Second Life Forums Archive - weird look dont know how to prevent it

Tyci Kenzo

K2 Owner and Designer

Join date: 8 Dec 2005

Posts: 285

07-27-2006 19:35

im working on a build with my husband and we have windows in part of it but i keep getting weird views and i dont know how to stop it

is it this way with all windows in builds?
is it because of the shape of the area i put the windows in?
is it the particular window textures im using?
ill include the pic to show and maybe you all can help me with this but what is happening is on the fronts of the build we are working on where the windows are we can see thru the walls now even there the windo section is not at

http://photos.me.com/viewimage.php?id=Secondlife/Tyci&folderid=20060327234221&image=0

sorry that was the only place i had available to post a pic at

Chosen Few

Alpha Channel Slave

Join date: 16 Jan 2004

Posts: 7,496

07-27-2006 20:22

What you're seeing is an extremely common issue with what's known as alpha sorting. It happens in nearly all 3D applications, including all video games and most modeling programs, in addition to SL. When two objects with transparency (alpha) overlap in close proximity, OpenGL has trouble determining in what order to draw them (sorting), and they often end up appearing to switch places with eachother depending on current camera angle, cancel eachother out, or present any of a few other seemingly strange effects.

For a more detailed explanation of alpha sorting, check the transparency guide, stickied at the top of the texturing forum. It's covered in the FAQ section.

The only way to prevent it is to be careful not to let alpha-textured objects overlap, or as one game artist said in a recent interview when asked how his company deals with alpha sorting, "we avoid it all costs". With a cylinder like the one in your picture, this can be a challenge, since by its very nature, a hollow cylinder overlaps itself in 3D space as it curves.

I'd recommend making 2 versions of your texture, one at 32-bit (the one you're using now), and one at 24-bit so it has no transparency. Then use multiple cut cylinders put together to form one whole. Keep the 32-bit parts as small as possible, just large enough to fit the windows in. Keep the parts inbetween the windows 24-bit, and most of the sorting problems should disappear. This will eat up some more prims, but there's no good low-prim solution here.

Another option would be to mask the overlap by making the cylinder a bit thicker (less than 95% hollow, maybe 85 or 90%), and then putting some thinner (95% hollow) cut cylinder sections with a 24-bit texture (default is fine for this) inside the walls. This will save a prim or two over the other method, but it's a bit harder to edit.

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Madame Maracas

Not who you think I am...

Join date: 7 Jun 2004

Posts: 1,953

32 & 24 bits, Alpha channel rendering errors & other icky stuffs

07-27-2006 20:22

I'm going to guess that what you're seeing is an alpha-channel texture rendering error that's really annoying.

If one places a texture that has a clear section, like a window, in a larger solid/opaque area, such as one might find where wall surrounds a clear window, SL has trouble deciding if the entire prim is see through or not.

What you end up with is a view of the texture facing you AND what's behind it sorta bleeding through.

How to resolve this? When possible, restrict the clear section of a window and texture to a prim, and then insert it into a solid textured wall/surround. This will leave the clear parts clear and the solid parts solid. Yes this means more prims and that's a dern shame.

Another way you'll see this is if one uses a texture that although it SHOULD be a solid/opaque, it does this front/back inside/out thingie because the texture has been saved to 32 bit (for alpha/clear) instead of 24 bit (for solid/opaque) effects.

I wish I had a happier answer but that's what little I know, good luck!

_____________________

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Kyrah Abattoir

cruelty delight

Join date: 4 Jun 2004

Posts: 2,786

07-28-2006 01:38

it is normal, put one side of a clinder with an alpha, and avoid 2 at all cost

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weird look dont know how to prevent it
Tyci Kenzo K2 Owner and Designer Join date: 8 Dec 2005 Posts: 285	07-27-2006 19:35 im working on a build with my husband and we have windows in part of it but i keep getting weird views and i dont know how to stop it is it this way with all windows in builds? is it because of the shape of the area i put the windows in? is it the particular window textures im using? ill include the pic to show and maybe you all can help me with this but what is happening is on the fronts of the build we are working on where the windows are we can see thru the walls now even there the windo section is not at http://photos.me.com/viewimage.php?id=Secondlife/Tyci&folderid=20060327234221&image=0 sorry that was the only place i had available to post a pic at
Chosen Few Alpha Channel Slave Join date: 16 Jan 2004 Posts: 7,496	07-27-2006 20:22 What you're seeing is an extremely common issue with what's known as alpha sorting. It happens in nearly all 3D applications, including all video games and most modeling programs, in addition to SL. When two objects with transparency (alpha) overlap in close proximity, OpenGL has trouble determining in what order to draw them (sorting), and they often end up appearing to switch places with eachother depending on current camera angle, cancel eachother out, or present any of a few other seemingly strange effects. For a more detailed explanation of alpha sorting, check the transparency guide, stickied at the top of the texturing forum. It's covered in the FAQ section. The only way to prevent it is to be careful not to let alpha-textured objects overlap, or as one game artist said in a recent interview when asked how his company deals with alpha sorting, "we avoid it all costs". With a cylinder like the one in your picture, this can be a challenge, since by its very nature, a hollow cylinder overlaps itself in 3D space as it curves. I'd recommend making 2 versions of your texture, one at 32-bit (the one you're using now), and one at 24-bit so it has no transparency. Then use multiple cut cylinders put together to form one whole. Keep the 32-bit parts as small as possible, just large enough to fit the windows in. Keep the parts inbetween the windows 24-bit, and most of the sorting problems should disappear. This will eat up some more prims, but there's no good low-prim solution here. Another option would be to mask the overlap by making the cylinder a bit thicker (less than 95% hollow, maybe 85 or 90%), and then putting some thinner (95% hollow) cut cylinder sections with a 24-bit texture (default is fine for this) inside the walls. This will save a prim or two over the other method, but it's a bit harder to edit. _____________________ . Land now available for rent in Indigo. Low rates. Quiet, low-lag mainland sim with good neighbors. IM me in-world if you're interested.
Madame Maracas Not who you think I am... Join date: 7 Jun 2004 Posts: 1,953	32 & 24 bits, Alpha channel rendering errors & other icky stuffs 07-27-2006 20:22 I'm going to guess that what you're seeing is an alpha-channel texture rendering error that's really annoying. If one places a texture that has a clear section, like a window, in a larger solid/opaque area, such as one might find where wall surrounds a clear window, SL has trouble deciding if the entire prim is see through or not. What you end up with is a view of the texture facing you AND what's behind it sorta bleeding through. How to resolve this? When possible, restrict the clear section of a window and texture to a prim, and then insert it into a solid textured wall/surround. This will leave the clear parts clear and the solid parts solid. Yes this means more prims and that's a dern shame. Another way you'll see this is if one uses a texture that although it SHOULD be a solid/opaque, it does this front/back inside/out thingie because the texture has been saved to 32 bit (for alpha/clear) instead of 24 bit (for solid/opaque) effects. I wish I had a happier answer but that's what little I know, good luck! _____________________ RadioRadio - http://radioradiosl.com M 6 Hobbes Abattoir T 7 Sezmra Svorag W 4 Brian Mason W 6 Moira Stern W 8 Nala Galatea Th 6 Chet Neurocam F 6 Vertigo Paris F 9 Madame Maracas S 5 Madame Maracas S 8 TriNala Su 6 Trinity Serpentine http://madamemaracas.wordpress.com - Madame Maracas Blaaagh Plurk - http://www.plurk.com/user/MadameMaracas
Kyrah Abattoir cruelty delight Join date: 4 Jun 2004 Posts: 2,786	07-28-2006 01:38 it is normal, put one side of a clinder with an alpha, and avoid 2 at all cost _____________________ tired of XStreetSL? try those! apez http://tinyurl.com/yfm9d5b metalife http://tinyurl.com/yzm3yvw metaverse exchange http://tinyurl.com/yzh7j4a slapt http://tinyurl.com/yfqah9u

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weird look dont know how to prevent it