How to paint 2D Interface over 3D render

SkyNet800 · by **SkyNet800** » Wed Apr 01, 2009 5:08 pm

Hello.

I´m making a 3D Game (rally game ;D) .

At this time, I´m trying to paint a 2D Interface over a 3D rendered scene, but when I try to create the Cavas, using "mySurfaceHolder.lockCanvas", this method returns null. It´s like if Opengl locks surface and I can´t access to it.

Does anybody knows how can I do that?

B_Thax · by **B_Thax** » Tue Apr 07, 2009 1:03 pm

Normally a 2D surface in OpenGL or Direct X is just a plane drawn after all your 3D work is done. Also OpenGL can priorities some pixels against others using the same depth-value. Have a look at Nehe OpenGL (http://nehe.gamedev.net/) to see how he did it.

If I find some code I'm using to render a 2D scene I'll post it.

SkyNet800 · by **SkyNet800** » Wed Apr 15, 2009 11:30 am

At last,i´ve done it by texturizing 3D TRIANGLES, but using some modifications:

First I take real screen size by this function located at Surface class:

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Using java Syntax Highlighting

onSizeChanged(int w, int h, int oldw, int oldh) 
 
   {
 
        if(w != 0 && h != 0)
 
        {
 
                screenW = w;
 
                screenH = h;
 
        }
 
  }
 
Parsed in 0.039 seconds,  using GeSHi 1.0.8.4

Then, once painted all 3D game, I can paint 2D INTERFACE setting up GL10:

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Using java Syntax Highlighting

// Reset projection matrix:
 
   gl.glMatrixMode (GL10.GL_PROJECTION);
 
   gl.glLoadIdentity ();
 
   // Then change render type to orthogonal to prevent perspective using real screen size  (1 pixel = 1 unit)
 
   gl.glOrthof (0f, screenW, screenH, 0f, 0f,1f);
 
   // Reset modelview
 
   gl.glMatrixMode (GL10.GL_MODELVIEW);
 
   gl.glLoadIdentity ();
 
   // And at last, I eliminate DEPH TEST to prevent triangle ordering
 
   gl.glDisable(GL10.GL_DEPTH_TEST);
Parsed in 0.037 seconds,  using GeSHi 1.0.8.4

Now I can paint all 3D elements:

All elements have to had its own triangles to be texturized, but this triangles should be defined in 2D:

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Using java Syntax Highlighting

// Points coords:
 
   float[] coords = 
 
   {
 
       // X, Y
 
      20            ,         10,
 
      20                ,          0,
 
        0               ,          0, 
 
        0               ,        10
 
  };
 
   //Texture coords
 
   float[] texturCoords = new float[] 
 
   { 
 
                1f      ,         1f,
 
                1f      ,  0.005f,
 
          0.005f        ,  0.005f,
 
          0.005f        ,     1f
 
   };
 
   // Triangle Strip definition:
 
   float[] vertex_strip = {1,0,2,3};
Parsed in 0.047 seconds,  using GeSHi 1.0.8.4

then you should create buffers (coordsBuffer,textureBuffer,triangleStripBuffer), and then you can call all paint functions.

This is an example to paint only a 2D image texturized BUT USING "real pixel" size.

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Using java Syntax Highlighting

gl.glActiveTexture  (GL10.GL_TEXTURE0);
 
   gl.glBindTexture     (GL10.GL_TEXTURE_2D, textureIndex);
 
   gl.glFrontFace               (GL10.GL_CW);
 
   gl.glPushMatrix();
 
   //  Place element:
 
   gl.glTranslatef              (x, y, 0); // X and Y are real pixel coords
 
   // Set VERTEX buffer (see that we specify 2 coords per element instead 3 because we have defined coords as 2 elements
 
   gl.glVertexPointer   (2, GL10.GL_FLOAT, 0, coordsBuffer);
 
   gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0,  textureBuffer );
 
   gl.glDrawElements    (GL10.GL_TRIANGLE_STRIP, vertex_strip.length, GL10.GL_UNSIGNED_SHORT, triangleStripBuffer);
 
   gl.glPopMatrix();
Parsed in 0.071 seconds,  using GeSHi 1.0.8.4

Thats all.

How to paint 2D Interface over 3D render

How to paint 2D Interface over 3D render

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