[Radiance-general] oconv and rtrace_dc warnings for non-planar vertices

[Greg Ward]

The warnings don't indicate any action, and are only given by  
Radiance because cracks may appear between polygons due to the  
determination of an "average plane" that doesn't pass exactly through  
every point.

-Greg

> From: Thomas Bleicher <tbleicher at arcor.de>
> Date: June 12, 2008 12:16:05 PM PDT
>
> On 11 Jun 2008, at 21:24, Ramana Koti wrote:
>
>> oconv: warning - non-planar verterx for polygon "f_1719_0" (this  
>> happens for 20 or so polygons)
>> rtrace_dc: warning - non-planar vertex for polygon "F_1636 (Can't  
>> see the rest of it, this happens for probably the same polygons  
>> but not in the same order)
>>
>> I used the SketchUp to Radiance su2rad plugin to export geometry  
>> from a sketchup model and I had to start the simulation before  
>> DAYSIM refreshed geometry display since it was taking too long to  
>> do that.
>>
>> How serious are these warnings and why are they occuring?
>
> The export of polygons from Sketchup has only a limited accuracy.  
> This results in some
> cases in polygons where one of the points is outside of the plane  
> defined by the rest
> of the vertices. Radiance has a built in tolerance for these points  
> but when that's exceeded
> the warning is generated and the vertex or the whole polygon  
> ignored in the rendering.
> I'm not sure about the last part but maybe someone else knows better.
>
> Relevance: If the polygon is ignored and it is essential for the  
> geometry (ie a wall of a room)
> then it is relevant. If it's just a tiny piece that doesn't do much  
> for the lighting it's harmless.
>
> To avoid this problem export with the option 'triangulate'. This  
> creates polygons with
> only 3 vertices. Much more polygons in the scene but no warnings.
>
> Regards,
> Thomas