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looking for a software-scope

Jim the Oldbie

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#21
What the hell, here's a screen shot of the Abox setup:

Abox Quad Vector Scope.gif

...And here's a little ani-GIF of the scope in action, playing this part of BS&T's "God Bless The Child" in a short loop:

QuadScope.gif

(It's a little choppy, because I reduced the frame rate to 15 fps to keep the file size down.)

You can see David's solo vocal front & center, then the piano on the right, between front & rear. When the band comes in, the channel vectors are just visible as a large 'X' across the screen. But they're not as well defined as they are on an old-school scope, because there's an important feature of the analog CRT that's missing from this emulation. Can anyone guess what it is? :)
 
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Jim the Oldbie

400 Club - QQ All Star
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#27
You got it Duncan!

On a CRT screen, because of the way the phosphor brightness decays over time (like a comet's tail), it appears brighter in the areas of the screen where the beam visits more often, to keep it lit up. This provides a useful contrast, and more visual information. In my little computer scope, when the lines are drawn, they stay drawn at full brightness until they are replaced when the next video frame comes along, so there's no contrast anywhere.

With that said, I'm sure that an emulation of phosphor persistence is probably not much of a challenge to a graphics programmer, but I'm afraid that's beyond what I know anything about. I think I've got the correct "beam-steering" model up there; hopefully someone can pick up the torch and make it look better.
 
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DuncanS

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#29
You got it Duncan!

On a CRT screen, because of the way the phosphor brightness decays over time (like a comet's tail), it appears brighter in the areas of the screen where the beam visits more often, to keep it lit up. This provides a useful contrast, and more visual information. In my little computer scope, when the lines are drawn, they stay drawn at full brightness until they are replaced when the next video frame comes along, so there's no contrast anywhere.

With that said, I'm sure that an emulation of phosphor persistence is probably not much of a challenge to a graphics programmer, but I'm afraid that's beyond what I know anything about. I think I've got the correct "beam-steering" model up there; hopefully someone can pick up the torch and make it look better.
I'm an Electronic Design Engineer so have an unfair advantage :geek:
 
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