Building a structure with transparent windows

I'm new to building and textures in SL and am looking for general guidelines and best practices about how people create buildings in SL. I'm having difficulty finding anything beyond the most basic info.

I am planning to create a building that will have windows. Based on the research I've done, it seems I should create the building by using the least amount of prims. I can use fewer prims if I use a texture for the outside details of the building. If I use a texture, I can make the building's windows transparent in my PhotoShop texture, using a 32-bit .TGA file. Is that how windows in a building are generally accomplished?

Would I then create a second texture to use for the inside walls of the building that has transparent window areas that line up at the same/reverse spots? Is that how it is usually done? If a non-transparent part of the texture on the outside face overlaps a transparent part of the texture on the inside wall, does that create a problem?

For discussion purposes, if an outside wall is made up of 4 prims that are each 10m x 10 m, should I create one 1024x1024 texture that will be used on all 4 of those prims to display the complete face of the building?

Thanks for any answers you can provide.

You're on the right track. That's the low-prim way to add windows to a building.

There are tricsk for making walls with holes in them for more realistic windows, but it nearly always takes more prims -- usually, considerably more prims.

The problem with using textures alone is that the edges of the window are infinitely thin. That is, there's no window sill, etc. This is entirely acceptable for many buildings; it's a realism vs. prim count tradeoff.

Interestingly enough, when using textures, you don't have to make sure the outside windows are in the same place as the inside ones. Realism requires that you do, but I've seen cases where I wouldn't worry about this kind of discrepancy.

For a 40x10 wall, consider using a 40x10 megaprim if possible, and using the same texture repeated 4 times. You can buy packs of megaprims on XstreetSL; for building purposes I recommend Zawgoth's and the 7000 prim packs. The 7000 pack is nicely organized so it's easy to find what you're looking for, and the Zawgoth provides a number that don't fit into the organization scheme of the 7000 pack. These are freebies or dollarbies and full perms.

Unless your walls are very highly detailed, you might consider doing your customers a favor by using 512x512 rather than 1024x1024. That's 4 times as fast to download. A key thing to think is how *many* big textures you'll need. If you're clever with your textures, you can use a single 1024x1024 with different sections, applied differently (using offsets and repeats to show the part you want where you want it). In that case, if you can use one 1024 texture to replace 4 or more 512x512 textures, it's a clear win for your customers, at a bit of extra effort on your part.

The best buildings not only look beautiful, they also rez quickly and use the fewest and smallest textures possible to achieve the effect.

I highly recommend going to Barnsworth Anubis's store and buying at least one building to see how BA uses textures wisely, minimizing the number that need to be loaded while providing a variety of subtle but impressive effects. Also a number of clever building techniques, though perhaps not the particular one you're asking about. BA stuff tends to be prim-built, effectively using each prim with very little waste, but not nearly as low-prim as you can get using textures holes for windows.

(Wioth a friend's help, I just revamped BA's Trocadero, removing over 100 of it's 400 prims and then adding about 60 to get a second floor, for my new poseball shop. The savings came at a notable cost in architectural detail but suits my purposes while retaining the overall impression. I was very impressed with the architectural skill with which the building was designed, not to mention the careful application of a surprisingly small number of textures. The prim count on this little palace is appropriate for the size of lot where it would normally belong, but I'm squeezing it into a little 4k lot.)

Creating windows as intergral parts of walls certainly saves prims, as you suggest, but it often creates a nasty problem when other objects with an alpha channel are in line of sight. Trees outside, or high heels inside interfere with the alpha texture in the wall and you get a strange flickering effect that we knoiw and love as the "alpha sorting glitch." Unless you really need to conserve prims, it is often wiser to build walls with real openings for windows and doors and then apply 24 bit textures to the walls.

See the excellent discussion at /8/1d/273543/1.html and then take a look at some of the threads referenced in it.

BTW, PLEASE don't use a 1024x1024 texture if you can avoid it. It will take ages to rez for some people and will just annoy them (and they won't get to see your beautiful texture). Better to use a smaller texture and repeat it or, if you don't mind a drop in resolution, stretch it.

Thank you Lear and Rolig for your responses. I'm trying to get an understanding of the degree of pixel detail necessary to create a wall which would be the side of a typical house (maybe 20 m x 20 m?).

Does a 512 x 512 texture provide enough detail for one entire side of a typical house? Likewise, is one well-designed 1024x1024 texture sufficient to include the textures that would be used for all 4 sides of a typical house and still look good?

Thanks for the tip about there being no window sills if I use a transparent texture to create the windows... I didn't think about that. And thanks, too, for the tip about the alpha sorting glitch. I'll check out the megaprims.

So, what is the 'best practice'? To leave actual openings for windows, or to use transparent textures? If leaving actual openings, do you use hollow prims to do that?

Thanks again.

I really encourage you to read through that link I posted earlier, because some of your questions were discussed there pretty well. Also, read through the sticky on transparency and alpha textures as well as the sticky on file sizes and formats, both at the top of this forum. They have a wealth of valuable observations about dealing with transparency and navigating questions of resolution and file integrity in SL. While you're at it, start digging through the archives in this forum and in Building Tips. Questions like yours have a way of cropping up on a regular basis, and there are always new (and more enlightened) answers each time they arise.

When it comes right down to it, many answers to your questions are subjective. How much detail do you need on the side of a house? Well, that depends on (a) how much time you think the average person is going to spend looking at it and (b) how finicky you are. I tend to feel that it's important to emphasize detail on textures that people need to focus on for a while (tapestries, posters with lots of text, etc.) but to forego detail on textures that people will consider "nice background." Frankly, I get VERY annoyed when a texture takes ages to rez ..... and then I discover that it was just another "nice" wall.

"Best practice" is tough to nail down. I think you will find that the most attractive builds leave actual holes for windows and doors instead of drawing them as transparent areas in solid walls. The big advantages, other than avoiding the alpha sorting glitch, are that you can resize them and move them around fairly easily if you need to, and you can create sills, casings, lintels, etc. that have a greater 3D look. Having said that, there are some very attractive builds that use transparent textures to good avantage .... and save on prims.

As to your question about using hollow prims.... yes, you can certainly do that. It can save prims and is fairly fast. The hole in a hollow prim is always centered on the Z-axis, so you may still need to frame around it to get proper placement in your wall, but that's a very minor challenge.

Good luck with building/texturing in SL. Wander around and see how other people are tackling your own building challenges. There's some neat stuff out there.

Thanks again, Rolig. I've checked out the forum URLs you included. I guess I'm leaning toward building with prims now, rather than trying the transparent textures.

Wise move


and .. no 999 pack of textures for you then.

Everything is a compromise in SL, and windows in buildings are en excellent example. You can do alpha texture windows and save prims, and the trade off is that the edges are thin and you risk alpha channel sorting issues. The latter can be particularly irksome in buildings given how much clothing and hair uses textures with alpha channels these days.

So the real answer is...it depends. It depends on what works best for your specific application. A good example are some cathedral builds out there. These use a huge number of prims, on average, but in most cases you will see that for the stained glass windows, frames, and surrounding walls they use alpha channels. Why? Because from where you are in the building, looking up at them, you will never see how thin that particular wall is, and you'll never be close enough or have your viewer at such an angle that the you get sorting issues with other alpha textures. So in these high prim builds, the use of alpha textures is the right choice for that particular application.

Regarding texture optimization, another tactic for you to try takes advantage of the fact that one 1024x1024 texture is more efficient than 4 512x512 textures as it requires 1/4 the connections. So, when you can, put 4 512x512 textures into one 1024x1024 file and then choose which one you want on any given face by adjusting positioning and tiling settings. I once created an object that used 16 different textures, all of them aggregated into one large file.

And again, the size of the texture that you use for any given size surface is not cut and dried. The right choice depends on how close viewers get to the surface, the level of detail of the texture in the file, lighting, prim properties (shininess, glow, etc.).

Thanks for the additional clarification, Heather. I've been reading about texture sheets on some other threads and websites. I plan to give that a try.