Question about trees (transparent textures)

[typewriter]

I implimented some standard trees with the 2 perpendicular quads, using a transparent PNG for the tree texture.

Now, the tree in the foreground correctly shows the transparency through to the skybox, but obscures the other trees like a "cloak of invisibility". But it only does this when viewing the trees from *one direction*, not the other.

The trees are all part of the big "world" object. I am using glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA). Face culling is off.

I must be missing something regarding transparent texturing.. this effect is kinda cool but not the simple thing I'm doing after! Any ideas?

[Rosario Leonardi]

When you draw transparent object you have to order them back to front to have a correct behavior.

[typewriter]

A ha. I was afraid that might be the case.

But, what about the fact that a tree can also obscure itself? How would I depth sort the 2 quads which make the tree? Their centroids would be equal.

[ZbuffeR]

You can mitigate zbuffer problems by doing alpha testing on top of blending, at a low threshold.
Or use coverage alpha with multisampling.

[typewriter]

Yes, alpha test will work just fine for my purposes. Thanks for mentioning it.