Thin wall buildings - why?

While I have rezzed other people's builds, I have not worked that much with creating things (just signs and simple stuff) or textures (other than slowly finding out how to get the number of repeats on an item to look right). So my questions is this:

Some builders, like Greatscott McMillan, have nice thick walls that you have to camera control to look through or around. Others have buildings that the windows shift on you and prims from outside show through, depending on the angles. Some the windows inside don't match the windows outside (so if you hang blinds, they move in relation to the windows, depending on angles and only fit from one side).

The two parter is: 1) what specifically causes the thin wall problem and 2) do they really benefit from this in anyway, or is it sloppy building? (And if this explains why some people make flowers and plants that come and go with the angle, while others have nice, substantial ones that stay regardless...)

My simple signs with textures don't have this issue, and they are one prim and simple as it comes. So why do this?

Wasn't aproblem when I owned and could choose my building, but its a pain when a nice place to rent has buildings with this defect.

It is not a matter of thickness. It is a matter of whether or not the texture of the wall itself has transparency built into it. Even a .01 thick wall with a completely opaque texture will not show other objects through it. If your wall texture has windows in it, this is prone to happen.

Yes, using alpha texture windows can make even a 5 meter thick wall appear paper thin. There are techniques that can be used to solve this, but since most use alpha texture windows to keep prim counts low, they are unlikely to use these techniques since they require the use of more prims

Builds where you don't see this flickering at different angles likely don't use alpha textures and instead just use prims to form the geometry.

So it isn't in the single item, but because it takes prims to build around the windows rather than include them in one. So they want to show a lot of windows on the cheap...

OK. Thanks.

The reason you probably see correlation between thin walls and and alpha textures is because both techniques help buildings that are designed for small land.

If one is limited to 512 sq m, the thickness of the walls has a huge impact upon the interior space available inside the building.

Likewise, if one is limited to 117 prims, one has to find as many ways possible to make one prim do the work of several. Cutting windows out of prims with alpha textures is a prim-saver. (Not necessarily the most efficient or prettiest way to make a wall with windows, but it does save prims.

With more space and prims, one has more options when it comes to design techniques.

Actually by adding windows as a transparent part of a whole-wall alpha texture 'on the cheap' is doing customers a service as it means the building is made from fewer prims, leaving more for the customer to use for other things.

I built my home with alpha texture walls to save prims and I get a bit of the clashing texture problem, but I can live with it!!!

Also, no matter how thick you make the wall prim, if you have an alpha textured wall and look through the window, the wall will appear to have no thickness at all. This is because you can't see the back side of the far surface of the wall, and the "hole" made by the alpha-mapped window has no edge thickness to it.

In some of my low-prim buildings I actually spent one extra prim per window to embed a prim "windowsill" inside the wall. It was a hollow cube prim, sized so the inside surface matched up with the window edges, and the thickness was just a hair less than the wall thickness.

Most builders who make alpha mapped walls where the window on one side doesn't line up with the window on the other side have mixed and matched interior and exterior textures from diferent texture artists. There are not many commercially available sets of textures that have both the inside and the outside of a wall, perfectly matched, because to make those textures, the artist pretty much needs to know precisely how the structure will be built from prims. So a custom builder who makes her/his own textures can do it, but a beginning builder who is buying off the shelf textures or using freebies will have a much harder time getting things to line up perfectly.

Alpha for the sake of prim saving is never a "service", the cost of rendering an alpha wall can be orders of magnitude larger than rendering a solid wall since the first doesn't occlude at all while the second does.

First you need to render as if the wall isn't there so that means when you're inside you render the entire outside world and when you're outside you render the entire interior. Then add alpha sorting and alpha rendering in multiple passes and the performance difference can be immense.

If you're going to use an alpha-based wall you really should be making sure that it actually does still occlude by hiding solid prims inside the wall (except for the transparent part obviously).

More on my alpha textured walls. They do have separate prim window frames made from hollowed and thinned down cubes, so the window openings appear to have some thickness. I've still made 3 prims do the job of about 6, though.

OK, I concede that there are downsides to alphas - I know - I live with them all round me, but my home would look much more boring if I just used solid prims to do the job as I'd run out of my allowance.

Unfortunately, 99% of the customer base that buys houses would rather have the extra prims for their furniture and accessories over rendering faster. Most builders would rather make the real deal and not use alphas at all, but customers are looking at prim count and making their purchasing decisions based on that.

And then turn around and complain how laggy SL is .

The one test case I tried a while back was about 50% FPS difference between alpha and alpha with solid prims hidden in the wall to provide occlusion (5.5fps vs 9.5fps and 8.8fps vs 17.7fps). It's not representative for anything but that particular build in that spot, but it shows just how bad it can get just to save a 2 or 3 prims.

I read a tutorial on building when I was new to Second Life, and though I don't think I have the link to the tutorial saved, I am certain it was a tutorial posted by a Linden.

The tutorial advocated the practice of saving prims by using alpha textures. The exampe was a water tower with criss-crossing wooden beams. It pointed out how clever it was to build this from a couple of prims and alpha textures, rather than many prims (for each individual wooden beam.)

For whatever reason, Second Life's primary content constraint is prim count, which encourages alternatives to prim use like huge alpha textures.

Want to double the prim count? Pay a lot more tier (going from 117 prims to 234 prims is an extra $5.00 USD per month). Double (or worse) the texture size? That's free. Small textures cost the same one-time cost of L$ 10 (~ $0.03 USD).

After reading a lot of forums over a long period of time, I know now how much more of a rendering cost those alpha textures may impose over more prim use. But the limit is still based on prims.

Oh, absolutely. And they will also complain about how laggy it is while wearing 3000 prims worth of jewelery and accessories that all use 1024x1024 textures.... There is no winning this particular battle.

because to LL that's the only part they care about. Alpha texture is a performance hit to the end users client machine. Those with high end machines don't even notice. But that's all irrelevant to the LL side of things. The servers don't actually *render* anything. It's all 1's and 0's. So what do they care about alpha textures? The servers have to deal with physics. Physics involves equations per object. Not surprising LL would advocate alpha textures at all. It passes the burden off their servers and onto users machines. It's a really screwed up way of doing 3D, but it makes perfect sense for them (and them alone).