texture mapping of two planes

[ZbuffeR]

Ah so your image have no proper alpha ?
This is a problem you have to fix, and keep the blendfunc to the one I proposed.
Maybe just doing glColor4f(1.0,1.0,1.0,0.5) to make stuff uniformly half-transparent.

Can you show does this do exactly :
SetAlphaMatch(TRUE, 0.1, 0.1, 0.1);

Is that an exact match ? Or that any texel darker than this will be transparent ?

[jenny_wui]

Hi, I hv used the following:

glColor4f(1.0,1.0,1.0,0.5);
glEnable(GL_BLEND);
glBlendFunc( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

It works, but looks a bit dark. I could not manage to work with the following function:
SetAlphaMatch(TRUE, 0.1, 0.1, 0.1);

I think it is supposed to control the alpha of a particular texture.

As my first plane deforms and penetrates the second plane, there appears another blending. I don't want it happen. How can that be done?

[ZbuffeR]

OpenGL Blending is order-dependent.
Be sure to draw back to front, otherwise it does not work. The depth buffer works only for opaque rendering, translucent surfaces need more complex structures, search for "order-independent transparency".

It seems you are at a dead-end, can you explain the high level concept being your needs, maybe there are better solutions ?

[jenny_wui]

Actually now what I want is:
when the front plane is pressed and crosses the back plane, the colored box will not appear. Can that be done? What would be condition for this kind of blending?

[jenny_wui]

Hello, I have some simple questions about texture. How can I understand whether my texture has alpha value or not? How can I separate color of a texture for different points as I need to differentiate white portion of the texture from other portions? Questions may be too simple but I really do need to clarify these things.

[Alfonse Reinheart]

How can I understand whether my texture has alpha value or not?

You gave the texture data to OpenGL, didn't you? You told OpenGL what image format to use, yes? If you don't ask for alpha, you don't get alpha.

[jenny_wui]

Ok, I understand. I need to add alpha to have some transparency effect. But how can I separate RGB values of a certain point of texture?