Speed up render extraction time by changing `Process 2sided faces` option

Hi All

I have noticed that within the Process 2 sided faces option in `special` menu of setup dialog the factory default is now `when front and back materials are defined for a face`(I am not sure if it was always this). If you have no need to render both sides of faces switching to the `never - use side with material` will drastically speed up the geometric extraction process prior to the render window appearing.

Render time was very slightly slower with the `never` option but I am sure this will differ to model content.

Thanks

Boothy

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Permalink Reply by Render Plus on April 3, 2011 at 7:39am

There may be a problem here. I will take a look. It looks like we are grabbing some faces twice. If so, we will be able to speed things up.

The default is to use both sides if both sides have non-default materials. This should work well. But we may have a bug in our extract logic.

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Permalink Reply by Render Plus on April 3, 2011 at 8:37am

I was confused when I used statistics to check the number of faces in a simple model - a cube - the right answer is 12 (we have to send 2 triangles for each rectangle in SketchUp). So it was working right when I thought it was creating too many "faces".

If you have time to try this again, use the Statistics display (right click on title of rendering window) to see if we extracting too many faces in one of the two modes. If we are, we need to try to see what object is extracting too many faces.

If it turns out you have some geometry with materials on both sides of faces where the material on one side is always invisible, then you could replace the inside material with the default material. However, if you apply materials to groups of component instances, then this can get much trickier.

If "Never" works best for you, you should use it. (It should work better for models with fewer problems) However, if it has more "faces" then there is some other problem we should fix.

I grabbed a "random" model from the 3D warehouse, (not a good text of anything), and "Never" and the default found the same number of faces.

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Permalink Reply by Boothy on April 3, 2011 at 8:58am

Hi Al

Please see image below - same model with the 2 different settings - I thought things have slowed up a bit lately - I had only noticed this when I switched options and found extractions so so so much faster - this is the same on all models tried over last week

Boothy

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Permalink Reply by Render Plus on April 3, 2011 at 10:11am

The 'Never' statistics show fewer faces, which is expected. But does not explain why the 'Never' rendering took longer in the previous post.

See if you can isolate, using layers, or "Render Selection" which element in your model is creating the extra faces. Then we can examine it to see if we can make it render better. (Putting materials on both sides of a face should cause the 'Front and Back" option to create more faces. But it will be helpful to see which item is the culprit)

I will do some other tests to see why the "Front and Back" option is taking longer.