View.draw2d(GL_POINTS, pts) on ATI with AA

[thomthom]

I just came across something odd. I'd been working on a tool - using my home computer with an nVidia card. Everything working fine. Drawing a series of points on screen.
But when I tested it at work - nothing appeared. Cut a long story short, when using view.draw2d(GL_POINTS, pts) on an ATI card with AA on, the X and Y co-ords must be in the centre of the pixel.

So instead of [20, 30, 0], one must add half a pixel: [20.5, 30.5, 0] to ensure it's drawn on all cards.

My computer at work had an ATI Radeon 2X something something - latest drivers etc. Windows7 64bit. I tried with my old computer at home, Vista 32bit, ATI Radeon 9800 - older drivers - same issue.
When I turned AA off the points where drawn fine - but it's only when AA was on.

nVidia cards I tested draw the points no matter what.

Seeing how this appear ATI cards in general, not just one model or driver version - is it ATI's implementation that's bugged, or could it be something in SketchUp?

Test code:

class PointTest
  
  def onLButtonUp(flags, x, y, view)
    view.invalidate
  end
  
  def draw(view)
    t = Time.now
    32.times { |j|
      32.times { |i|
        view.draw2d(GL_POINTS, [100+i,100+j,0])     # This is not drawn with ATI and AA.
        view.draw2d(GL_POINTS, [100.5+i,200.5+j,0]) # This works in all cases.
      }
    }
    puts "Point Fill Test; #{Time.now - t}"
  end
  
  def deactivate(view)
    view.invalidate
  end
  
end # class

[dacastror]

This happens with other constants? would it happen the same with GL_QUADS or GL_LINE_LOOP?

[thomthom]

Yea, think so.