bryanteoh

I'm making a grand effort to transition into doing more stuff in the gl domain. This is a two part question.

1)I have a series of moving gridshapes which I've captured to a texture and processed with a slab. Is there a way I can now set this scene as the alphachannel for another slab, or is this something that would be better done in a matrix?

2)I'm trying to learn more about shaders and figure out how some of the ones that come with jitter work. Doing this often involves creating a patch just to figure out what parameters the shader will accept, then opening the shader in a text editor and trying to figure out what those parameters do and how they work. Am I missing out on some sort of shader help files or list?

I'm making a grand effort to transition into doing more stuff in the gl domain.  This is a two part question.

1)I have a series of moving gridshapes which I've captured to a texture and processed with a slab.  Is there a way I can now set this scene as the alphachannel for another slab, or is this something that would be better done in a matrix?  

2)I'm trying to learn more about shaders and figure out how some of the ones that come with jitter work.  Doing this often involves creating a patch just to figure out what parameters the shader will accept, then opening the shader in a text editor and trying to figure out what those parameters do and how they work.  Am I missing out on some sort of shader help files or list?  

set-alpha-channel-on-the-gpu

ok, I've found a sort of workaround I think. I'm taking the slab with the shapes in it (all of which are white) and am using op.mult.jsx to multiply that by the source video I wanted to create the alphachannel for. Now I have a black background with a bunch of video shapes. I'll probably use andrew bensons lumagate trick to key out the black background and composite the whole thing over the video I would have alphablended with the video fragments.

I feel like there is a more direct way to do this, but for now it will have to work. I'll post an example once I get it working. Hopefully someone will have a better idea?

ok, I've found a sort of workaround I think.  I'm taking the slab with the shapes in it (all of which are white) and am using op.mult.jsx to multiply that by the source video I wanted to create the alphachannel for.  Now I have a black background with a bunch of video shapes.  I'll probably use andrew bensons lumagate trick to key out the black background and composite the whole thing over the video I would have alphablended with the video fragments.

I feel like there is a more direct way to do this, but for now it will have to work.  I'll post an example once I get it working.  Hopefully someone will have a better idea?


On Tue, May 6, 2008 at 5:30 AM, bryanteoh wrote:

> ok, I've found a sort of workaround I think. I'm taking the slab with the

> shapes in it (all of which are white) and am using op.mult.jsx to multiply

> that by the source video I wanted to create the alphachannel for. Now I

> have a black background with a bunch of video shapes. I'll probably use

> andrew bensons lumagate trick to key out the black background and composite

> the whole thing over the video I would have alphablended with the video

> I feel like there is a more direct way to do this, but for now it will

> have to work. I'll post an example once I get it working. Hopefully

On Tue, May 6, 2008 at 5:30 AM, bryanteoh  wrote:

>
> ok, I've found a sort of workaround I think.  I'm taking the slab with the
> shapes in it (all of which are white) and am using op.mult.jsx to multiply
> that by the source video I wanted to create the alphachannel for.  Now I
> have a black background with a bunch of video shapes.  I'll probably use
> andrew bensons lumagate trick to key out the black background and composite
> the whole thing over the video I would have alphablended with the video
> fragments.
>
> I feel like there is a more direct way to do this, but for now it will
> have to work.  I'll post an example once I get it working.  Hopefully
> someone will have a better idea?
>

Ok, here's a patch. Don't worry about the crap in the subpatcher. I basically need to figure out how to key the slab on to another slab, but am having difficulty figuring out how to do it in shader land. Also, if anyone has any pointers on how to reduce the jaggies on the shapes, I would appreciate it.

I apologize in advance because I'm sure these questions have been asked before, but I've been unable to find them in the archives.

Ok, here's a patch.  Don't worry about the crap in the subpatcher.  I basically need to figure out how to key the slab on to another slab, but am having difficulty figuring out how to do it in shader land.  Also, if anyone has any pointers on how to reduce the jaggies on the shapes, I would appreciate it.  

I apologize in advance because I'm sure these questions have been asked before, but I've been unable to find them in the archives.


you seem to have a good grasp of matrix side of things and thats good,

0. you're jit.gl.render gets a bang,erase but the order is wrong. everything

you do in your drawing seqance should happen *between* the bang and erase to

the render. also research the use of automatic or layer attribute to jit gl

1. you dont need a texture before the slab, a slab is a kind of abstraction

of texture>geometry>texture. just pass the name of the texture straight into

jit.gl.texture/slab>jit.matrix>jit.unpack>jit.pwindow*4+jit.fpsgui

make sure to gate or erase it after usage, readback from opengl to matrix is

3. for debuging and undertsanding the number one rule is to throw out

everything thats not relevente to the problem. your subpatch is distracting

i uderstand i didnt give you a stright answer to your problem, your very

On Wed, May 7, 2008 at 10:34 AM, bryanteoh wrote:

> Ok, here's a patch. Don't worry about the crap in the subpatcher. I

> basically need to figure out how to key the slab on to another slab, but am

> having difficulty figuring out how to do it in shader land. Also, if anyone

> has any pointers on how to reduce the jaggies on the shapes, I would

> I apologize in advance because I'm sure these questions have been asked

> before, but I've been unable to find them in the archives.

you seem to have a good grasp of matrix side of things and thats good,
couple of things

0. you're jit.gl.render gets a bang,erase but the order is wrong. everything
you do in your drawing seqance should happen *between* the bang and erase to
the render. also research the use of automatic or layer attribute to jit gl
objects.

1. you dont need a texture before the slab, a slab is a kind of abstraction
of texture>geometry>texture. just pass the name of the texture straight into
it. like @texture keytext

2.to debug opengl matrices i often use
jit.gl.texture/slab>jit.matrix>jit.unpack>jit.pwindow*4+jit.fpsgui

make sure to gate or erase it after usage, readback from opengl to matrix is
expensive.

3. for debuging and undertsanding the number one rule is to throw out
everything thats not relevente to the problem. your subpatch is distracting
to the problem.

i uderstand i didnt give you a stright answer to your problem, your very
close

On Wed, May 7, 2008 at 10:34 AM, bryanteoh  wrote:

> Ok, here's a patch.  Don't worry about the crap in the subpatcher.  I
> basically need to figure out how to key the slab on to another slab, but am
> having difficulty figuring out how to do it in shader land.  Also, if anyone
> has any pointers on how to reduce the jaggies on the shapes, I would
> appreciate it.
>
> I apologize in advance because I'm sure these questions have been asked
> before, but I've been unable to find them in the archives.
>
>
>

THANK YOU THANK YOU THANK YOU!!!! The layer attribute was exactly what I needed. I was also able to resolve my issue with the jaggies...it wasn't an issue with antialiasing...just needed to increase my texture dimensions.

thanks for all the other suggestions as well. They're useful patching 'isms'. 

THANK YOU THANK YOU THANK YOU!!!!  The layer attribute was exactly what I needed.  I was also able to resolve my issue with the jaggies...it wasn't an issue with antialiasing...just needed to increase my texture dimensions.  

thanks for all the other suggestions as well.  They're useful patching 'isms'.  


set alpha channel on the gpu