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  Change draw color  (Read 639 times)
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Offline nhmllr

Senior Duke


Medals: 1
Projects: 3


slow and steady...


« Posted 2013-03-31 17:16:51 »

I'm making a 3D tetris game to get used to working with OpenGL. When I draw the scene (with my draw() method) I first draw all the tetris cubes on the scene. They are textured cubes of different colors. Then after I draw these cubes, I draw "gridlines," which are lines drawn over the scene to show the "grid."

I want these lines to be drawn in white. Here is what my code looks like:
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public void draw(){
      glPushMatrix();
     
      //translate the scene
      glTranslated(-GAME_WIDTH/2 + 0.5, -GAME_DEPTH/2, -30);
     
      //draw all the tetris cubes
      for(TetrisCube tc : cubes){
         if(tc.x > -1 && tc.x < GAME_WIDTH
               && tc.y > -1 && tc.y < GAME_HEIGHT
               && tc.z > -1 && tc.z < GAME_DEPTH)
            tc.draw();
      }
     
      //set the color of the gridlines to white (doesn't work)
      glColor3f(1f, 1f, 1f);
     
      //draw all the gridlines
      for(DrawLine dl : gridLines){
         dl.draw();
      }
     
      glPopMatrix();
   }


However, the lines are not white. Instead, they are the color of the last block drawn, which might be red, blue, etc.
This is a little weird, because the guides I've read online have suggested that this would work. I probably don't understand what the glColor3f() really does, but I don't know what to use instead. How would I solve this problem? Thanks.
Offline Vladiedoo
« Reply #1 - Posted 2013-03-31 17:31:18 »

Bind a white texture after you draw all your cubes
Offline davedes
« Reply #2 - Posted 2013-03-31 17:47:55 »

Bind a white texture after you draw all your cubes
Better yet, sample a texture region of opaque white from your currently bound texture (e.g. UI/font sheet), and render both the cubes and the lines using different calls to glColor4f to change the colours. That way you only have a single texture for your whole application!

A similar concept is discussed here:
https://github.com/mattdesl/lwjgl-basics/wiki/Batching-Rectangles-and-Lines

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Offline nhmllr

Senior Duke


Medals: 1
Projects: 3


slow and steady...


« Reply #3 - Posted 2013-03-31 18:59:31 »

I'll do that for now, but is there really no other way to do it? Seems as though it should be simpler than that.

Thanks though, it does work!
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