THREE.js generate UV coordinate

Question

I am working on importing a model into a scene using the THREE.js OBJ loader.

I know that I am able to import the geometry fine, because when I assign a MeshNormalMaterial to it, it shows up great. However, if I use anything that requires UV coordinates, It gives me the error:

[.WebGLRenderingContext]GL ERROR :GL_INVALID_OPERATION : glDrawElements: attempt to access out of range vertices in attribute 1 

I know this is because the loaded OBJ has no UV coordinates, but I was wondering if there was any way to generate the needed texture coordinates. I have tried

material.needsUpdate = true;
geometry.uvsNeedUpdate = true;
geometry.buffersNeedUpdate = true;

...but to no avail.

Is there any way to automagically generate UV textures using three.js, or do I have to assign the coordinates myself?

Answer 1

To my knowledge there is no automatic way to calculate UV.

You must calculate yourself. Calculate a UV for a plane is quite easy, this site explains how: calculating texture coordinates

For a complex shape, I don't know how. Maybe you could detect planar surface.

EDIT

Here is a sample code for a planar surface (x, y, z) where z = 0:

geometry.computeBoundingBox();

var max = geometry.boundingBox.max,
    min = geometry.boundingBox.min;
var offset = new THREE.Vector2(0 - min.x, 0 - min.y);
var range = new THREE.Vector2(max.x - min.x, max.y - min.y);
var faces = geometry.faces;

geometry.faceVertexUvs[0] = [];

for (var i = 0; i < faces.length ; i++) {

    var v1 = geometry.vertices[faces[i].a], 
        v2 = geometry.vertices[faces[i].b], 
        v3 = geometry.vertices[faces[i].c];

    geometry.faceVertexUvs[0].push([
        new THREE.Vector2((v1.x + offset.x)/range.x ,(v1.y + offset.y)/range.y),
        new THREE.Vector2((v2.x + offset.x)/range.x ,(v2.y + offset.y)/range.y),
        new THREE.Vector2((v3.x + offset.x)/range.x ,(v3.y + offset.y)/range.y)
    ]);
}
geometry.uvsNeedUpdate = true;