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Index › Programming Questions & Help › OpenGL and 3D Libraries › 2D drawing on a 3D scene
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2D drawing on a 3D scene (Read 2017 times)
blue_veek
2D drawing on a 3D scene
Sep 11th, 2008, 10:37am  
(first post)

hello everyone!
I'm just going to be straight-forward and give an example: let's say i have a 3D scene with geometry, lights etc. and a camera that is constantly changing via user input (e.g. keyboard keys w, a, s, d and mouse).. yup, you guessed it probably, it's a first person camera Smiley what I'd like to know is an effective way to draw a HUD during the game play. what i am doing now is get the camera's position and rotation along it's center and then do some push/pop and translate/rotate to draw the text, images etc. (the magical HUD) let's say 500 pixels away from the camera and in front of it all the time. this gives the impression of a 2D overlay on the screen, but this is not so professional to do, I know.

I'm sure it's possible to do it some other way, and I'd appreciate the help.
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a computer programmer only needs chocolate, cola, and vitamin D
 
V
Re: 2D drawing on a 3D scene
Reply #1 - Sep 11th, 2008, 12:34pm  
you can use ortho mode and define a different viewport where you draw your HUD

here's a class i use to draw a fullscreen quad. it defines a space of the size of the screen and from there u just draw normally (in other words as you would normally when u using a processing sketch)

i use direct opengl calls, but you could change it easily to use processing ones.



class Overlay
{
 Overlay( GL gl )
 {
   _gl = gl;
 }
 
 void setOrtho()
 {
   //
   // save old MVP matrices and set ortho mode for screen size (pixels)
   // warning. after drawing you must call unsetOrtho() call
   //

   // Setting orthographic projection.  
   _gl.glMatrixMode( GL.GL_PROJECTION );
   _gl.glPushMatrix();    
   _gl.glLoadIdentity();
   _gl.glOrtho( 0.0, width, 0.0, height, -1.0, 1.0 );
   _gl.glMatrixMode( GL.GL_MODELVIEW );
   _gl.glPushMatrix();    
   _gl.glLoadIdentity();
 }
 
 void unsetOrtho()
 {
   // restore old matrices MVP
   _gl.glMatrixMode( GL.GL_PROJECTION );
   _gl.glPopMatrix();  
   _gl.glMatrixMode( GL.GL_MODELVIEW );
   _gl.glPopMatrix();      
 }
 
 void draw( int texID )
 {
   // bind texture
   _gl.glBindTexture( GL.GL_TEXTURE_2D, texID );
   
   gl._gl.glBegin( GL.GL_QUADS );
   
   gl._gl.glNormal3f( 0.0f, 0.0f, 1.0f );
   gl._gl.glColor4f( gl._r, gl._g, gl._b, gl._a );
   
   gl._gl.glTexCoord2f( 0.0, 0.0 );
   gl._gl.glVertex2f( 0.0, 0.0 );

   gl._gl.glTexCoord2f( 1.0, 0.0 );
   gl._gl.glVertex2f( width, 0.0 );

   gl._gl.glTexCoord2f( 1.0, 1.0 );
   gl._gl.glVertex2f( width, height );

   gl._gl.glTexCoord2f( 0.0, 1.0 );
   gl._gl.glVertex2f( 0.0, height );
   gl._gl.glEnd();
   
   // unbind texture
   //_gl.glBindTexture( GL.GL_TEXTURE_2D, 0 );
 }
 
 //
 // Members
 //
 GL _gl;
};
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Victor Martins | www.pixelnerve.com/v
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blue_veek
Re: 2D drawing on a 3D scene
Reply #2 - Sep 11th, 2008, 1:03pm  
thank you very much! this sure is better than my n00b solution.
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a computer programmer only needs chocolate, cola, and vitamin D
 
blue_veek
Re: 2D drawing on a 3D scene
Reply #3 - Sep 11th, 2008, 3:30pm  
just another thing, i can't figure out how i can use p5 functions like text("bla", x, y) with the class.. could you please, please give me an example? (i feel totally stupid)
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a computer programmer only needs chocolate, cola, and vitamin D
 
blue_veek
Re: 2D drawing on a 3D scene
Reply #4 - Sep 12th, 2008, 11:56am  
escaped from the bounds of not thinking and figured it out during the night Smiley
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a computer programmer only needs chocolate, cola, and vitamin D
 
pelintra
Re: 2D drawing on a 3D scene
Reply #5 - Sep 18th, 2008, 12:50pm  
hi, well you already got this working but something else you could make (probably slightly slower but alot simpler) e just call camera(); this will reset your viewport to its original settings and you can just draw your text after that.
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blue_veek
Re: 2D drawing on a 3D scene
Reply #6 - Sep 19th, 2008, 3:09pm  
pelintra wrote on Sep 18th, 2008, 12:50pm:
hi, well you already got this working but something else you could make (probably slightly slower but alot simpler) e just call camera(); this will reset your viewport to its original settings and you can just draw your text after that.


oh, lol Smiley
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a computer programmer only needs chocolate, cola, and vitamin D
 
starfeuri
Re: 2D drawing on a 3D scene
Reply #7 - Nov 1st, 2008, 11:59pm  
<3  This is just what I was looking for.

<3

Except!

_gl.glOrtho(0.0, width, 0.0, height, -1.0, 1.0);

Gives some strange results.


glOrtho(left, right, BOTTOM, TOP, nearVal, farVal);

so instead of

_gl.glOrtho(0.0, width, 0.0, height, -1.0, 1.0);

We want

_gl.glOrtho(0.0, width, height, 0.0, -1.0, 1.0);

Or everything is upside down and unhappy.

Thank you so much crmx!  You saved my brain!
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Processing makes me feel like I can program...
starfeuri  
kiza
Re: 2D drawing on a 3D scene
Reply #8 - Jan 3rd, 2009, 7:43pm  
Hey,
Isn't there a way to push the projection matrix before calling the perspective etc.. functions using the gl object and popping it before drawing a 2d gui?
Wouldn't it be faster then setting it back to ortho?
I tried it like this

 gl = pgl.beginGL();
 gl.glMatrixMode( GL.GL_PROJECTION );
 gl.glPushMatrix();    
 gl.glMatrixMode( GL.GL_MODELVIEW );
 gl.glPushMatrix();  
 cam.feed() // using Damkjer's Camera class..
 box(340);
 gl.glMatrixMode( GL.GL_PROJECTION );
 gl.glPopMatrix();  
 gl.glMatrixMode( GL.GL_MODELVIEW );  
 gl.glPopMatrix();
 pgl.endGL();
 text("HELLO", 100, 100);
.. but it doesn't work..
Are the two methods above mentioned the only solution? pelintra how much of a slow down is calling camera()?
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