Second Life Forums Archive

Consuelo Albanese

Registered User

Join date: 28 Aug 2007

Posts: 13

08-18-2009 09:38

Is there a trick to changing an object textured with an Alpha so that it doesn't suddenly appear behind another Alpha?

Rolig Loon

Not as dumb as I look

Join date: 22 Mar 2007

Posts: 2,482

08-18-2009 10:21

Yes. Don't do it.

This is a well-known challenge, not only in SL but in other systems that use OpenGL architecture (and some that don't as well). When you place two alpha-textured objects close together and in your line of sight, you are almost guaranteed to get a sorting problem. Essentially, your graphics card can't figure out which of the two objects is in front of the other one, so it flickers back and forth between them. (In rough analogy, this is what happens with your brain in RL when you look at things on two transparent surfaces that are in front of each other. Ever try to wash windows and figure out which side has the annoying smudge on it?)

There are certainly ways to minimize the problem, discussed often and at length in the Texturing Tips forum, but the best advice is "Avoid putting alpha-textured objects in front of each other if at all possible."

_____________________

It's hard to tell gender from names around here but if you care, Rolig = she. And I exist only in SL, so don't ask....

Look for my work in XStreetSL at

Argent Stonecutter

Emergency Mustelid

Join date: 20 Sep 2005

Posts: 20,263

08-18-2009 10:35

Gammas are stupid. They all wear green, and Delta children wear khaki. Oh no, I don't want to play with Delta children. And Epsilons are still worse. They're too stupid to be able to read or write. Besides, they wear black, which is such a beastly colour. I'm so glad I'm a Beta. Alpha children wear grey. They work much harder than we do, because they're so frightfully clever. I'm really awfully glad I'm a Beta, because I don't work so hard. And then we are much better than the Gammas and Deltas.

_____________________

Argent Stonecutter - http://globalcausalityviolation.blogspot.com/

"And now I'm going to show you something really cool."

Skyhook Station - http://xrl.us/skyhook23
Coonspiracy Store - http://xrl.us/coonstore

Rolig Loon

Not as dumb as I look

Join date: 22 Mar 2007

Posts: 2,482

08-18-2009 10:43

LOL ... and I thought I was confused. Poor Beta!

_____________________

It's hard to tell gender from names around here but if you care, Rolig = she. And I exist only in SL, so don't ask....

Look for my work in XStreetSL at

Penny Patton

Registered User

Join date: 8 Dec 2005

Posts: 82

08-20-2009 07:45

From what I understand, LL could seriously reduce the problem by letting residents upload 1-bit alpha textures. These are alpha channels that only allow for solid/clear transparency, nothing inbetween like the 32-bit alphas we can use.

Ever notice how linden plants don't flicker like that, despite pretty much being a clump of alpha textures? It's because they're using 1-bit alpha textures. There's a request for this on the Jira that's over a year old, with over 250 votes.

https://jira.secondlife.com/browse/VWR-6713

Welcome to the Second Life Forums Archive

Dueling Alphas

Dueling Alphas
Consuelo Albanese Registered User Join date: 28 Aug 2007 Posts: 13	08-18-2009 09:38 Is there a trick to changing an object textured with an Alpha so that it doesn't suddenly appear behind another Alpha?
Rolig Loon Not as dumb as I look Join date: 22 Mar 2007 Posts: 2,482	08-18-2009 10:21 Yes. Don't do it. This is a well-known challenge, not only in SL but in other systems that use OpenGL architecture (and some that don't as well). When you place two alpha-textured objects close together and in your line of sight, you are almost guaranteed to get a sorting problem. Essentially, your graphics card can't figure out which of the two objects is in front of the other one, so it flickers back and forth between them. (In rough analogy, this is what happens with your brain in RL when you look at things on two transparent surfaces that are in front of each other. Ever try to wash windows and figure out which side has the annoying smudge on it?) There are certainly ways to minimize the problem, discussed often and at length in the Texturing Tips forum, but the best advice is "Avoid putting alpha-textured objects in front of each other if at all possible." _____________________ It's hard to tell gender from names around here but if you care, Rolig = she. And I exist only in SL, so don't ask.... Look for my work in XStreetSL at
Argent Stonecutter Emergency Mustelid Join date: 20 Sep 2005 Posts: 20,263	08-18-2009 10:35 Gammas are stupid. They all wear green, and Delta children wear khaki. Oh no, I don't want to play with Delta children. And Epsilons are still worse. They're too stupid to be able to read or write. Besides, they wear black, which is such a beastly colour. I'm so glad I'm a Beta. Alpha children wear grey. They work much harder than we do, because they're so frightfully clever. I'm really awfully glad I'm a Beta, because I don't work so hard. And then we are much better than the Gammas and Deltas. _____________________ Argent Stonecutter - http://globalcausalityviolation.blogspot.com/ "And now I'm going to show you something really cool." Skyhook Station - http://xrl.us/skyhook23 Coonspiracy Store - http://xrl.us/coonstore
Rolig Loon Not as dumb as I look Join date: 22 Mar 2007 Posts: 2,482	08-18-2009 10:43 LOL ... and I thought I was confused. Poor Beta! _____________________ It's hard to tell gender from names around here but if you care, Rolig = she. And I exist only in SL, so don't ask.... Look for my work in XStreetSL at
Penny Patton Registered User Join date: 8 Dec 2005 Posts: 82	08-20-2009 07:45 From what I understand, LL could seriously reduce the problem by letting residents upload 1-bit alpha textures. These are alpha channels that only allow for solid/clear transparency, nothing inbetween like the 32-bit alphas we can use. Ever notice how linden plants don't flicker like that, despite pretty much being a clump of alpha textures? It's because they're using 1-bit alpha textures. There's a request for this on the Jira that's over a year old, with over 250 votes. https://jira.secondlife.com/browse/VWR-6713