Put this in your component .MouseDown Event:

Dim o as Object = helixViewport.FindNearestVisual(e.GetPosition(helixViewport))

Yes, its possible.

If you work with a complex material, you need to create a MaterialGroup and Add all materials that will make your final material.

To apply the material in your model, you need to do this (Vb.net)

TryCast(mObj.Content, GeometryModel3D).Material = MaterialGroup

TryCast(mObj.Content, GeometryModel3D).BackMaterial = MaterialGroup

If you don't need back, just does not use them.

Example Basic Material with Image:

Dim b As New ImageBrush(TryCast(myImage, BitmapImage))

The properties Normals, TextureCoord and Positions are private in Helix DLL, but you can change the code and rebuild, or you can create your own class in your code, copying the code from helix.

The helix works with meshs, so, after you importer the .obj, you have a model. So, you don't work no more with the obj file. You can edit and after export again to another .obj.

Other thing thats important remember: If the obj does not have the normals vector, you have to generate them. When you open the .obj in notepad, you can see if haves normals or not.

A mesh is basically defined for positions, triangleIndices and textureCoord. But you can define the vectors normals too, to build a completed mesh. You can define de normals to each position or to each face, thats depends how do you want your model.

I will explain how works MeshBuilder Class:

1) Positions - Collection of vertices

2) TriangleIndices - Collection of indices from de list of positions. Ex: 1 3 2 means that will be build a triangle with the position 1, 3 and 2 from the list of positions, in this order. (The order has influence to decide if the triangle is in back-side or front-side)

3) TextureCoord - Collection of texture coord. The texture coord works with a point (2D - UV coord)

4) Normals - Collection of vectors normals. The vectors normals has big influence in your mesh. I recommend you to study this, like texture coordinates too.

This is the basic to programer 3D.

To zoom Extents:

CameraHelper.ZoomExtents(helix.Camera, helix.Viewport, 1000)

To change Camera:

cameraPerspective.LookDirection = New Vector3D(0, -10, 0)