Object Instancing using XTK?
I have seen an instancing example in the following link. http://www.vasava.es/lab/webgl/instancing_batch/
Is it possible to do this using XTK or three.js?
Regarding XTK: XTK is optimized for fewer large objects rather than for a lot of small objects due to the focus on medical imaging data. If you look at the example code you posted you see that they use custom shaders etc. and other optimizations to get the great performance. Three.js might be the right solution to do something like this.
Nevertheless, I quickly did an animation with 1000 cubes in XTK: http://jsfiddle.net/haehn/jjzuD/
If you compare the FPS, you see that XTK is pretty slow in this use case.