I have two textures like below:
the first one(a 7*19 texture with a triangle inside):
the second one(a 7*19 texture with a polygon inside):
I am gonna map these two textures into framebuffer. And I will
dedicate the blue color to the first one and red color to the second
one. So I have to use the GL_MODULATE so that I can use the glcolor3f
to decide the color of texture before the scan-conversion(Inside
texture buffer, these two textures are just black(0)&white(1)).
Here is what I want. In the overlap area, if texture1 is black and texture2 is black, the last color should be black. In the place that one of the texture is not black, another one is black, the last value remains as the nonblack value. And if both texture1 and texture2 have nonblack color, the upper one defines the last color.
The combination of "GL_ONE,GL_ONE_MINUS_SRC_ALPHA " is not working. I tried other combinations, no one works.
I think maybe the simple blending function can’t solve this problem. Maybe something in the glextension set can do the work.
Any help is appreciated, thanks