Andrew Benson

Here's a simple demo patch that shows how to set up the to_texture 

message to perform feedback processing with a gl context. I've included 

2 textures, one for using fullscreen mode, and then the other for using 

the 640 480 window. This technique of switching textures allows for 

resizing the jit.window without getting those error messages. With a 

little ingenuity, you can be kicking out some swirly 3-D psychedelic 

Hi Jitter-fans,
Here's a simple demo patch that shows how to set up the to_texture 
message to perform feedback processing with a gl context.  I've included 
2 textures, one for using fullscreen mode, and then the other for using 
the 640 480 window. This technique of switching textures allows for 
resizing the jit.window without getting those error messages.  With a 
little ingenuity, you can be kicking out some swirly 3-D psychedelic 
visuals in no time.

Have fun, and Happy Patching!
Cheers,
Andrew B.


gl-feedback

thanks for the clear gl_feedback_example!

the texture switching method is exactly what i needed.

thanks for the clear gl_feedback_example!
the texture switching method is exactly what i needed.

So much food for thought. I will come back with more questions later 

So much food for thought.  I will come back with more questions later  
today ;-)

Hi Andrew, I'm only getting these errors:

jit.gl.render: building GL on window "foo"...

warning: method screen_grab called on invalid object

jit.gl.render: building GL on window "foo"...
warning: method screen_grab called on invalid object
warning: method screen_grab called on invalid object
warning: method screen_grab called on invalid object
...
...
etc.

the 'usetexture dst' message box needs to be sent to the render befor 

best achieved by putting a 'loadbang 0' to the fullscreen togglebox..

the 'usetexture dst' message box needs to be sent to the render befor  
you start the feedback.
best achieved by putting a 'loadbang 0' to the fullscreen togglebox..

> best achieved by putting a 'loadbang 0' to the fullscreen togglebox..

i should really stop typing emails with my nose;.)

i meant 'loadmess 0' of course.
i should really stop typing emails with my nose;.)

If I understand well, to_texture can only be used to do whole scene 

feedback. The capture to texture is working fine so far. I have one 

> Personally, I like to render to a pbuffer.

I have looked on the web for pbuffer and can't figure out what you 

nb It seems that the getparamlist message to jit.gl.slab does not 

If I understand well, to_texture can only be used to do whole scene  
feedback.  The capture to texture is working fine so far.  I have one  
more question:

I have looked on the web for pbuffer and can't figure out what you  
are talking about.

nb It seems that the getparamlist message to jit.gl.slab does not  
output anything...


Here's a glossary of graphics card terms:

http://www.gpgpu.org/w/index.php/Glossary#FBO

page, I learned a new one: FBO . Seems to be the best place to get a

> nb It seems that the getparamlist message to jit.gl.slab does not

The best way to figure out what params a shader has is to open the

file in a text editor (I prefer Text Wrangler on OSX). It's easier to

see there than as a list in the maxwindow.

Here's a glossary of graphics card terms:
http://www.gpgpu.org/w/index.php/Glossary#FBO .  After looking at this
page, I learned a new one: FBO .  Seems to be the best place to get a
render to texture now-a-days.

> nb It seems that the getparamlist message to jit.gl.slab does not
> output anything...

The best way  to figure out what params a shader has is to open the
file in a text editor (I prefer Text Wrangler on OSX).  It's easier to
see there than as a list in the maxwindow.

Can I shamefully ask for a small sample code of pbuffering? It all 

sounds great, I understand the concept, but to see a real example 

will help me to deduce more usage of the openGL book started today 

Can I shamefully ask for a small sample code of pbuffering?  It all  
sounds great, I understand the concept, but to see a real example  
will help me to deduce more usage of the openGL book started today  
and ways to apply that in jitter.

As I'm sure you've discovered, it's used alot in the computer gaphics

literature for multipass rendering. If you can get your hands on GPU

Gems 2 from your local library I think you'll find the pages 541-543

decently descriptive as it also has code sinppets. (I'm not sure, but

NeHe might have something about this as well...in any case it's a

As I'm sure you've discovered, it's used alot in the computer gaphics
literature for multipass rendering.  If you can get your hands on GPU
Gems 2 from your local library I think you'll find the pages 541-543
decently descriptive as it also has code sinppets.  (I'm not sure, but
NeHe might have something about this as well...in any case it's a
great resource for opengl manips).

I have read the book chapter but I still find no connection on using pbuffer

Wesley, could you help to give a bit more hint on utilizing pbuffer ? Should

we use jit.gl.sketch or we have to write our own (or find) an external to

by the way, in my days of experiementing with rendering to texture, I have

encountered an error message saids "jit.gl.pbuffer: error updating bound

texture: GL Error: Stack overflow". I wonder if there is an implicit object

named jit.gl.pbuffer but I have found no entry of documentation about it...

ps: Thanks to Andrew for your patch. I have made the "to_texture" working

now, but seems it only work on the display buffer while my application need

to a capture from an offscreen buffer (e.g. render to texture from camera A

and render scene in camera B with the captured texture)

I have read the book chapter but I still find no connection on using pbuffer
in Max/Jitter environment....

Wesley, could you help to give a bit more hint on utilizing pbuffer ? Should
we use jit.gl.sketch or we have to write our own (or find) an external to
work on it ?

by the way, in my days of experiementing with rendering to texture, I have
encountered an error message saids "jit.gl.pbuffer: error updating bound
texture: GL Error: Stack overflow". I wonder if there is an implicit object
named jit.gl.pbuffer but I have found no entry of documentation about it...

ps: Thanks to Andrew for your patch. I have made the "to_texture" working
now, but seems it only work on the display buffer while my application need
to a capture from an offscreen buffer (e.g. render to texture from camera A
and render scene in camera B with the captured texture)

I don;t have the book in front of me right now, but let me see if I

can remember. It went a little something like this:

Rendering to a pbuffer in the traditional fashion requires a new

opengl context to be set up. This causes massive overhead a slow

applications. Using the opengl aux buffers liek AUX0 etc gets you the

same effect but without the context switches. On the aforementioned

pages, there was code as to how to set this up. Unfortunately, to do

this in jitter right now, you're gogin to have to write your own

I don;t have the book in front of me right now, but let me see if I
can remember.  It went a little something like this:

Rendering to a pbuffer in the traditional fashion requires a new
opengl context to be set up.  This causes massive overhead a slow
applications.  Using the opengl aux buffers liek AUX0 etc gets you the
same effect but without the context switches.  On the aforementioned
pages, there was code as to how to set this up.  Unfortunately, to do
this in jitter right now, you're gogin to have to write your own
external as far as I know.

this isn't working for me at all. when i switch to fullscreen, i get the grid texture on the vidplane and the max window fills with

jit.gl.texture: error entering unbind: GL Error: Invalid value

os x 10.4.4, albook 1.67 feb 05, newest m/m/j.

this isn't working for me at all.  when i switch to fullscreen, i get the grid texture on the vidplane and the max window fills with

jit.gl.texture: error entering unbind: GL Error: Invalid value
jit.gl.texture: error entering unbind: GL Error: Invalid value
jit.gl.texture: error entering unbind: GL Error: Invalid value
jit.gl.texture: error entering unbind: GL Error: Invalid value
jit.gl.texture: error entering unbind: GL Error: Invalid value
jit.gl.texture: error entering unbind: GL Error: Invalid value
jit.gl.texture: error entering unbind: GL Error: Invalid value

os x 10.4.4, albook 1.67 feb 05, newest m/m/j.


You have to muck with the textures a bit to get it to work. I too had

the same errors but was eventually able to get it to work.

You have to muck with the textures a bit to get it to work.  I too had
the same errors but was eventually able to get it to work.

I believe I never used the fst texture, just the dst texture. I also

messed with the texture dims. I don't remember the specific settings,

but that's what I messed with. Also, when you go fullscreen, the

context is rebuilt, so you may have to reregister the texture names by

I believe I never used the fst texture, just the dst texture.  I also
messed with the texture dims.  I don't remember the specific settings,
but that's what I messed with.  Also, when you go fullscreen, the
context is rebuilt, so you may have to reregister the texture names by
clicking on the appropriate messages.

this is the sort of thing that just makes me feel like an idiot w/r/t the gl stuff. i get weird errors and random crashes, and when i report them i get the digital equivalent of blank stares.

wes, can you post a version of this that actually does work? TIA.

this is the sort of thing that just makes me feel like an idiot w/r/t the gl stuff.  i get weird errors and random crashes, and when i report them i get the digital equivalent of blank stares.

wes, can you post a version of this that actually does work?  TIA.


thanks andrew. the dual texture concept saved the day for a readback thing I needed. my head was getting sore bc. i was trying to change dims on the texture, which, for whatever reason, it did NOT like.

thanks andrew.  the dual texture concept saved the day for a readback thing I needed.  my head was getting sore bc. i was trying to change dims on the texture, which, for whatever reason, it did NOT like.

GL Feedback