Hi,

I will explain.

look at the cone in the first image.
the vertex normals are shown as the lightblue lines.

if you render this object smooth using the vertex normals supplied,
you get ugly shading.

because the renderer will interpolate the vertex normal of the base piece center vertex with the vertex normals of the edges of the base of the cone.







there are 2 solutions to this:

1. split the cone triangles and the base triangles into 2 groups, eg smooth groups.
the renderer still uses the supplied vertex normals, but it does'nt interpolate vertex normals shared between 2 groups during rendering (i'm not talking about remaking / averaging new normals, i'm talking about computing the shading tangent from the vertex normals during raytracing)

this is the solution the the problem here, that's why i'm adding smoothgroup support to octane.

2. split the object into 2 objects, thereby duplicating the shared vertices.
this can be done with the 'edgesplit' modifier in blender, and this is what most of our users do (who use blender).
it solves the problem because you basically end up with 2 objects, eg all the shared vertices between the base and the top of the cone are duplicated at the same positions, but you're model has much more vertices.

these images are an example of the edgesplit (eg nr 2) solution:






the problem with paq's models is that they require solution 1, since moi3d exports them all as single vertices, and you use the smooth groups to create the bounds between what is what during tangent space interpolation.
you can see the wip smoothgroup image posted by phil solves the issue. it's still not perfect because as i said it's a work in progress and i'm not redefining the bounds correctly yet.


Radiance