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# BG Solarian avatars - seams on head

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## Question

And one more question for all lovers of furry BG Solarian avatars. Why are there seams on the head of this avatar (even on an ultra graphic if it depends on it)?

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I asked the group and they told me that at a low height everything looks better and no seams are visible. I wonder why this happens and will it ever be fixed?

Edited by Tattooshop

## Recommended Posts

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Fixed... depends what you mean by fixed. Mesh can be designed to minimize this problem. It is tedious.

The nature of the problem is in the render-math. For fast rendering small integers are use used. When you see a number like 123.12345 you are seeing the max number of digits in use in SL rendering (I think - it has been awhile since I went through the math).

The position of a vertex may be 0.00000, 0.00000, 0.00000 (x,y,z). If so and you move it to 1,000m altitude it changes to 0.00000, 0.00000, 1,000.0000 and you should notice the 5th place 0 drops off. We get a rounding error if that was any value other than 0.

I am writing in base 10 to make it easier to see. In binary the difference in digits used between 1,000 (11 1110 1000 - 10 places) and 4,000 (1111 1010 0000 - 12 places) is bigger. If you look at the binary and limit the number to the eight left-most significant digits you can see the problem. Trim off the right-most 4 and you trim off a value of 15.

So, if vertices are at values like 0.00000, 0.00000, 1,000.5555 then moving to 4,000m altitude is going to cause vertices to move around.

The SL system is not going to change. To use larger numbers with less round off problems would cause a significant performance hit.

Are designers going to do better? Probably not. There is no reason to tweak every vertex on a seam unless there is an expectation it will be used mostly at high elevations, which avatars and clothes usually aren't.

Going above 1024m elevation trims a digit, above 2048 trims another, above 4095 trims a third digit. The Lab considers 4095 the ceiling. You can go above that but expect problems.

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