jit.gl.cornerpin question

Feb 16, 2012 at 1:14am

jit.gl.cornerpin question

right away I wanna say: lovely object. Great stuff.

From what I can tell this is made specifically to transform jitter matrices for projection.

Is there a similar method with corner handles and such for a gl window? Or can this object be finagled into doing this?

I’m doing a big pure gl projection rather soon, so any pointers would be lovely. Cheers.

Feb 16, 2012 at 3:40am

hi wetterberg.

the cornerpin object handles gl textures exactly the same way as matrices.
simply send a texture to the object or set it’s @texture attribute to a named texture.

the object functions similarly to gl.videoplane.

Feb 16, 2012 at 7:32am

jit.gl.cornerpin is the cat’s pajamas (or it would be if cats had sharp corners)

I notice that it can be positioned, but not scaled or rotated – and changing jit.gl.render’s camera doesn’t affect it – so I guess it’s very much a 2D thing (unlike jit.gl.videoplane)

Feb 16, 2012 at 9:36am

well wasn’t i just in need of software keystone correction :)

Feb 16, 2012 at 12:47pm

yeah, I know it’s very similar to videoplane, what I am asking is:

Is there a way for me to transform my gl scene in this way without having to render the whole damned thing into a texture?

I am trying to project my gl objects – mainly meshes – for the same type of distortion – without having to capture teh whole thing to texture.

My hope was that since this was jit.GL I would be able to distort gl like this.
I dunno if I’m wording things right here, I’m sorry.

Feb 16, 2012 at 5:53pm

@pseudostereo – yes 2D only, so not entirely like gl.videoplane :)

@wetterberg – nope, you need to render your scene to a texture. fortunately, this process is greatly simplified with the gl.node object. simply drop a gl.node in your patch with it’s name attribute set to your current render context name, rename your render context to something new (only for your gl.render and your jit.window objects), set @capture 1 on your gl.node, and you’re done.

Feb 16, 2012 at 7:45pm

Hey guys,

Where can I find this [jit.gl.cornerpin] object?

Thank you!

Feb 16, 2012 at 9:06pm

Shame. I’ll see if I can come up with something by squeezing my matrix before it reaches the jit.gl.mesh and then leaving everything else as-is.

Either way I’ll try it out with jit.gl.node. The problem there is that jit.gl.cornerpin will always be used in live situations like this. But who knows, I may get lucky! :)

@ygreq: it’s a new object in 6.0.4

Feb 16, 2012 at 9:43pm

one thing i forgot to mention, in case it isn’t obvious, the gl.cornerpin should drawto the gl.render context, not the gl.node context.

Feb 16, 2012 at 10:07pm

“in case it isn’t obvious.”
you havin’ a laugh? Okay, I’m officially lost here.

I have *six* objects to deal with, and the naming isn’t at all obvious to me right now:


now (let me try to talk my way through this)

jit.gl.texture should share a context name with jit.gl.mesh.
jit.gl.mesh normally renders to jit.gl.render.
Now what we want to do is intercept this, run it through jit.gl.node, send it to jit.gl.cornerpin, which then sends it to jit.gl.render, forwarding it to jit.window.
yes? No? Am I close?

I’m sorry, but I hope you can see how the layperson is completely confused by this? :)

The naming there is totally beyond me; the jit.gl.cornerpin helpfile has no naming at all, and the jit.gl.node in its helpfile has one name and a different context…?

I just did the math though, and I can’t trial and error this, there’s way too many combinations, as far as I can tell.

Please help me out here. Cheers,

Feb 16, 2012 at 10:24pm

How about this?

– Pasted Max Patch, click to expand. –

DiGiTaLFX :)

Feb 16, 2012 at 10:54pm

beautiful – sums up all the different parts rather nicely! Thanks, I got it working thanks to you and Robert. This is ace – and oh my, I can feel it’s been some years since I’ve rendered to textures, this is blazingly fast!

Two questions:
1) If I were to do some shader work (attempt) to mess with this, it would be in-between jit.gl.node and jit.gl.cornerpin, correct?

2) More importantly, there seems to be something amiss here:
without me changing anything but the aforementioned parameters my navigation (space navigator, very close to examples done here, it’s done with jit.anim) is now *upside-down*, as if my image has been flipped somehow.

Does anyone know what could have caused this?

Feb 17, 2012 at 9:14am

Fab! Glad it makes sense now :)

1) Correct!

2) Ah yes! Seems that when sending a texture to the cornerpin it’s inverted. Easiest fix for now is to put the following slab between the Node and the Cornerpin to invert the image:

[jit.gl.slab output @rect 0. 1. 1. 0.]

I think this is something the Cycling folks need to fix?


Feb 17, 2012 at 9:37am

hey, I actually found a bug? That’s cool :)

cheers mate – any suggestions for slab effects?

Feb 17, 2012 at 10:13am

Try the following to add a bit of a glow to your scene:

– Pasted Max Patch, click to expand. –

And the sobel shader can be quite cool:

– Pasted Max Patch, click to expand. –
Feb 17, 2012 at 12:25pm

ah yeah, I remember now: v001.scanlines -> gauss == loveliness. And if you do individual control of the two width axes of gauss then you can do this rotating, swirly nonsense that looks really… what’s the word? J.J.Abrams’ey? :) Good stuff.

thanks for inspiring me!

Feb 17, 2012 at 6:40pm

hey guys, thanks for pointing out the bug and coming up with a temp workaround.
my apologies for letting this slip in there. we’ll get it fixed up for the next update.

Feb 18, 2012 at 10:59pm

When i use the mouse to set the corner pins: How would i save and restore the locations of the pins?

Feb 19, 2012 at 10:50pm

hi karl kliem. the mouse is simply setting the object’s corner attributes (upper_left, upper_right, etc), so you save and recall the same as you would any jitter attribute. freezing the attributes in the inspector is probably the easiest way to save a current state.

Feb 20, 2012 at 9:48am

hi robert,

thanks for the suggestion. however, i need to provide an easy user interface for a non-technician to set up the projection mapping of several canvases right before the concerts. it would be great if jit.gl.cornerpin could output the cornerpin locations out of the dump outlet, so i could automate saving the values.

Feb 20, 2012 at 3:57pm

+1 for dump output (or attrui saving which would do the trick as well)

Feb 20, 2012 at 5:39pm

Hi Karl

How about this?

– Pasted Max Patch, click to expand. –


Feb 20, 2012 at 5:52pm

thanks! i checked the reference and the wheel menu, but these messages are not mentioned. how did you find out?

Feb 20, 2012 at 6:01pm

@digitalfx: cheers man!

does this get* business apply to all jit parameters/objects?

Feb 20, 2012 at 6:57pm

here’s a way of storing and recalling with pattrstorage and preset

– Pasted Max Patch, click to expand. –
Feb 20, 2012 at 7:39pm

yes, all jitter attributes can be recalled this way.
take a look at the documentation on attributes if you need more info:


Mar 4, 2012 at 6:03am

Thanks for this object! I’ve been wanting something just like this for years. Could be accomplished before but so much easier now. And .gl!!!!

Mar 5, 2012 at 6:44pm

You can attach a pattr object to any Jitter attribute as well, as long as the object has a scripting name. See the attached. This allows you to easily set up a pattrstorage object to save state.

– Pasted Max Patch, click to expand. –
Mar 5, 2012 at 9:05pm

i see, nice!

just starting to learn the pattr family here. about time after all those years…

Mar 5, 2012 at 9:24pm

Ha! I would have loved to have been able to work this on friday – When you start getting into animating with jit.anim.drive and moving objects, sometimes “moveto” gets a bit hairy, since you don’t really know the absolute position – I do now, I guess :)

Mar 9, 2012 at 10:41pm

Ah, I never knew that! How come the following doesn’t work then?

– Pasted Max Patch, click to expand. –
Sep 4, 2012 at 11:29am

Is there any way of setting the uvs for the plane?

Nov 5, 2013 at 4:09pm

one year later…
with the camera


– Pasted Max Patch, click to expand. –


Jan 30, 2014 at 4:16am


How can I have a black background with jit.gl.cornerpin? Mine is grey, not very useful for mapping!

Thank you in advance,

Jacques Hoepffner

Jan 30, 2014 at 5:40am

Hello Hoepffner,
you can use the @erase_color attribute in the main [jit.gl.render] to set the window background color, and use the same attribute in a [jit.gl.camera] object to assign the cornerpin’s background a different color.


– Pasted Max Patch, click to expand. –


Feb 26, 2014 at 10:41am

I wish jit.gl.cornerpin could output to other destinations than jit.gl.render. I have this multidisplay rendering setup where 1 output window spans all 4 displays. I can use cornerpin as long as my corners stay inside their respective display portion (ie. scaling down the texture). But if I scale up instead of down textures start overlapping with the adjacent display’s portion.

I’d like to use something cornerpin-like to compensate for projector tilt without using the projectors keystone correction. I tilt heavily and keystone then shrinks the image a lot, making inefficient use of the available pixels and light output.

Below ‘s my rendering setup. The node contains the geometry to be rendered. 4 camera’s render views from 4 positions. Texture goes through a couple of slabs, into 4 videoplanes positioned to match the 4 display outputs.

Any ideas on how I could implement cornerpin-like adjustments that allow me to stretch the textures outside their display portion?


– Pasted Max Patch, click to expand. –


Feb 26, 2014 at 4:16pm

you could always capture cornerpin to a texture with gl.node, and then send to another cornerpin. or am i missing something?


– Pasted Max Patch, click to expand. –


Feb 27, 2014 at 12:36am

Ah that’s fantastic! I miss-interpreted your phrase above: “the gl.cornerpin should drawto the gl.render context, not the gl.node context”. Tanx.

Feb 27, 2014 at 12:39pm

I had trouble getting the mapping I need because cornerpin distorts the texture in ways that don’t work in my situation. I need to move the corners only horizontally, which also introduces a vertical distortion in the texture. That messes up things for me.

I managed to get the correction I need by setting frustum on the camera and sending the texture into a jit.gl.nurbs plane that I deform. Here the texture only morphs horizontally when the corners move horizontally. Great.

Now the issue is again that the nurbs corners extend out of their display area. Any tips as how to I could clip the nurbs planes to a ceratin portion of my output window?

Feb 28, 2014 at 9:48am

again, i would say capture the nurbs to a gl.node texture (make sure you set the gl.node @adapt 0 and dims to the individual display dims). this should handle clipping of geometry extending beyond the display area.

Mar 1, 2014 at 2:50am

Great, that works. Tanx!

In case anyone needs something like that, here’s a patch:


– Pasted Max Patch, click to expand. –


This clips the rendering to the left half of a 640×240 window. Substitute the cornerpin for your geometry.

Mar 20, 2014 at 3:26pm

just had a little play with corner pin and my projector. I am guessing from looking around the object that it wont do more than 4 pins?


Mar 21, 2014 at 12:17pm

no, just the 4 corners.
however you can do something like perform your major warping with the cornerpin, capture that to a texture, and then perform fine-tune warping using gl.mesh or gl.nurbs.

this patch uses an awesome nurbs-phys.multiple patch posted by user matmat to do warping.

note that capturing a cornerpin to a gl.node context disables the mouse interaction. this should be fixed in a future update.


– Pasted Max Patch, click to expand. –



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