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View Full Version : what is a "normal" for?



fabianspring
08-09-2002, 09:44 AM
Hello!
So.. I am trying to learn about lightning now, and really stuck at something familiar sounding like a "normal".
Could someone please tell me what this is for and/or how to use it?

I have got a formula for this too:
AxB=(Ay*Bz-Az*By, Az*Bx-Ax*Bz, Ax*By-Ay*Bx)

It's not that I don't understand the math, but the connection with "light"...

Thank you so much guys
Fabian

Latrans
08-09-2002, 10:10 AM
Probably the simplest way to explain it is to say that a normal is a directional vector. As that direction points more towards the light, the light will affect it more. And depending on what your shininess is at, it also affects how much specular component will be applied. As the normal and light get close to pointing directly at each other, there will be more specular light applied.

Miguel_dup1
08-09-2002, 12:36 PM
All vectors are directional latrans... http://www.opengl.org/discussion_boards/ubb/smile.gif

A normal is a bit of a weird term sometimes...

A normal is a unit vector. A Unit vector has length 1. And this normal vector is orthogonal (90 degrees) to the original vector...
Orthogonal is just a fancy way of saying perpendicular...

Now, I say that it is a bit weird because a normal vector is more commonly known in mathematics as an orthogonal vector... When this vector is of length 1, you call it orthonormal.
So, a more correct way to call a normal vector is orthonormal...

Latrans briefly explained how it works in lighting...
Imagine a surface... When you have a light shinning off of it, you will see that at a 90 degree angle on the surface you will get the brightest lighting effect. So, this normal vector gives the highest lighting possible, and when the angle of coincidence of the light source changes, your lighting will change accordignly, and the normal vector will help you kow how much lighting to produce....
A bit confusing, but you can let OGL do the work for you...