That sort of thing did not happen on my Radeon 9550. It does on this particular gfx card tough. Any ideas why and how can I fix it (tough I probably can't and I'll have to harass Flad to take a look at it)? I know it's been asked dozens of times, but I don't recall it ever being fixed.

And yes, I'm using the latest snapshot.

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Are you using blending? Does this occur if using an ADDITIVE_BLEND mode?

Yes, I'm using blending, but not on this screenshot (shadows are disabled, so no blending is actually done). It occurs anyway tough, shadows on or off.

If you look at those lines with a paint program you will see that they are not perfectly black, but instead about half brightness. That suggests that it's a blending issue with the two triangles. Can you turn on additive blending for those floor tiles and check if that helps?

You could try turning off the anti-aliasing.

Try calling 'glDisable(GL_POLYGON_SMOOTH)'.
It does this sort of thing on my card too and is of no use for rectangles anyway.

Yeah, it fixed it, but with the shadows and lights on, everything else looks rather BAD. I didn't have any problems on my Radeon 9550 tough, is there any way to fix it without rewriting the code? I don't want to spend another week trying to figure out a good blender combination

EDIT: I'll try.

EDIT2: Ah, thanks a lot, glDisable(GL_POLYGON_SMOOTH) fixed everything. Thanks again.

Would glDisable(GL_POLYGON_SMOOTH) have any negative effects (apart from removing anti-aliasing on untextured polygons when you might want it?)

I.e. should this be added to the OpenLayer setup code?

Well, it makes the polygon edges not to appear anti-aliased.

What I am concerned with is that this problem will affect all OpenLayer programs that use blitting operations on a GeForce FX 5600XT.

So, would it be better to disable the smoothing to avoid the problem on this card?

I think turning it off by default would be ok, as long as it's clearly stated somewhere (for those of us who are not so proficient at OpenGL) that you can use something like that to smooth the polygons. After all, I didn't even know such an option existed before today

It would also benefit people with gfx cards like mine, because I don't think many people using OpenLayer turn that particular option off.

OTOH, my Snake clone runs perfectly fine on this video card, tough it might be becase I use one large bitmap for the background and additive blending (which fixes the problem as well) for the snake and bonuses.

Polygon smoothing is disabled by default. You had to explicitly turn it on... so just don't do that

Polygon smoothing is just the wrong option for antialiasing. It just doesn't work. It's great if what you want is smoothing though, but you do need to keep in mind that your edges will "bleed" into adjacent polygons when you do that.

I had this problem too with a GeForce Go 6200.

With the polygon smoothing off you jts have to keep in mind that your Shapes will be aliased (eg. Circles).
That's why I only use Bitmaps in my game an no shapes.

Or you can turn on multisampling, which does actually work for edge anti-aliasing.

SetupProgram(MOUSE | KEYBOARD | TIMER);
else { SetupProgram(MOUSE | KEYBOARD); }
SetupScreen(sW, sH, sF, desktop_color_depth());

srand(time(0));

Game = true;

I don't see how any of these lines "explicitly turn on" GL_POLYGON_SMOOTH.

You don't see it because OL enable it by default (it's the antialiasing function).

The polygon smoothing line is located in Settings.cpp of the OL lib.
Just comment it and you will be fine.

void Settings::
SetAntialiasing( bool turnedOn ) {
   useAntiAlias = turnedOn;
   if( useAntiAlias ) {
      glEnable( GL_LINE_SMOOTH );
      glEnable( GL_POINT_SMOOTH );
      // comment this because of a GeForce bug
      //glEnable( GL_POLYGON_SMOOTH );
   }
   else {
      glDisable( GL_LINE_SMOOTH );
      glDisable( GL_POINT_SMOOTH );
      glDisable( GL_POLYGON_SMOOTH );
   }
}

Rebuild the lib afterwards.

I take offense. This is not a GeForce bug. GeForce is 100% OpenGL compliant here.

Bob, how come this effect is not visible on other GeForce cards?

I was referring to this:

Yes and I was explaining why you have not activated it yourself, it's just that OL does it for you behind the scene

Bob, no offense. Maybe it's the way it's supposed to look with that OpenGL feature, but from an end user point of view it just looks wrong.

That was his point.

It is. Really, try it. Polygon smoothing + blending / alpha testing = teh loss.

Polygon smoothing basically draws lines with attenuated alpha around the edges of the polygon, on the outside of it. That looks great if you never use blending, have one polygon by itself over some background, or are drawing only lines.

Otherwise, you see a "seam" between polygons, which is really one polygon bleeding and overlapping onto the next. That's because connected smoothed polygons don't tightly fit (by design); they overlap.

I see. Thanks for explaining it clearly.

I was also seeing this issue, on a GeForce 7900GT, and commenting out glEnable(GL_POLYGON_SMOOTH) worked. That line should be removed from OpenLayer entirely, otherwise OL games are going to look horrible on a lot cards. Besides, on other cards I don't see any real difference after removing that line.

I guess you're right. After all the polygon smoothing isn't that important at all.

Um, this might thicken the plot or I might be talking rubbish but...

When I was getting GuiChan to work with OpenLayer and I used the precompiled MSVC8 binary from Neil Walkers site there was no problem (except for clipping not working - unrelated). However when I recompiled the latest OpenLayer snapshot for MSVC8 and used it I did get the lines talked about here (clipping worked fine BTW). Unfortunately since then I decided to not use GuiChan amd formatted my machine taking with it the compiled OpenLayer snapshot so I can't verify this properly. This is on the same computer too.

Again, possibly rubbish but...

Why are you using polygons instead of quads for tiles? Quads seem like the natural choice here.

Quads are polygons, at least in this case.

I am using quads.