View Full Version : Odd render artifacts in imported model

01-20-2014, 08:37 AM
I picked up a free OBJ model of a copy machine and imported it into Lightwave. When I do test renders there are odd artifacts where some polygons are darker than they are supposed to be and thus far I've been unable to figure out why. I've tried merging polygons and re-triangulating them, merging points, and other stuff and still I get these blotchy renders in some areas and not in others. Does anyone have ideas on why this is and how I might be able to fix it?

Many thanks in advance!


01-20-2014, 08:52 AM
Set the Vertex Normal Map to none and lower the Smooth Threshold.

01-20-2014, 08:54 AM
I think what you are looking at has to do with smoothing. I removed the Vertex normal map and set the smoothing threshold to 20 and that seemed to get rid of the the weird shading that was going on.

edit: beat me to it :)

01-20-2014, 09:46 AM
Wow, never noticed that had been set. D'oh! That fixed me right up, many thanks!

01-21-2014, 04:48 AM
yes itīs most certainly vertex normal maps causing it, for rendering it correctly you must also use real or perspective camera, not classic, but it also depends on how you have set the smoothing angle in
the program the object were made, or within a conversion program such as deep exploration.
otherwise you have to disable vertex maps, but that will also leave you with parts of the model that you cant render so nicely with smooth surfaces.

Also to note something that might help, true art(sensei) has a plugin for dealing with such issues called true obj loader, I never tested it since I worked out a proper workflow anyway with solidworks-deep exploration and exported objects to obj with vertex normal maps correctly rendered, it took quite some time to get it right..but in the end it worked...just needed to set a proper smoothing angle in deep exploration and use perspective cam in lightwave.

Deep exploration is a rather expensive tool though so....
hereīs the link to truearts obj plugin...not sure if it works nowadays properly, so that question you have to forward to sensei.

if you can do without vertex normals, thats fine..since it increases rendertime a lot, and lightwave donīt handle vertex normals so good if there are many of them..it could freeze, and if
you move or edit points in that exported model, the vertex maps probably will get screwed up and so will your renders, rotation of objects might work though.