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overlay in models

Started by stroma Oct 10, 2004 at 8:26 AM 5 replies 650+ views

Original Post

Oct 10, 2004 at 8:26 AM

hi, i am making a simple demo nd i want to add palm trees on terrain. soo i want to know how can i make a simple overlay effect on leafs? because i dont want to use high ply leafs, they are like billboard.... edit: i am using obj file format for trees but can be change.. edit2: are there any extension for this? thank you.. [Edited by - stroma on October 10, 2004 10:47:16 AM]

zedzeek

Oct 10, 2004 at 3:46 PM

yuor question doesnt really make sense

666_1337

Oct 11, 2004 at 2:00 AM

well, if you use models for your tree's you don't need overlay for the leafs...

stroma

Oct 11, 2004 at 8:52 AM

sorry about english, i think i did tell wrong.. here is the picture of what i want to make:

http://www.mikrop.gen.tr/stroma/palm.jpg

rick_appleton

Oct 11, 2004 at 8:59 AM

The leaves are just a few quads linked together at the edge (from what I can see in the picture, it seems to be 3 or 4 quads) and then textured using an alpha-blend operation, or an alpha-test operation.

To do this operations, your texture should have an alpha-channel and you demo should support drawing objects with alpha blending. Here's a demo from NeHe showing how alpha-blending is done.

mikeman

Oct 11, 2004 at 9:02 AM

You need alpha testing.

First,you should load the leaf textures as RGBA textures, with the alpha channel set to 1.0 for visible texels and 0.0 for "invisible".

Then enable alpha testing with glEnable(GL_ALPHA_TEST) and set glAlphaFunc(GL_GREATER,0.0) to discard fragments with alpha=0.

stroma

Oct 11, 2004 at 9:21 AM

soo i need to load tga files with alpha channels? ok, i will add tga support. but i want to learn that, can make a alpha blending with RGB colors, will it look bad?

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