Hey Michael,

Can you please help us out? We're trying to make Octane Render a very affordable and powerful renderer for all modeling programs. We're trying to improve our obj import of MOI3D meshes.

Radiance, the author of Octane Render, has posted the following in a discussion with PAQ on the Octane forum. Can you post whether we're missing something or not?



"i really don't understand.

here's a simple low poly ball.
half the normals are inversed. (the vertex normals)

i export it to an OBJ:



that's correct. the vertex normals are exported to the OBJ, they are read by octane and used for rendering.
the image looks ugly, but it's correct as half the normals point the wrong way.

there is no recalculation of these going on at all, they are used as they are read.

the blender file is :

___________________________________________

# Blender3D v248 OBJ File:
# www.blender3d.org
mtllib invball.mtl
o Sphere
v 0.382683 0.923880 -0.000000

...

vt 0.000000 0.000000 0.0

...

vn -1.000000 0.000000 0.000000

...

usemtl Material.001
s 1
f 37/1/1 7/2/2 8/3/3
f 1/4/4 15/5/1 14/6/5
f 14/7/5 15/8/1 16/9/6

...

________________________________


which is identical to the moi3d file paq posted:

_________________________________

mtllib SuperBall.mtl
o object1
g object1
v 1.29307735 3.62458663 -1.09101924

...

vt 0.00645550 0.11863773

...

vn -0.10859368 0.00000000 0.99408622

...

s 1
usemtl Default
f 1/1/1 2/2/2 3/3/3
f 671/3039/671 3/3036/3 2447/3041/2478
f 2446/3040/2477 672/3038/672 2447/3041/2478

_________________________________


There's nothing else, that's the way OBJ works.

Maybe the problem simply does'nt exist and it's an artifact that presents itself due to the missing smoothgroups ?

Imagine if you have 2 polygons that are connected by a shallow angle,
they should be separated into 2 groups otherwise they will be interpolated and you get shading artifacts.

imagine if one of these 2 normals is on the other side, this will give you strange black shading artifacts.
it's either due to the missing support for smooth groups, or something else.

can someone ask the moi3d implementer ? show him this post and ask him if he maybe exports OBJ's in other ways in certain scenarios ?
the OBJ provided by paq is %100 identical in syntax / structure to my blender example which works %100, except for the missing smoothgroups.

Radiance"


Can you comment on this? I know that you have had experience with other rendering engines and how they handled (or mishandled) vertex data. Can you shed any light on this issue?

Thanks if you can.

Phil