Split properly an image with Matrox DH2Go / TH2Go

  • Tech Staff

    Hello maiami

    I can publish the inputs in Quartz Composer but that wouldn't work in Isadora out of the box, I tried it. You have to change the QC patch first, and at the moment I don't have time to sit down and look at it.


  • Hi Michel,
    thank you for answering
    the thing is that QComp is a mystery for me...
    To precise : i do have the Core Video upgrade.

    best - maia

  • Beta Tester

    Hi Maia,

    This should do it:

  • Hi Matthew,
    thanx a lot
    it's getting better, but i still do have a thin line (black or bright, depending on ajustments), that i can't make softer....
    As i'm searching step by step, maybe i missed something?
    Also if i remove the pixel chopper, i have full size image on each projector (so twice), even if in stage pref. i did split left half / right half....
    In attached files, a picture of the projection + my patch (is it absurd?)

    f9de47-img_5718.jpg 6007c7-izz2projpatch120113.tiff

  • hi
    i did find seb actor with input in skulpture post on this discussion :

    in case of...

  • Tech Staff

    I had a go at editing the patch @michel but it was taking a long time and a lot of number crunching. (it's always strange for me working on someone else quartz patch)

    I have sent @maiami as simple but effect patch that uses a picture (.gif) file with a black and white ramp; which can be zoomed and panned for each stage (projectors 1 and 2).
    For those who want to try it; here it is....

  • Beta Tester

    Hi Maia,

    Unfortunately, I'm not sure why that line is appearing. I have used that Quartz comp many times without that issue and I don't have time right now to try and troubleshoot what is going on but perhaps someone else can weigh in.

  • @maiami

    What kind of projectors are you using ? LCD or DLP ?
    I had the same problems when using LCD projectors with softedge systems developped with DLPs
    @MatthewH : Are you maybe always using DLPs for softedge ?

  • Tech Staff

    @MatthewH I am getting the line to. Strange. I can see how the Quartz actor is supposed to work but it just inst behaving quite right.

  • Hi
    @ Medhi : yes i'm using LCD projectors...
    i had a new surprise about that : in french i'd say "irisation", meaning that depending on where you are in the room the color (the color temperature you see) of the projector changes, which is, of course, really wired with 2 proj splitting one image on its middle... (would be maybe less with DLP, what do you think?)

    For the soft edge, I'm at this point using a mix between different parts of your solutions guys ;-) : Chop Pixels + alpha mask with a gradient (@Skulpture, no zoonmer) + 3D quad distort. It's not so bad, but not perfect yet, i still have a more shiny, or dark (depending on ajustments) stripe at the overlapping point...

    @ Skupture : i did make some new ramp, more thin (cause my overlappping area is not so large), but i'm not sure of the better way to do it : i did, in Photoshop, a common gradient, saved in Gif with "Black&White"+transparency settings (see in attached file) : any mistake, or reason to have a shiny line when overlapping?
    cf747b-psgifsettings.tiff 9a355b-ramp6.gif

  • Tech Staff

    It's good that you are getting closer to your solution. I am sure you will sort it out soon.

    Those gif settings look right to me. As for the shiny line.... hard to say really without seeing it in real life and standing looking at your isadora patch.

  • Instead of real life, some pictures... ;)
    It's less shiny then it was with Matthew solution, or without any alpha mask, but still there.
    The 1st one is with the gradient example I sent last post, the 2nd is with an even thiner one.

    And the patch is attached also....

    Thank you (all of you) for searching and support!

    a38ce2-img_5719.jpg 3cc726-img_5720.jpg 55c735-izzpatch160113.tiff

  • Tech Staff

    I would try putting a contrast adjust after the mask picture player (the black and white fade gif file)

    You can control the brightness of the mask then.

  • I tried... not so good. it changes but in any ways i still have a line.
    the only efficient setting is the output max... affecting the complete picture, even putting it just after the ramp.
    I'll maybe try to have a mask with a lowest opacity directly in Photoshop, what do you think?
    I try and tell you.

    Is the patch correct?

  • Also, does Isadora support png?
    I did try, unsuccesfully...

  • Hi, for the "irisation",

    I think it's because that the surface you project on is "reflecting" the video in a different way depending on the angle between the source and your point of view...
    I did a little schema, I don't know how to say this !
    I have no solution to this... ( put your beamers super far... )


  • yes, you're right, i did get that ; i'm on a cyclorama... and not in back (retroprojection) but in front so it's not the better way...
    But thanx for the shema, i'll use it to explain that to my director!!

    and if i use this f***ing matrox + 2 beamers system is because i can't be far, for a wide screen format...

    but i'm not searching any solution for that (the only i can imagine right now would to put all the audience on a same line ;-), we'll put a bit of light upon the video which does not need complete darkness...

    no, my real problem is still this overlapping line...

  • Hi, back after a while, i did post on another discussion the method i finally used, thanks to Skulpture tips

    i'll post pictures asap (i'm rebuilding it in a new venue)

    Hope it will help further... and thanks a lot for helping.


  • One thing this reminds me of is a color space your using for your images. Is it linear colorspace? If it is not, you may not get what you expect in the overlap. I'd say to solve this one should have a ramp mask fine-tuned to your images and screens.


  • to be sincere i didn't even think about it, but it's solved anyway! ;)