Irrlicht Engine

Hello,
Now I have my tiled terrain zone system.

I would like to know the possibilities of texture editing on them, but I must not use shaders that requires a newer graphics card like GLSL or HLSL.

Do I have to edit the texture's pixels by getting it's pixels pointer ?
Or is there another easy solution ?

Thanks.

Yes, no.
This technique is called texture splatting or texture blending. Done in realtime you can come up to the "megatexture" technique.
Look at this article http://www.flipcode.com/archives/Terrai ... tion.shtml
Advice, practice outside irrlicht. When it works, grab() lock() image and access pixels to set them dirty.