opengl: moving the light with level

This is a discussion on opengl: moving the light with level within the Game Programming forums, part of the General Programming Boards category; k, how do you get the light to move with the level? simple question, im sure you know what im ...

  1. #1
    Flash Animator, OF DOOOOM bluehead's Avatar
    Join Date
    Nov 2001
    Posts
    269

    opengl: moving the light with level

    k, how do you get the light to move with the level? simple question, im sure you know what im talking about
    Code:
    #if _emo
      #define stereo_type_i_dislike
    #endif

  2. #2
    Crazy Fool Perspective's Avatar
    Join Date
    Jan 2003
    Location
    Canada
    Posts
    2,640
    set the position everytime the viewpoint changes. (ie: put this in your render loop)

    glLightfv(GL_LIGHT0, GL_POSITION, lightPosition);

  3. #3
    Software Developer jverkoey's Avatar
    Join Date
    Feb 2003
    Location
    University of Waterloo
    Posts
    1,903
    To Bluehead's sig: yes I do, fluently.

  4. #4
    Flash Animator, OF DOOOOM bluehead's Avatar
    Join Date
    Nov 2001
    Posts
    269
    To Jverkoey: ha. i dont

    now, back on topic..

    i know i did it completely wrong, i took a really random guess...

    Code:
    	glTranslatef(-xmov,ymov,zmov);
    	
    	GLfloat LightPosition[]= { xmov, ymov, -zmov, 1.0f };
    
    	glLightfv(GL_LIGHT1, GL_POSITION, LightPosition);
    how do you actually update the light's position?
    Code:
    #if _emo
      #define stereo_type_i_dislike
    #endif

  5. #5
    Crazy Fool Perspective's Avatar
    Join Date
    Jan 2003
    Location
    Canada
    Posts
    2,640
    edit: hold up, im not so sure i understand the question anymore. Can you explain what your trying to do?

  6. #6
    Super Moderator VirtualAce's Avatar
    Join Date
    Aug 2001
    Posts
    9,586
    Looks like he is moving a light inside of his level. I personally don't recommend this type of dynamic lighting because the overhead is huge. This effect is usually only needed when the source of the light originates at the player or camera position. Normally this is simulating the player holding a flashlight of some type.

    Other than that, it's just a waste of GPU.

  7. #7
    Registered User
    Join Date
    Mar 2003
    Posts
    580
    He didn't ask about the validity of dynamic lighting and I always thought vertex lighting was fast enough to be trivial.

    how do you actually update the light's position?
    Well how do you update the variables you send to glLight*? Perhaps you should just call glLight3f instead of glLight3fv.

    edit:
    erm, my bad, glLight3f isn't a function, it's just glLightf
    Last edited by Darkness; 04-04-2005 at 04:31 PM.
    See you in 13

  8. #8
    Flash Animator, OF DOOOOM bluehead's Avatar
    Join Date
    Nov 2001
    Posts
    269
    Well, this "Camera" had to be made by moving the whole entire level opposite from the user's input

    and, when i just put in a light, it stays there. so the 'level' is moving around hte light
    Code:
    #if _emo
      #define stereo_type_i_dislike
    #endif

  9. #9
    Registered User
    Join Date
    Mar 2003
    Posts
    580
    So you are telling me a few things:

    -You are moving the world around the camera to simulate looking around
    -The light's position is supposed to remain in the same spot, relative to the rest of the world

    So, for every vertex of the world, you are applying a transformation to it so that it looks like you are looking around. How do you do the same to the light's position?

    edit:
    to quote something from the link I posted (go down to params, and then the GL_POSITION part of it):

    The position is transformed by the modelview matrix when glLight is called (just as if it were a point), and it is stored in eye coordinates. If the w component of the position is 0.0, the light is treated as a directional source. Diffuse and specular lighting calculations take the lights direction, but not its actual position, into account, and attenuation is disabled. Otherwise, diffuse and specular lighting calculations are based on the actual location of the light in eye coordinates, and attenuation is enabled. The default position is (0,0,1,0); thus, the default light source is directional, parallel to, and in the direction of the z axis.
    Last edited by Darkness; 04-04-2005 at 07:21 PM.
    See you in 13

  10. #10
    Flash Animator, OF DOOOOM bluehead's Avatar
    Join Date
    Nov 2001
    Posts
    269
    You guys make it sound like i'm doing it in some alienated way

    is there an actual way to move the CAMERA, instead of the whole world?
    Code:
    #if _emo
      #define stereo_type_i_dislike
    #endif

  11. #11
    Software Developer jverkoey's Avatar
    Join Date
    Feb 2003
    Location
    University of Waterloo
    Posts
    1,903
    Have a series of glTranslatef and glRotatef functions or use gluLookAt at the beginning of your code, and then use a series of glPushMatrix(); and glPopMatrix(); to render your objects.

  12. #12
    Registered User
    Join Date
    Mar 2003
    Posts
    580
    Quote Originally Posted by bluehead
    You guys make it sound like i'm doing it in some alienated way

    is there an actual way to move the CAMERA, instead of the whole world?
    No, but you can trick yourself into believing you are by using gluLookAt. But ultimately you are moving the world around a fixed eyepoint.
    Last edited by Darkness; 04-05-2005 at 06:10 AM.
    See you in 13

  13. #13
    Super Moderator VirtualAce's Avatar
    Join Date
    Aug 2001
    Posts
    9,586
    He didn't ask about the validity of dynamic lighting and I always thought vertex lighting was fast enough to be trivial.
    Lighting is never trivial. Even dot3 lighting incurs 3 muls for every computation of the dot product. On the GPU this is not a big deal, but within GL or DX it is. Most cards have a max number of lights because the computations are squared per light added to the world. Many games accomplish lighting with 1 or 2 dynamic actual lights and the rest are light-mapped textures or other texture tricks that simulate light. Most of the light in games is static, not dynamic

    is there an actual way to move the CAMERA, instead of the whole world?
    You are thinking about things in the wrong way. When you drive down the road, what does the outside scenery do and the road do in relation to your car?? It moves towards you right? So when you look at your dashboard, your gearshifter, the seats, etc., they are all seemingly motionless- even though you know they are moving. But from the car's point of view, and from yours, the world is moving, not the car.

    It's the same in 3D graphics. You must move the world relative to the camera. Essentially what you are doing is saying ok the camera is at x,y,z - so let's make x,y,z the center of the world or the origin of it. So you translate everything relative to the origin which essentially places the camera at 0,0,0 in the world. In fact, it is always at 0,0,0 and this makes the calculations much easier since everything is relative to the camera.

    In 3D graphics you must 'bring the world to the viewer or camera' instead of actually move the camera. Notice that you still do actually change the coordinates of the camera.

    Camera.Pos+=Camera.LookVector*Camera.Speed;

    But then also notice that you translate by the opposite amount which brings the camera again to the center of the world and brings all the world coordinates of all objects into camera space where everything is relative to the camera.

    This makes z depth and z ordering much simpler because we always know that the camera is the center of the world. So an object with a z value of 100 is 100 world units away from the camera, no matter what the actual world camera position may be.

  14. #14
    Registered User
    Join Date
    Mar 2003
    Posts
    580
    Lighting is never trivial. Even dot3 lighting incurs 3 muls for every computation of the dot product. On the GPU this is not a big deal, but within GL or DX it is. Most cards have a max number of lights because the computations are squared per light added to the world. Many games accomplish lighting with 1 or 2 dynamic actual lights and the rest are light-mapped textures or other texture tricks that simulate light. Most of the light in games is static, not dynamic
    *slaps forehead* didn't your mom ever tell you not to worry about speed until you've got a working implementation?
    See you in 13

  15. #15
    Crazy Fool Perspective's Avatar
    Join Date
    Jan 2003
    Location
    Canada
    Posts
    2,640
    >>*slaps forehead* didn't your mom ever tell you not to worry about speed until you've got a working implementation?

    why?? so you can have a working implementation with poor performance and realize "Crap, i designed this wrong from the start. Now i need to start over from scratch"

    The "Code now, optimize later" approach just doesnt cut it IMHO, you need to carefully consider design decisions before implementing anything.

Page 1 of 2 12 LastLast
Popular pages Recent additions subscribe to a feed

Similar Threads

  1. Critique my lighting model.
    By psychopath in forum Game Programming
    Replies: 4
    Last Post: 08-12-2006, 06:23 PM
  2. OpenGL Window
    By Morgul in forum Game Programming
    Replies: 1
    Last Post: 05-15-2005, 12:34 PM
  3. geometry won't display!?
    By psychopath in forum Game Programming
    Replies: 17
    Last Post: 09-21-2004, 10:10 AM
  4. OpenGL .dll vs video card dll
    By Silvercord in forum Game Programming
    Replies: 14
    Last Post: 02-12-2003, 06:57 PM
  5. MISC questions about OpenGL
    By Silvercord in forum Game Programming
    Replies: 12
    Last Post: 01-25-2003, 03:20 PM

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21