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Surface Normal (Again)

Started by Iceman May 14, 2000 at 6:55 AM 3 replies 850+ views

Original Post

May 14, 2000 at 6:55 AM

I've tried to specified the simple square plain surface normal. Can you guys tell me if I understand it right? Here's my code: glBegin(GL_QUADS); glNormal3f(-1.0f, 1.0f, 1.0f); glVertex3f(-1.0f, 1.0f, 1.0f); glNormal3f(-1.0f,- 1.0f, 1.0f); glVertex3f(-1.0f,-1.0f, 1.0f); glNormal3f( 1.0f,-1.0f, 1.0f); glVertex3f( 1.0f,-1.0f, 1.0f); glNormal3f( 1.0f, 1.0f, 1.0f); glVertex3f( 1.0f, 1.0f, 1.0f); glEnd(); Edited by - Iceman on 5/14/00 7:00:57 AM

alistair b

May 14, 2000 at 7:17 AM

The normal vector points out from the quad, so the normal
should be the same at all four vertices. (it also has a length of one unit so x*x + y*y + z*z=1)

also I don''t think you need to keep redefining the normal - they are all the same. so you could try something like:

glBegin(GL_QUADS);
glNormal3f(0.0f, 0.0f, 1.0f);
glVertex3f(-1.0f, 1.0f, 1.0f);
glVertex3f(-1.0f,-1.0f, 1.0f);
glVertex3f( 1.0f,-1.0f, 1.0f);
glVertex3f( 1.0f, 1.0f, 1.0f);
glEnd();

i hope this is right

alistair

Iceman

May 14, 2000 at 11:42 AM

OK, Thanks
But I still confuse about Surface Normal anyway.
Anybody can tell me the good source about this topic?
(I didn''t know anything about vector at all.)

alistair b

May 14, 2000 at 2:08 PM

You should look at the OpenGL Superbible for info on this type of thing. Chapter 9 Section "Using a Light Source - Surface Normals" is what you want.

It is at:

http://www.itknowledge.com/reference/archive/1571690735/ewtoc.html

alistair

Morgan

May 14, 2000 at 6:18 PM

Also, Nate (nate.scuzzy.net) has a good tutorial on normals and stuff.

Morgan

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