MAMEWorld Forums - EmuChat - Re: I was playing around with the new MAME screen settings.

> I feel obligated, as the pretentious CRT guy, to present some possibly useless
> information.

I see no useless information. All true what you wrote.

> CRT screens come in three basic shapes: spherical, cylindrical, and flat. This
> determines how the picture from the CRT gets distorted. The thing is, there's no
> guarantee that a CRT outputs a flat image. In fact most don't.

Right, at the moment the only basic shape missing in MAME, is the cylindrical shape.

> You might be familiar with controls such as 'trapezoid', 'rotation', and
> 'pincushion'. These, and other controls, can be used to distort the CRT image, with
> the goal to make the image look as flat as possible on the curved screen. You could
> even make it look close to what the screenshot you posted looks like if you wanted.

exactly. ridiculously enough, most people did not pay attention to this fact and started to post their "glorious" HLSL/GLSL settings with pictures of abnormal game-screen distortion and started to post threads about how bad/good are this shader system vs. that shader system etc., because it produced less moire/artefacts on the shadowmask or scanlines, not even knowing that even in RL the CRTs would have these kind of moire on the screens if they had a bad/defect chassis that controls the gun/beam. this was very annoying and i guess therefore Jezze created those parameters, so people can still have a strong curvature with perfect (or not so perfect) geometry, with the nice side-effect to reduce moire/artefacts to a minimum.

> As CRTs age, they start to distort more and more, in often unpredictable ways. What
> is common is for the screen to 'droop' or 'sag', so that the top corners of the
> screen start to sink downward. The corners and edges are prone to blowing inward or
> outward, making for some bizarre shapes (esp. combined with blooming). Basically, the
> weird geometry problems associated with CRTs has more to do with what the gun is
> doing rather than the screen curvature.

Yup... exactly.

> So really MAME should ideally have two parameters, one to set the screen curvature,
> and another that affects the CRT geometry. The CRT geometry would be a lot more
> complex. TVs have loads of geometry controls, like setting the pincushion of the
> top-left corner. (These would be in the service menu, a special menu for
> manufacturers and repairmen.) I guess to simplify things you could just have MAME do
> any arbitrary transformation on the screen, and then put it through the screen
> curvature.

Thats what we will have tommorow in the official release, at least a basic start for your good explanation here. it is maybe not perfect, but it is a very good start and i have hope, that we finally will see some "good" screenshots here, that doesnt show exaggerated pictures like Dullaron did here or the countless bulgy game screenshots before.