On Tue, 11 May 2004 15:59:50 -0500, Skip Talbot <sta### [at] uiucedu> wrote:
> The setup:  A cylinder intersects a sphere, both filled with scattering
> media.  However, when I use an empty density for the cylinder (removing 
> all
> media) it still casts some sort of ghost in the sphere.  This effect is
> present no matter what density is used, and is problematic when you don't
> want the cylinder's seem present.  Is there anyway to remedy this 
> problem?


Increasing either 'intervals' or 'samples' seems to help, but at a big 
cost in terms of render time.

The attached images are as follows:
1 - Unmodified scene
2 - samples 200, 200
3 - intervals 20

Render times were as follows:
1 - 9 s
2 - 72 s
3 - 330 s

If you look really closely, you can just make out a very faint outline of 
the cylinder on the left side of the sphere in the two "improved" images. 
The one with increased 'samples' also shows bright spots at the top and 
bottom.

Also note that increasing either 'samples' or 'intervals' makes the sphere 
darker. I do not know why this is so, but it happens regardless of the 
cylinder's presence (the darkening effect happens even if you remove the 
cylinder altogether).

To conclude: media is tricky stuff...


---
FE

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Attachments:
Download 'media_interaction_test_original.png' (38 KB) Download 'media_interaction_test_samples_200.png' (38 KB) Download 'media_interaction_test_intervals_20.png' (38 KB)

Preview of image 'media_interaction_test_original.png'

Preview of image 'media_interaction_test_samples_200.png'

Preview of image 'media_interaction_test_intervals_20.png'