I want started rebuilding some tree models based on this tutorial, simply because of the fact that it offered the opportunity to do more with less so to speak, but only last night I  saw this

As you can see you end up with a nice full tree for very few polygons. The only real downside is that there is a lot of overdraw for realtime applications. Hope this helps some folks.

so then, what is overdraw..... especially relative to this tut

overdraw is where opengl replaces the color of a pixel more than once per frame.  For example, if you draw a box that is far away, and then draw a box closer to you that blocks your view of the other box, you'll have done more work than if you draw the front most one and then the back one because opengl will (assuming the correct zstate) be able to determine that it doesn't need to draw what it can't see.

thanks, Is there any thing I can do do to minimize it . that tut seems the best approach to archiving  a "lush jungle canopy" type effect.

The RenderQueue does a lot of the work for you if you use it.

Regarding the overdraw problem from the paper. Because the tree is made up of a high collection of polys that overlap with the tree texture and have alpha transparency, the overdraw is going to be worse (alpha blending for each overlapping quad).

right, and if you are doing alpha blended quads, there's not much choice to be had.

thank for all the info very useful, I have a few Ideas for minimizing overlap I'll see if it works

thanks again