[Simh] Improved CRT simulation

[Lars Brinkhoff]

Paul Koning wrote:
>> I'm entertaining the idea of improving the CRT display simulation in
>> SIMH.  ...  Does the SIMH video framwork support using shaders
>> written in e.g. GLSL?
>
> I wrote a CDC DD60 simulation for use with DtCyber that attempts to
> model the CRT and spot behavior.  It does that by computing a 2-D
> Gaussian intensity distribution around the spot center, then sums that
> into the saved screen pixel value (with saturation).  And then that
> value is decayed exponentially.

Yes, I had something like this in mind.

> All this was done with wxWidgets and its direct bitmap access.  It may
> be that video shaders or GL machinery would be more efficient but I
> haven't studied how to do that.

I have played a bit with GLSL, so I think I could make it work.  In my
experience, it should be considerably more efficient.  But of course
it's futile if the right mechanisms in SIMH aren't in place.  I believe
SIMH relies on SDL2 which does offers access to shaders in some way.