Home/ Questions/Q 7066289
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-28T05:03:54+00:00

My java application uses jogl to create surfaces with an overlaid grid. The lines

  • 0

My java application uses jogl to create surfaces with an overlaid grid. The lines of the grid are anti-aliased. However, on Windows the anti-aliasing is complete garbage, unless I add a small alpha value to the surface. Here are screen shots of the same scene on all three platforms:

Mac OS X:

Mac OSX

Ubuntu 11.10:

Ubuntu 11.10

Windows 7:

Windows

Windows 7 with alpha=0.01:

Windows with (small) alpha (0.01)

The basic procedure to create this is as follows:

gl.glPushAttrib( GL.GL_ALL_ATTRIB_BITS );
gl.glEnable(GL.GL_POLYGON_OFFSET_FILL);
gl.glPolygonOffset(1.0f, 1.0f); 
drawSurface(gl);
gl.glDisable(GL.GL_POLYGON_OFFSET_FILL);
gl.glPopAttrib();

gl.glDisable( GL.GL_LIGHTING );
gl.glDepthFunc(GL.GL_LEQUAL);
float[] c = {0, 0, 0, 0.5f};
gl.glColor4fv(c, 0);//the alpha here gets overridden if one is specified for the surface (which is why the Windows-with-alpha produces a darker grid)
drawGrid(gl);
gl.glDepthFunc(GL.GL_LESS);
gl.glEnable( GL.GL_LIGHTING );

The drawSurface() method also does the following before creating the polygons for the surface (using GL_TRIANGLE_STRIP primitives):

gl.glPushAttrib(GL.GL_LIGHTING_BIT);
gl.glColorMaterial(GL.GL_FRONT_AND_BACK, GL.GL_AMBIENT_AND_DIFFUSE);
gl.glEnable(GL.GL_COLOR_MATERIAL);

The drawGrid() method sets up anti-aliasing like so:

gl.glEnable(GL.GL_BLEND);
gl.glBlendFunc(GL.GL_SRC_ALPHA, GL.GL_ONE_MINUS_SRC_ALPHA);
gl.glEnable(GL.GL_LINE_SMOOTH);
gl.glHint(GL.GL_LINE_SMOOTH_HINT, GL.GL_NICEST);

The grid itself is created using GL_LINE_STRIPs

I’ve read up on the OpenGL documentation regarding line anti-aliasing and also tried out the polygon offset example here.

As for hardware, I have dual boot IBM ThinkPad (64-bit quad core) with an integrated nVidia 3100M card and an Intel Core 2 Duo iMac which has an ATI Radeon. Since Ubuntu and Windows are running on the same hardware, I know it can’t be a hardware issue.

I’m looking for suggestions for improving the anti-aliasing of the grid lines on Windows.

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    Turns out I had not tried (I thought I had, but I did not rebuild and test it correctly)
    gl.glDepthMask( false );

    Adding that in correctly did greatly improve the fragmentation of the anti-aliased lines of the grid.

    That said, I’m still not 100% happy with the look of the lines, but, for now, this question is resolved. Here is a screen shot of the ‘improved’ grid lines:

    enter image description here

    While this is a great improvement, it’s still not as good as Mac OS X or even Ubuntu.

    • 0