Today, I "round-tripped" a file from MoI to Rhino 4.0 and back. In Rhino I added a layer, a light, a texture, maybe some viewport stuff. When saving the model in Rhino I chose v4 format... (MoI apparently saved it originally as v3?).

After bringing the file back to MoI, simply pointing the cursor to various places in a viewport causes the display artifacts you can view in the attached jpg. The extraneous triangles sometimes appear in a viewport different from the one with the cursor. Sometimes pointing to an object causes them. Sometimes pointing to an empty part of the viewport causes them. Oddly enough I have a screen shot from the pre-release Rhino v1 days showing the very same sort of artifact.

Both v3 and v4 model files are attached.

No artefact with your 2 files for me :)

The display artifacts shown in that jpg are intermittent. Their appearances depend upon where you place the mouse cursor in a viewport. Not all cursor locations produce the triangle. It's something to do with the v4 file (maybe a superfluous point in the definition of the largest shape), since the original (MoI) version doesn't show the problem. Something is confusing the renderer into thinking there is geometry to render.

Now for the odd thing I just discovered:

Delete any object from the model. Then click undo.

No more display artifact!!!

Unfortunately, after saving the model, then reloading it, the artifact is back.

Thanks for the additional information. I've got a couple of ideas, I'll try to dig into this some more to try and figure it out (probably just after I put out the next beta).

Is this a recurring problem that you have seen with different files too? Or does it seem to be something specific to the geometry of this file?

- Michael