As always, constructive criticism is appreciated

> Date: Sat, 23 Jan 2010 01:15:09 +0000
> From: claudiusmaximus@goto10.org
> To: james@4thharmonic.com
> CC: pd-list@iem.at
> Subject: Re: [PD] Drawing lines in gem with alpha fade
>
> James Dunn wrote:
> > Thanks - it's interesting but doesn't seem to do quite what I need. Even
> > with a maximum alpha value, I still want the lines to stay on full
> > brightness for longer. Also, I'm drawing some fine lines and there are
> > some weird artefacts like blocks appearing in the trail. Is there
> > something else I could try?
>
> This is probably caused by the texture being 8-bit per channel, so decay
> coefficients are quantized in 1/256 increments, which makes long decay
> times hard to achieve (the slowest decay's coefficient is 255/256, which
> isn't as close to 1.0 as you want, I guess).
>
> You could keep some data about the history of each line segment
> (position, time created, colour, etc), and draw them all fresh each
> frame - this will be much less efficient than texture feedback but you
> would have more control over the fade, with the possibility to do
> things like change colour (not just alpha) over time with
> other-than-exponential decay curves, etc.
>
> Probably pd/doc/Gem/02.advanced/20.double-gemhead_vs_repeat.pd helps.
>
> If that gets too slow you could combine the drawing of the line segments
> into one glBegin/End block at the price of some flexibility. And if
> that gets too slow, there's probably something that can be done with
> vertex arrays/buffers or whatever they're called (if it's even possible
> in Gem - I'm not sure, but I'd like to find out!).
>
>
> Claude
>
> >
> > Quoth cyrille henry, on 22/01/10 21:45:
> >> have a look at example 07.texture/08.MotionBlur.pd
> >> all you have to do is remplace the teapot with a line that you can
> >> draw or not (to make it fade out)
> >>
> >> Cyrille
> >>
> >>
> >> James Dunn a écrit :
> >>> I've been sending x/y values to [curve] to draw some lines in gem and
> >>> the only way I've been able to get them to stay rendered is to use
> >>> single buffer mode using [buffer 1( messaged to [gemwin].
> >>>
> >>> Can someone suggest a better method using double buffer perhaps? I
> >>> would like the lines to fade out after some seconds. I looked at
> >>> pix_snap2tex and gemframebuffer but could only get one line rendered.
> >>> Is this possible with the particle objects?
> >>>
> >>> thanks
> >>>
> >>> James
>
> --
> http://claudiusmaximus.goto10.org
>
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