Slab Help!!!


    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...

    • 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.
    • 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
    • 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
    • Jan 24 2006 | 5:52 am
      I see.
      But why would the example "jit.gl.render.radialblur" still manage to use
      it ?
      (^_^)
      William
    • Jan 24 2006 | 6:15 am
      I am using to_texture regularly. The destination context size must
      match the texture size exactly.
      -Randy
    • 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
    • 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
    • Jan 24 2006 | 12:08 pm
    • 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
    • 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