Slab Help!!!

    Pierre Alexandre Tremblay
    Jan 23 2006 | 10:24 am
    Dear Jitterers
    I am really seduced by the GPU processing, especially right now because I work on multimedia installations and want to free as much CPU for the audio part. It seems full of potential, but I find the learning curve quite steep. For example, the amazing examples by Andrew are so elegant, but there is lots of features in it I can't find in the documentation, for instance, the @capture that can save my day.
    This is not a complain, but just a stucked poor coder who needs help to go further... What I do right now is designing the patch in Jitter matrix, then port is to slab. I know I will probably drop this approach quite soon, but my openGL licks are not near as my matrix knowledge.
    I don't want to be given the patch, but I want to know where to find a good tutorial/reference for that whole world of openGl objects. Is there something I should read after the documentation to help me design my really simple patches.
    Any pointer is welcome.
    pa
    ps For example, I want to move around a jpeg right now, to use it as a mask on an incoming film. I manage to put my jpeg as a texture on a jot.gl.gridshape plane object, then position and resize my plane. But I have erasing problems, when the new size is smaller than the previous... we can see leftovers of the previous frame...
    • Andrew Benson
      Jan 23 2006 | 11:10 pm
      Hi Pierre, It's good to hear that you are interested in this. I strongly recommend grabbing a copy of the orange book, OpenGL Shading Language, by Randi J. Rost. You will want to pay special attention to the chapters 3,5, and 16. I tend to keep this near my desk, and refer to it often.
      The same could be said for the red book as well. This book goes a great distance in demystifying the OpenGL pipeline, and explains the more low-level jit.gl.sketch commands.
      The important thing to remember with GLSL is that you are dealing with each pixel individually. A shader program doesn't have memory of its own. This can make them alternately very straightforward or very troublesome to implement. If you are having trouble implementing something specific, I encourage you to post to the list.
      If there is any specific aspect of jitter and OpenGL that you feel could be explained in more detail, please let us know. I can always add it to my agenda for weekly examples.
      Cheers, Andrew B.
    • williamshome
      Jan 24 2006 | 5:42 am
      Hi Andrew,
      I have checked out your example too. It is a very nice patch on making use of @capture and slab to generate effect out of a 3d geometry.
      However, I am working on something I want to render a scene into texture and use it in later rendering. I have been told of the "to_texture" message of jit.render and have checked out the example in jitter tutorial. But I still could not figure it all out and always produce error message, "warning: method screen_grab called on invalid object".
      Is it possible to have a more detailed example use of the message ?
      (^_^) William
    • vade
      Jan 24 2006 | 5:46 am
      Hi.
      to_texture is currently broken, to everyones dismay. We all patiently await c74s fix. currently there is no way to render a whole scene to a texture on the GPU.
      yes.
      this makes baby jesus cry.
      tsk tsk.
      v a d e //
      www.vade.info abstrakt.vade.info
    • williamshome
      Jan 24 2006 | 5:52 am
      I see. But why would the example "jit.gl.render.radialblur" still manage to use it ?
      (^_^) William
    • randall jones
      Jan 24 2006 | 6:15 am
      I am using to_texture regularly. The destination context size must match the texture size exactly.
      -Randy
    • vade
      Jan 24 2006 | 6:32 am
      can you provide an example patch? Wesley stated it wasnt working
      "No there was a big discussion in november and render to texture does not currently work at all. I agree that this (excuse my french) sucks.
      patiently awaiting 1.5.3 wes"
      Apologies for mis-info if it indeed works. id love to get this working.
      v a d e //
      www.vade.info abstrakt.vade.info
    • Wesley Smith
      Jan 24 2006 | 7:25 am
      Yes, the radial blur example works, but I was referring to the @capture attribute of jit.gl.render. The to_texture message isn't very flexible and I find it very cumbersome. Personally, I like to render to a pbuffer. Ideally we could also get textures from the depth buffer as well.
      sorry for any confusion, still waiting for 1.5.3, wes
    • Pierre Alexandre Tremblay
      Jan 24 2006 | 12:08 pm
    • vade
      Jan 24 2006 | 3:42 pm
      !
      duh.
      way to make baby jesus feel like an asshole! I forgot all about that patch. thanks.
      Sorry Wes for spreading mis-info ;)
      v a d e //
      www.vade.info abstrakt.vade.info
    • williamshome
      Jan 25 2006 | 4:35 am
      Thx. I'll try it out.
      by the way, what do you mean getting texture from depth buffer ?
      (^_^) William