MoI’s Sexy Graphics – Part 3

<< Part 2

In the previous part of this series I mentioned a few features of MoI’s graphics engine dealing with the display of curves. In the next couple of parts, I will mention a couple of sweet things about the display of surfaces.

Probably the most wonderful thing about MoI’s graphics engine is it mesher or tessellator. Solids are made up of smooth NURBS surfaces that are trimmed by edges. However, in order to show the 3D model on a 2D display such as a monitor you need to tessellate each individual NURBS surface into a bunch of triangles. These triangles are then colored depending upon their location and angle with respect to the eye and other factors like lighting, etc. MoI has a custom coded surface tessellator which is highly optimized for speed. This allows MoI to produce a much finer and more detailed tessellation by default than is commonly done in CAD programs. This helps to give an overall smoother looking display and also makes it easier to spot surface defects which can otherwise be easily hidden with a display mesh that is too rough.

Michael sent me a SAT file that someone posted on the MoI forum that was created using an ACIS based modeler. Upon loading the file into MoI, he  immediately noticed that the fillet surface quality was not that great. This particular fillet was coming close to the maximum radius value before it would become self-intersecting and the fillet got kind of bunched up and lumpy in the area where it was approaching self-intersection.

The interesting thing was that the user was not able to see those surface defects in his own ACIS based modeler because the display mesh tessellation was too coarse in there. It basically used too few polygons in that area and so the little ripples were totally obscured. Even the other program’s “analysis mode” tools did not tessellate it heavily enough to see the defects. Meanwhile in MoI they are easily visible in just the regular view.

I opened the SAT file in SolidWorks 2010 and this is what I saw.

This goes back to the point I made in part 1 of this series. Let alone the fact that I cannot see the problem. The reflections that make the part “look real” actually end up confusing me all the more. This is what the zebra analysis in SolidWorks looked like.

Part 4 >>




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