[vtkusers] ... An strange rendering?

[nugg]

Hi Amy,


Amy Squillacote-3 wrote:
> 
> We saw something similar last week when rendering an OBJ. Have you 
> verified that the normals in your OBJ model are pointing outward? In our 
> case, we saw this strange behavior because the normals were pointing 
> inward instead. (Using a vtkGlyph3D filter with a vtkArrowSource as the 
> glyph source will show this visually.)
> 
> I didnt test it. In case that you are right, how could I change the
> normals
> to be pointing outward?
> 
> A lot of thanks.
> 
> - Amy
> 
> jsl n wrote:
>> Hi friends,
>>
>>   I've just the following problem when rendering a .OBJ mesh. The first
>> attached
>> screenshot is obtained with the following setup for the VTK's camera:
>>
>> camera->SetFocalPoint(0, 0, 0);
>> camera->SetPosition(0, 0, 5.1);
>> camera->ComputeViewPlaneNormal();
>> camera->SetViewUp(0, 1, 0);
>> camera->SetViewAngle(22.2);
>>
>> It looks right...
>>
>> The point is that changing the SetPosition() method as following:
>>
>> camera->SetFocalPoint(0, 0, 0);
>> camera->SetPosition(0, 0, -5.1);  // Here is the only change.
>> camera->ComputeViewPlaneNormal();
>> camera->SetViewUp(0, 1, 0);
>> camera->SetViewAngle(22.2);
>>
>> rendering becomes messed up (backfaces and bad z-fighting), as depicted
>> in the
>> second attached screenshot. Why placing the camera position in the
>> Z-negative
>> gets wrong results?
>>
>> I'd be so grateful with you for any advice.
>> _________________________________________________________________
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> 
> -- 
> Amy Squillacote                    Phone: (256) 726-4839
> Computer Scientist                 Fax: (256) 726-4806
> CFD Research Corporation           Web: http://www.cfdrc.com
> 215 Wynn Drive, Suite 501
> Huntsville, AL  35805
> 
> 
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