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jit.alphablend online refpage

Using the jit.alphablend object

Jit.alphablend allows you to blend two matrices using the alpha plane (plane 0) of the left input as the crossfade mask.

jit.alphablend Tutorials

  • Jitter Tutorial 29: Using the Alpha Channel. Introduces the use of jit.alphablend to composite subtitles generated by jit.lcd onto a movie.
  • ./examples/jitter-examples/gen/ and ./examples/jitter-examples/gen/jit.pix.alphablend.maxpat show how to use gen to create an alphablend.
  • ./examples/jitter-examples/video/keying/dynamic_alpha.maxpat uses 1-plane (black and white) noise to generate a constantly shifting dynamic alpha channel.
  • ./examples/jitter-examples/video/keying/jit-diy-chromakey.maxpat uses jit.alphablend as part of a bake your own chromakey. While this functions much like the jit.chromakey object, it provides an interesting way to interact with the keyer using a multislider as the interface.
  • ./examples/jitter-examples/video/keying/jit.chromakey-3sources.maxpat uses jit.alphablend to do a downstream key after a standard chromakey, allowing 3 sources to be composited at once. Take a look at how the patch manages the in/out names of the different matrices to keep down the CPU cost. Compare with the technique in jit.lumakey-3sources-slower.maxpat.
  • ./examples/jitter-examples/video/keying/jit.lumakey-3sources.maxpat does the same as jit.chromakey-3sources.maxpat, only using luminance.
  • ./examples/jitter-examples/video/keying/jit.lumakey-3sources-slower.maxpat demonstrates how you would perform the same operation without using matrix operator attributes.

jit.alphablend Tips and Workarounds

  • jit.op can be a great way to massage whatever source you are using for the alpha channel.
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  • A common question is how to alphablend OpenGL objects based on the alpha channel of the texture applied to the surface of the object. For this you don't actually need to use jit.alphablend, you pretty much just need to set @blend_enable 1 and @depth_enable 0 for this to work on most any gl object.
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Third-Party Max externals similar to the jit.alphablend object listing for the jit.alphablend object

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Errors or Clarifications

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