of the model is too small. I then scale the mesh using mesh.scale.set(2,2,2); and it is perfect size.

What action should I take in this scenario, do I leave it scaled like that (programatically scaled) or do I go back to my 3d modelling software and double the size of the model?

Thanks

Solution

It is not a matter of best practice but rather of optimization. If your mesh will always be scaled, it is better if you do the scaling in your modeling software. That simple statement mesh.scale.set(2,2,2); is a matrix multiplication that needs to happen on each frame rendered. Now maybe your scene does not have much geometry in it in which case you don't care. But as I said it is a matter of optimization. What if your scene had 1000 such meshes or 1000000. That matrix multiplication would need to happen for each one of them. Optimize whenever you can.

Comments

[WestLangley]

gaitat - This is not correct. mesh.scale.set() is called once. By default, mesh.matrix is recomputed each frame anyway, regardless of the value of scale.

[gaitat]

Yes but I assume that even in the interpreted javascript, multiplying by 1 is a no-op while multiplying by 2 is not.

[Peter Ehrlich]

It would be interesting to see a proper performance test demonstrating this... any time I've tried similar things, there's been more randomness in the results than any discernible pattern. Not sure what the best way of running such a test is.

[Agent Zebra]

@PeterEhrlich how would one set up such a performance test? o.O

[Steven Lu]

One thing that I might point out is you should be aware that mesh.scale.set(2,2,2) works while mesh.scale = new THREE.Vector3(2,2,2) does not. The reason is probably some internal caching being done in the mesh object.

[Killroy]

You can "pre-scale" your geometry as well with mesh.geometry.scale(2, 2, 2). This happens only once and modifies the actual vertices in the geometry. Regarding above comment, mesh.scale.copy(new THREE.Vector3(2, 2, 2)) will work. Useful if you're re-using your scale vector.

[1owk3y]

Thanks @Killroy - I was using .geometry.scale.set()... didn't realise you could just .geometry.scale(). Wish your answer was more visible!