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Skybox Artifacts


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#1 mbalrog6   Members   -  Reputation: 100

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Posted 16 February 2011 - 01:58 AM

Hello all. I have gone ahead and read a few chapter in advance. I have implemented the skybox content pipeline example in the book. It seems to work fine except that at the top and bottom faces of the skybox, for all sides except the front side a line occurs at the seam. Here is a link to an image of what I am seeing. I have circled the visual artifact in green. I have downloaded the skybox texture from a free sample site and converted it to the format needed for the content processor.

Posted Image


The skybox texture can be found here:

http://dl.dropbox.com/u/9337327/skybox3.png

If anyone can shed some light on why this is happening and how it can be compensated for I would appreciate the help.
thank you.

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#2 Sammie22   Members   -  Reputation: 102

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Posted 17 February 2011 - 01:30 AM

Did you have these issues using the skybox texture provided on the cd? I am working through this chapter now so don't have any input for you beyond checking the texture on the cd and looking for differences (perhaps in size / aspect ratio).

#3 Erik Rufelt   Crossbones+   -  Reputation: 3323

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Posted 17 February 2011 - 06:21 AM

That is caused by bilinear filtering, and wrapping at the edges. Try using clamping instead of wrapping, which should fix part of it. However, some edges might still be visible. The reason is that with bilinear filtering the pixels neighboring the white part of the image are averaged with white when scaled, to give a smooth appearance. Normally this is desired, but when you tile textures in a single larger texture it can give you artifacts. The solution is to put borders along the textures that have the same color as the texture it is supposed to blend with. For example your four images at the top of the skybox texture blend perfectly into each other in the image, so therefore you don't get any artifacts at those edges.

#4 mbalrog6   Members   -  Reputation: 100

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Posted 17 February 2011 - 06:22 PM

That is caused by bilinear filtering, and wrapping at the edges. Try using clamping instead of wrapping, which should fix part of it. However, some edges might still be visible. The reason is that with bilinear filtering the pixels neighboring the white part of the image are averaged with white when scaled, to give a smooth appearance. Normally this is desired, but when you tile textures in a single larger texture it can give you artifacts. The solution is to put borders along the textures that have the same color as the texture it is supposed to blend with. For example your four images at the top of the skybox texture blend perfectly into each other in the image, so therefore you don't get any artifacts at those edges.


Thank you for the information that makes perfect since. I will try fixing that tonight when I get home.




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