Michael: Laplace is about university level mathematics. It was meant as an off topic joke Anyways, you use it to solve differential equations (if thats what they are called in english), those types of equations that are impossible to solve with “pre-university maths”. You transform the equation into simple arithmetics, solve it, and then transform it back. It might sound simple, but the transformation is a pain.
haigu: G is it’s own texture, independent of the two other landscape textures you want to blend. And the two textures CAN contain an alpha channel, but you don’t use it, so generally they are both of RGB format. G can, depending on blend function, be either GL_ALPHA, or GL_LUMINANCE (GL_INTENSITY might work aswell, never tried it though).
And because it is an independend texture, it can be a 1D texture. If you only draw G (as a 1D map) onto the landscape and using a height based ground detail (grass at lower levels, and rocks at higher levels), you can simply map the terrains altitude to the texture coordinate (normalized of course). Sorry abouth this “loose” explanation, but lets just say, for get 1D, and stick to 2D maps.
Mongoose: You can do it without extensions, but it’s not as simple as with IMO. You can solve it with alpha channels and stuff.
To all: Recieved a mail from someone who read this thread, and wanted a piece of code to do this blending. I will write a small tutorial, or just a brief explanation rather, along with some code. Will post a link to the page later, when I have written and uploaded it.