About the principles of making trees

Hi;

I am currently looking at how to make trees in SL. I am investigating for making a video tutorial and i allready have got something that works, but i am not yet satisfied. So i hope, i can get some tips from here.

From what i learned so far, i see these basic approaches:

1.) Linden trees (which can not be created but just used from the libraries)
2.) textured trees (using crossed alpha textures)
3.) using 2.) in combination with prims and/or sculpted prims

Now i have a couple of questions about how to make a tree "look good":

1.) when i use 2 crossing flat prims, what would be a good strategy for the texturing?

shall i place a full side view of the tree on the front side and the same but mirrored view on the backside ? And shall i use 2 images of the tree which have been made at from front view and from side view of the tree (0/90 degree) ? Or is there a better way to go ? What principle strategies do you use ?

2.) How many crossed prims would you recommend to use ?

I have seen trees with just 2 crossed prims and i have seen trees with many (several tens of) crossed prims. From prim efficiency i guess the less prims are used the better it is. From looking at the results i guess the more prims are used the more complex the tree looks (not necessarily better though). Is there a reasonable "avarage" ?

3.) What resolution shall i use ?

I have been playing around with some textures and i tried to go to some extremes just to watch what happens. So i found no significant enhancement when i use high resolution textures. i tried 2048*1024 (width/height) and i compared it with 512*256 textures but could not see a big differences in the viewer. Is there some sort of automatic downsizing of the resolution happening during import of the textures ?

EDIT: I learned now, that 1024*1024 is the max texture size (beeing downsized by the viewer) So it is no good idea to use higher resolution textures here and hope, that the trees look better. It does not work like this. Hence getting higher resolution is directly coupled with using more prims. So back to question 2

4.) Alpha

Well, not much to say, but are there strategies to reduce the alpha sorting problem somehow ? Any simple trick which makes this problem less apparent ?

5.) Are there any further tipps available ?

For instance where to find good textures for tree construction ?
Other things to take care about ?
Tutorials on the web ?
Maybe some name of "tree construction experts" which i could consult and who are willing to share their knowledge?

Thanks for any information in advance
Gaia

1.) when i use 2 crossing flat prims, what would be a good strategy for the texturing?

The last trees I made, I tried using four different textures. I created my trees in a 3D app, and then imaged them from each side. This had some advantage in that the foliage from front and back actually looked like the front and back of the tree. However, if you are not looking at the tree at an angle perpendicular to the plane of one of the prims, then what you see is usually a composite of two or more of the prim faces, altered by alpha sorting. In short, trying to be "perfect" doesn't help much, and doesn't realy get the effect desired. Further, if you used four or six individual textures for that three, it takes longer to load the textures.

You could still do it, doing a "texture sheet" with 4 512 x 512 textures combined into a single 1024 x 1024, or better yet 4 256 x 256 images combined into one 512 x 512. Use offsets and repeats to pick the image you want.

You can try the texture sheeting and different textures from each face, or just one texture per panel, mirrored on the back. The latter seems standard, and most people won't notice any diference from more labor-intensive methods.

2.) How many crossed prims would you recommend to use ?

Two seems to do well for most instances, while 3 makes a more "bushy" tree that looks more the same from various angles.

3.) What resolution shall i use ?

I tend to use 256 x 256 for each image, or 128 x 256 if it is a skinny tree. I wouldn't use more than 512 x 512, unless you're doing a huge tree.

4.) Alpha

Not much you can do there. You NEED the alpha sorting glitch to make a crossed planes tree work, and can't get rid of the effect anyway. Sometimes rotating a tree slightly, so the planes of the tree and a nearby surface that they are glitching with can fix the glitch somewhat between a tree and a nearby wall. Try not to have any plane in the tree parallell to a nearby alpha-textured wall.

5.) Are there any further tipps available ?

Always leave 2 to 4 pixels of 100% alpha at ALL edges of the texture, including the bottom of the trunk. This eliminates the 'little asterisk' above the tree, which is the bleed-over, edge to edge, of the trunk base.

Keep the trunk of the tree centered on the prims, as much as possible. It will look better as you move around the tree.

Make the prims slightly flexi, but stiff. You have to flip them top for bottom to do this, so they stay still at the bottom and move at the top. Done right, they will shift a bit with the wind, like Linden trees do.

A prim trunk, non-sculpty, works well for trees with fairly straight trunks, like pines. This also allows you to get the crossed planes up above avatar height, which reduces problems when clicking near the trees or trying to maneuver your camera near the trees.

I think all the questions that you ask are only ones that you can answer, based on your objectives. As you have said, there is the full range of trees out there, from two-prim simple to 30 prim elaborate. How you approach the construction of a tree is intimately related to what you want to accomplish. And the answer to each of your individual questions depends on what type of tree you have made and the answers to the other questions. For example, if you have 10 prims in the leafy part of the tree, you can probably get buy with a lower resolution texture.

You would learn a lot more if you simply sat down and answered all of these questions yourself by making a few trees. Then you might actually have the knowledge required to make the video you referenced.

I agree, that learning by doing is a very good approach. But learning from others is not bad either, no ? I also mentioned in my secnd sentence, that i am not asking questions before doing experiments, but i rather want to know, how others do it, since i found some caveats with the different approaches while i was experimenting with different tree making aspects...

And my intention is not to show others, that i can make trees (in fact i am not a tree maker), but i want to show how trees function, what alternative construction principles do exist and what benefits/disadvantages the individual methods have... And where people should take care ...

Having said this i am still interested, how other builders make trees and if you want to share your knowledge. And i ask especially in the texture forum, because i think that most issues with trees are burried in the correct usage of the textures...

I got a "1-prim cross tree" type from Hang Loose that was a sculpted prim. The sculpt was made up of 6 crossing panels, so it looked as though 3 prims were used but it was only one. It made for a very simple sculpt map and I think the tree texture was done in repeats so they could keep the resolution high. (^_^)y

On method to reduce alpha sorting problem but only work non-flexi prims is to add a 45 degee twist to the beginning and end of the box then reduce the size to 0.01 one the Y size. (also and makes the prims larger than 10m in on direction which is the distance from opposite corners)

This image shows the old way on the left and the Twisted box version on the right. One plane was colored black so you can see the intersection of the two planes more clearly. As you can see on the right you can see the intersection of the two place. where the left looks to have the alpha sort problem.

So this is one way to get around with the alpha sort problem but you can not make them flexi with this method. Kind of surprised I have not seen more of this. Oh and for the texturing 0.5 x 1.0 on all sides then offset the sides 0.25 and -0.25

Also for fun a single prim 16 plant sculpt. The problem I have with those 1 prim 1 sculpt plant is they kill frame rate in large numbers. 1 sculpt is 2048 facets. one box is 108 facets (3 prim plant 324 facets). So nearly 6 times more geometry to render for the simple prim sculpt the imitates the 3 plane plant.

Now on the other hand the 1 prim 16 plant which imitates 32 prims is a little savings. 3456 facets vs 2048.