threejs selecting different parts of a mesh - three.js

Question

I'm using THREE.js. I have a model of a human that I want to be able to select different portions of. For example, if you click on one of the legs a particular action will be executed. My original idea was to split the model up into separate meshes and then use raytracing to determine which object was selected. But now when i render the scene, the shading along the edges of each mesh doesn't blend with adjoining meshes. This leaves ragged looking lines across the model between selectable portions. Is there a way to blend the shading between the mesh pieces I've created? Or is there a better way to select part of a mesh other than creating separate meshes? I have some programming experience, but this is the first time I've tried to use three.js. Any insight would be greatly appreciated.

Answer 1

You may create additional attribute for each triangle, that would be color of the bodypart that it belongs to. So, all triangles of the left leg would be red, all triangles of right leg would be blue etc.
Render your model normally, and add second pass where you would render triangles colored in the way described above, so no shading at all. Then, you could get your mouse position where the user clicked and look up in that bodypart-colored framebuffer and just check the pixel color on the place where user clicked.
This technique of picking 3d objects by assigning them different colors, rendering those colors to another texture and then checking color of clicked pixel is quite common, although it has some flaws. On the other hand, neither is ray testing absolutely accurate.
I believe that this demo runs actually based on that concept - demo.

Answer 2

var aiGeojj = new t.CubeGeometry(30, 30, 30);
var uprighters = Math.floor((Math.random() * 11));
var aiMaterialjj = new t.MeshBasicMaterial({ map: t.ImageUtils.loadTexture('images/images_bots/greenbot/upright/' + uprighters + '.gif'), opacity: 0, transparent: true });
var ojj= new t.Mesh(aiGeojj, aiMaterialjj);
ojj.limbs = [];
ojj.trunk = [];
var aiGeojjkey2c = new t.CubeGeometry(50, 50, 50);
var uprightersc = Math.floor((Math.random() * 11));
var aiMaterialjjc = new t.MeshBasicMaterial({ map: t.ImageUtils.loadTexture('images/images_bots/greenbot/upright/' + uprightersc + '.gif'), opacity: 1, transparent: true });
var ojjkey2c = new t.Mesh(aiGeojjkey2c, aiMaterialjjc);
ojjkey2c.id = "hiworld";
ojj.add(ojjkey2c);
ojj.trunk.push(ojjkey2c);
for( var you = 0; you < ojj.length; you++){
for( var youb = 0; youb < ojj[you].trunk.length; youb++){
window.alert( ojj[you].trunk[youb].id);
}
}