In Gem, does anyone know how pix_levels works. I just want to kill all the reds or greens in a video. I don't understand the floor/ceiling stuff.
Also does anyone know how to do the screen effect, similar to add....? Thanks
Peter Forde wrote:
In Gem, does anyone know how pix_levels works. I just want to kill all the reds or greens in a video. I don't understand the floor/ceiling stuff.
if you want to just remove all the greens and reds in the video, why not texture it on something that has no red/green components (like a [square] with [color 0 0 1]) - default texturing does a per-channel multiplication with the underlying color (so if the the channel "red" is zero for the geo, than the you won't have any red-component in the displayed image either) if you want to burn CPU-cycles, you could also use [pix_gain] and set the gains to "0 0 1"
Also does anyone know how to do the screen effect, similar to add....?
i don't know what the "screen effect" is.
mfg.asdr. IOhannes
On 4/5/06, IOhannes m zmoelnig zmoelnig@iem.at wrote:
if you want to just remove all the greens and reds in the video, why not texture it on something that has no red/green components (like a [square] with [color 0 0 1]) - default texturing does a per-channel multiplication with the underlying color (so if the the channel "red" is zero for the geo, than the you won't have any red-component in the displayed image either) if you want to burn CPU-cycles, you could also use [pix_gain] and set the gains to "0 0 1"
This is very efficient on CPU. But, if one needs to add saturation or contrast in Gem, he needs to use [pix_levels] or [pix_gain] for saturation and [pix_curve] for contrast, right ?
aalex
Alexandre Quessy wrote:
On 4/5/06, IOhannes m zmoelnig zmoelnig@iem.at wrote:
This is very efficient on CPU. But, if one needs to add saturation or contrast in Gem, he needs to use [pix_levels] or [pix_gain] for saturation and [pix_curve] for contrast, right ?
they need to use [pix_saturate] (and once gem-0.91 is out (hopefully soon!!) you don't even need to know how to compile Gem in order to use it ;-))
mfgasdr. IOhannes
On Wed, 5 Apr 2006, Peter Forde wrote:
Also does anyone know how to do the screen effect, similar to add....?
It's a multiply in the complement colorspace.
You can see it as an example presented in the GridFlow paper presented at PdConvention04 and Piksel05:
http://artengine.ca/matju/graz/GridFlow_PdConvention04.pdf
It's on page 6.
_ _ __ ___ _____ ________ _____________ _____________________ ... | Mathieu Bouchard - tél:+1.514.383.3801 - http://artengine.ca/matju | Freelance Digital Arts Engineer, Montréal QC Canada
On Apr 5, 2006, at 5:55 AM, Peter Forde wrote:
In Gem, does anyone know how pix_levels works. I just want to kill
all the reds or greens in a video. I don't understand the floor/ ceiling stuff.
...ok, no one answered how pix_levels works, so I'll try...it's alot
like the "levels" option in Gimp or photo$hop: they all allow you to
control the levels of color channels, either individually or together...
...[pix_levels] has a few different modes: auto, auto+uniform,
uniform, and "other"...when "auto" is on, the object automagically
assumes it knows most of the bandwidth you'd like to deal with, and
so you really just need to tell it what to do with individual
channels...for example, if you just want to remove the red channel,
set auto on, then send [0 1 0 0< to the third inlet...(this reminds
me that it might be better to have a named message here, so maybe in
the future we can have a [red 0 1 0 0< to do the same thing)
...the uniform mode takes one message for the RGB channels together,
and this goes to the 2nd inlet of [pix_levels]...this works more as
an overall lightness/darkness control for the image...
...the floor/ceiling stuff has to do with how much bandwidth of the
color(s) you're dealing with, and you usually have seperate in/out
floor/ceilings...so, if you have [0 1 0 1<, you have the full
spectrum of the channel output...
hth,
james
-
Alexandre Quessy -
IOhannes m zmoelnig -
james tittle -
Mathieu Bouchard -
Peter Forde