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# cutting planes

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hi people... what are cutting planes and how do we manipulate them in opengl? thanks for the help you can give

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Hi

I assume, since you ask about what a clip plane is, you don't know what a plane is...

Is short, a plane is a flat surface that expands in all directions indefinetly..
Right, it's actually not a surface at all...but i don't know how to explain...

For example, think of it like an axis in 2D. If you say you can't go further than 4 on the X axis it really dosn't matter what your Y position are, you still can't get over that X "border"...
Ok, obius you think. Then think of it in 3D with that same X. Now it dosn't matter where on the Y or Z axis you stand, you can't get over the X border here either...

Hope you understand this [smile]
Planes can be defined in a varity of ways, but the most common is:
1. A normal(N) and a "distance"(D).
2. A point on the plane(P) and it's normal(N).
3. 3 points, the plane is aligned with the points.

Now, what to what a clip plane is.
I imagine it can be used in quite a few ways but what comes to mind is using them to create a "view frustum", the area which a camera can see. The planes will be the "borders" of your frustum and will "clip" your scene, hence clip plane [smile]

I suggest you do a search about planes, clip planes and frustum...you might find more, AND more acurate info there [grin]

EDIT: Right, read your post a bit fast there...thought you said clip [smile] Well, a cutting plane is still a plane, AND it's no difference between a clip and a cutting plane, though their uses are different. With clip you "remove" things and with cutting planes you can, in a manner, "cut" a world into tiny pieces and only draw the pieces you can potentially see (octrees works like this).

Hmm, i hope i got it correct this time [smile]

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