Quick tip for tessellation issues

[Speedster]

Most NURBS based CAD displays some tessellation, or faceting, on round features, with SolidWorks among the worst.  It's a function of size.  A small hole will be worse than a large hole.

Yesterday I was rendering a clear acrylic microtitre plate, like a petri dish, with multiple small 1mm diameter wells.  Looked awful.

I simply scaled it up 600% in SolidWorks, and rendered it out.  Looked great!  This tip will work easily on an individual part, but if the part is critical, and in an assembly, then everything would have to be up-scaled as well. Or possibly imported then rescaled in KeyShot?  Note that the scaling has to be in native CAD, not in KeyShot.

Bill G

[hugo]

If I'm doing rescaling does that not mean I'm also adding more geometry to the original object?

[Ruckus]

The only way to remove faceting from your polygonal geometry is to add more polygons, so yes you will "add more geometry".  It can be a tricky balancing act. 

Note: normally you tighten up the tessellation tolerances in you CAD/modeling program, but Bill hit on great idea for those applications that don't offer an easy UI for tessellation control. 

[hugo]

but Bill hit on great idea for those applications that don't offer an easy UI for tessellation control. 

I'm not quite clear on how this is going to work, unless Solidworks has a special way of handling scaling?
In C4D saving a rescaled .obj file does not add any greater control over tessellation. No addition geometry is added and
the newly exported .obj file is still almost the same size. The rendering results are not any better. 

[thomasteger]

Did you make sure to check "calculate normals" inside the import dialog?

[TpwUK]

Hi Hugo, you can't tessellate a mesh object such as OBJ, you would need to add smoothing groups up sub-divisions, tessellation is for NURBS based models, which are then converted into an OBJ type mesh by KS on import.

Martin

[Ruckus]

... a rescaled .obj file does not add any greater control over tessellation. No addition geometry is added and
the newly exported .obj file is still almost the same size. The rendering results are not any better.

Correct.  OBJ is already a tessellated format, so scaling up a triangle just gets you bigger triangle.  And like Martin said, you can't re-tessellate tessellated geometry.  (At least not in any useful way)

You will need to go back to your "math data" (the true curves, surfaces, solids) and re-tessellate those.  Or if the original geometry was modeled in quads, go back to that & create more subdivisions.

[br3ttman]

This is a nice discussion on this topic.  Typically I get really nice model translation from ProE to KeyShot just by adjusting the tessellation upon import to KeyShot.  If, however, I have really tiny features in ProE, I can also adjust that model accuracy in ProE prior to export.  The greater the accuracy, the higher the triangles, and the larger the file becomes in KeyShot.  Sometimes I need to perform a couple practice imports to get the resolution I want for renderings yet still keep the file small in KeyShot, especially when building and rendering complex scenes.

With respect to Solidworks, I understand you can also increase the "image quality" under options/document properties and then save the SolidWorks file prior to export to basically encode the desired higher resolution with the model file.  Does this accomplish the same thing Bill is doing when he scales up his model 6x for greater definition?  And if so, does anyone have a good rule of thumb they follow?  I have similar resolution problems when exporting SolidWorks for rapid prototypes.

[m2tts]

The "image quality" settings in SW do increase the tessellation of the model for better detail. How and or if Keyshot still uses this tessellation i don't know. It used to. I usually have my setting on the border of the red-zone (in SW). I have a Quadro graphics card that can handle this.

For exporting STL's you have to use the "options" tab in the "save as" dialog to adjust the settings for the quality of the STL mesh. It is handled separately from the graphics mesh.

[Speedster]

I understand you can also increase the "image quality" under options/document properties and then save the SolidWorks file prior to export to basically encode the desired higher resolution with the model file.  Does this accomplish the same thing Bill is doing when he scales up his model 6x for greater definition?

Unfortunately, no.  I always set the SolidWorks "image quality" slider to just on the edge of red- you can do higher, but there's no improvement.  But then, depending on feature size (such as my 1 mm microtitre wells) it still tessellates heavily on import.  So the 400% to 600% scaling has been my only option so far.  Works fine for isolated uses, but should never be used on a large part or assembly unless you are running a Cray Super Computer!

I know a number of requests, including mine, are into SolidWorks to kick the image and export quality in the butt.  But they just don't understand I guess that many of us are using their product for high-end rendering, so no action on this so far.

Bill G