Photoshop-style composite blending between multiple videoplanes


    Aug 12 2011 | 8:49 pm
    Hi,
    I'm looking for a way to get all the Photoshop-style blend modes between multiple videoplanes. To be clear, I know how to use a slab to blend two sources onto a single videoplane via co.%s.jxs... but I want to use similar blend effects between images that are being rendered to different videoplanes.
    I've read tons of posts that talk about using the blend_mode attribute of videoplanes (with @blend_enable 1 and @depth_enable 0). Experimentation seems to yield a few Photoshop-like modes, but so far I haven't been able to get close to the full complement. Slab compositing doesn't seem to be a solution since it appears to work only with multiple inputs and rendering to a single vidplane. I get some additional blends by putting jit.op or jit.gl.slab with op.%s.jxs between the matrix/movie sources and their respective videoplanes, but the possible combos of all the ops and videoplane blend_modes yields a daunting number of possibilities... and I'm still not convinced I'm on the right path to finding all the blends. In a perfect world, I'd also like to use alpha channels in this same blend/compositing process.
    Any help is greatly appreciated!
    Thanks,
    Jeff

    • Aug 15 2011 | 11:50 pm
      Tap, tap... is this thing on? ;)
    • Aug 16 2011 | 6:42 pm
      you seem to be on the right path. there is a limit to the number of photoshop style blend modes you will be able to achieve with fixed function. here's a start: add: blend_mode[0] = 1; blend_mode[1] = 1;
      multiply: blend_mode[0] = 2; blend_mode[1] = 0;
      screen: blend_mode[0] = 4; blend_mode[1] = 1;
      exclusion: blend_mode[0] = 4; blend_mode[1] = 5;
      colorblend: blend_mode[0] = 3; blend_mode[1] = 4;
      alphablend: blend_mode[0] = 6; blend_mode[1] = 7;
      coloradd: blend_mode[0] = 3; blend_mode[1] = 1;
      alphaadd: blend_mode[0] = 6; blend_mode[1] = 1;
      beyond that, you must get in to shaders. this link should help http://mouaif.wordpress.com/2009/01/05/photoshop-math-with-glsl-shaders/
    • Aug 20 2011 | 12:22 am
      Thanks so much, Robert!
      I've not delved into creating my own shaders yet... perhaps this is the impetus. Quick question before I jump in off the high dive: The reason I'm not using the existing shaders like co.difference.jxs is that this family of shaders appears to require two inputs. I'm envisioning that I need shaders that use only one source/input on a slab for a single texture/videoplane... and that construct per videoplane will allow discrete control over layer blends a la Photoshop layer blends, right? Or am I missing a fundamental concept? ;)
      I'd be eternally grateful if anybody wants to provide input/models/examples on how to turn the photoshop-math-with-glsl-shaders code into jitter-ready shaders.
      Peace,
      Jeff