RE: [gl4java-usergroup] lighting problem

[Combe, C. <C....@na...>]

thanks,
col

-----Original Message-----
From: Antony Ribot [mailto:an...@li...]
Sent: 09 July 2002 16:18
To: Combe, Colin; gl4...@li...
Subject: Re: [gl4java-usergroup] lighting problem


http://www.acm.org/pubs/tog/GraphicsGems/gemsiii/newell.c

Antony

----- Original Message -----
From: "Combe, Colin" <C....@na...>
To: <gl4...@li...>
Sent: Tuesday, July 09, 2002 3:59 PM
Subject: RE: [gl4java-usergroup] lighting problem


Thanks Jens and Antony,

yes, as you have both pointed out i have a problem with my normal
calculations - a simple cube works fine. Oh dear... i'm not sure how to
start debugging...
cheers,
col

-----Original Message-----
From: Jens G=FCnther [mailto:jen...@ag...]
Sent: 09 July 2002 15:30
To: Combe, Colin
Subject: Re: [gl4java-usergroup] lighting problem


Hi Colin,

i use the following structure in my display()-method:

glMatrixMode( GL_PROJECTION );       // define properties for =
projection
glLoadIdentity();                    // initialize projection matrix
glFrustum();                         // define view frustum, you can
                                      // also use gluPerspective(...)
glMatrixMode( GL_MODELVIEW );        // start of model transformations
glLoadIdentity();                    // init modelview-matrix
// place here objects, which are static to the cameraposition. This
// means that all objects you draw here move with the camera, like a
// headlight.
glLoadIdentity();                    // again init modelview-matrix to
                                      // forgot the transformations =
make
                                      // to the camera-static objects
// now place here your transformation for the camera.
gluLookAt(...);
// and now after a long way of initializing... draw your objects, also
// lights like the following ( in my code ):
glLightfv( GL_LIGHT0, GL_POSITION, vpos ); // static Light
glPushMatrix;                        // save current transformation,
                                      // the cameraview
//transform object
//draw object
glPopMatrix;                         // forgot last transformations

hope, this would help you. The logic for translations, rotations and
scale is'nt easy to understand, i had tried many times to get the right
orders.
Finally i compiled your code and run it. If you exactly observe your
model you must recognize that it seems as the light will rotate faster
as the model, so I THINK YOU HAVE SOME PROBLEMS WITH YOUR NORMALS!
Because if you comment out the push and pop between the lightposition =
is
made then you will have a structure nearly to my.

good luck ;)
Jens


-----------------------------------------------------
                   [ age-works  softwaretechnologies ]

                             http://www.age-works.de


  Jens G=FCnther

  email:                  jen...@ag...
-----------------------------------------------------



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