Change Lightsources position...?

NeHe Productions Affiliates

Started by SnAkE June 22, 2001 09:00 AM

6 comments, last by SnAkE 22 years, 9 months ago

122

Author

June 22, 2001 09:00 AM

Hi there, I decided to use lighting for the first time, but now there is something, that I do not understand: OK, read NeHe''s tutorial on lighting, and it works quite allright, but what to do if I want the Lightsource to be part of the "world", and not of the camera?! (Get that?) In the tutorial the Light is static, so you can not move it around, and what do I have to do, to make it moveable??? Thanx, SnAkE SnAkE''s Programming Resources

SnAkE's Programming Resources

Obliviator

122

June 22, 2001 09:12 AM

just use

glLightfv( GL_LIGHT0, GL_POSITION, posLight0 );

with

float posLight[4]; // x, y, z, w

of course GL_LIGHT0 is exchangeable with GL_LIGHT1 ...

hope this helps
Johann Fuchs

quiet! don't disturb my sleep. i'm in office right now.

SnAkE

122

Author

June 22, 2001 09:29 AM

Got some code:

in the InitGL-Function, I wrote the following:

glLightfv(GL_LIGHT1, GL_AMBIENT, LightAmbient);glLightfv(GL_LIGHT1, GL_DIFFUSE, LightDiffuse);glLightfv(GL_LIGHT1, GL_POSITION,LightPosition);glEnable(GL_LIGHT1);glEnable(GL_LIGHTING);

And if I run it now, everything works fine... but the lightsource is always at a fixed position, compared to the camera.
Now I test something like that in the DrawGl-Function:

LightPosition[0]=   0.0f-move_x;LightPosition[1]=  -5.0f-move_y;LightPosition[2]= -25.0f-move_z;glLightfv(GL_LIGHT1, GL_POSITION,LightPosition);

With this code added, the scene is completely black...

Question: What do I have to do, to make the light work?

SnAkE''s Programming Resources

SnAkE's Programming Resources

Anonymous

June 22, 2001 10:05 AM

Precalculate your geometry surfaces normal coordinates and assign them with glNormal3x() - function per frame.

_DarkWIng_

602

June 23, 2001 01:47 PM

I''m also having problems with this...

I have something like:
LightPosition[0]= light1.z;
LightPosition[1]= light1.y;
LightPosition[2]= light1.z;
glLightfv(GL_LIGHT1, GL_POSITION,LightPosition);

but NOTHING happens when I move the light...
and I have normals(actualy i reied both per vertic and per face) and nothing seems to work...

There are more worlds than the one that you hold in your hand...

You should never let your fears become the boundaries of your dreams.

zedzeek

529

June 23, 2001 10:39 PM

check the faq (lighting section question 5 IIRC)
http://www.frii.com/~martz/oglfaq/
asfter u move the camera u must position the lights again.

http://members.xoom.com/myBollux

Captain Courgette, eat more veg

SirKnight

316

June 23, 2001 11:13 PM

Make sure the fourth component in the light vector is a 1.0 if you want to move the light around. Like i said in your other post and like it says in the NeHe tutorial, the 1.0 tells opengl the vector you specify is the light position. If its a 0.0 then the light is an infinate distance away and the vector you choose is the direction of the light only.

-SirKnight