Question regarding large, non-repeating textures/surfaces

Alrighty,

I have a 10x10m surface.
I created a large texture (no repeats) for this surface at three sizes for troubleshooting purposes:
512x512
1024x1024
2048x2048

Basically what seems to be happening (and this might just be my vid card) is that the SL engine is intermittantly blurring the texture. This is not a download problem, since I've viewed each texture in its own window and also at higher resolution on the surface. I tried each texture to see if it rendered differently, and the 512x512 is not detailed enough, the 1024x1024 is not bad, and the 2048x2048 takes forever to download (obviously). Each texture suffers from intermittant blurring, even if the camera is not moving.

Any thoughts on this? Is it my vid card? A SL rendering engine issue? Is this a known problem and is there any workaround?

..as far as I know, SL automatically reduces the resolution to 500x500 when you upload something. I know that's the way that it used to be. Not sure if that's still the case. If you're seeing a difference in resolution, that probably has to do with your file compression. But as for the blurring issue, I can't really tell you.

Zero,
i have found the following to work: check your texture scaling. you probably have repeats in the textures along the thinner sides of your prim that are in the ballpark of 20x20- if that is so, and the larger faces are scaled 1x1, then you will have the rez/blur/rez issue.
if you grab all surfaces and make them 1x1, it will stop.
i dont know why this is, but its always worked for me

hope that fixes it for you!

Thanks for the reply The 512x512 and 1024x1024 file were uncompressed JPGs, and the 1024x1024 showed more detail. Also I've seen textures that are rectangular in proportion. So I think there are multiple resolutions and sizes allowed, but I always try to keep mine a multiple of 4.

Thanks, I'll have to try this. What I am texturing is a 10x10 platform, and the tricky part is that while the top of it is one texture, the sides are separate textures, but I think I might be able to cheat it as you've described. I'll let you know how it worked out

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All texture measurements are powers of two (2,4,8,16,32,64,128,256,512,1024,204. SL may have a lower and upper size limit... Probably just upper. The images do not have to be square, but both dimensions will be stored as a power of two. If you upload something in an unsupported size, SL will increase that size to a power of two.

So if you upload something that's 128x200, the 128 is okay, but the 200 will be stretched up to 256 when saved on SL's data servers. The image is also re-compressed into JPEG2000 format (supposedly) which uses wavelet compression (which we KNOW is used).

Wavelet compression lets the image load in a graceful manner, starting out blurry and getting progressively sharper and clearer until the whole thing is received. It also permits MUCH higher compression ratios without as much loss in quality.

The blurring you are seeing, however, is a glitch in the Level of Detail (LoD) rendering in the SL engine. Nephilaine is right as to the cause, I believe. Make sure all faces of your prim have similar repeat resolutions if they have the same texture. Either give very small faces the same repeats settings, or a different texture to prevent the intermittent blurring effect.

Tiger, that's awesome technical info, thanks for posting it! Where'd you come across the details?

EDIT: Making all faces of the prim use the same texture at zero repeats stopped the LOD problem. Thanks for the tips, folks You gotta check out my awesome floor at The Secret Lair, Janus (215, 224)

I'm a game programmer in RL, but a lot of this info has been collected from previous forum postings, or open knowledge about graphics formats. Glad it interested you.