luma to aplha in gl land

lee wang's icon

hello jitter pros,

i am trying to generate an alpha mask from an greyscale movie
and i want to blend it.

white should be opaque, black should be black.

it should look like, if i use the blendmode 0 3 (which is multiply)
but in this blend_mode, i can not blend anymore.

if i use blend_mode 6 7 and the "co.lumakey.jxs" shader, i can blend, but the keyed greys are looking bright.

is there an other solution
perhabs a lumakey shader with shader with multiply blend_mode ?

l

Max Patch
Copy patch and select New From Clipboard in Max.

here is my demo patch:

Luke Woodbury's icon

You just need '@depth_enable 0' on your videoplane and it should work.

lee wang's icon

hello luke,

thanks for the answer.
depth_enable 0 is not the problem.
it only helps with the max6 versus max5 incompatibility.
i have attached a patch, which should work on both versions.

to see the difference, click on the "blend_mode 6 7" and the "blend_mode 0 3" button.

Max Patch
Copy patch and select New From Clipboard in Max.

best,
l

Luke Woodbury's icon

OK, there is no difference for me between the blend modes, your patch seems to work as I would expect.

Luke Woodbury's icon

Anyways, the help patch for composite shaders should help you:

Max6/examples/jitter-examples/render/slab-helpers/composite.shaders-help.maxpat

lee wang's icon

strange,

an my machine the "blend_mode 0 3" is much darker "blend_mode 6 7"
i am on mac osx 10.6.8, MacBookPro8,2 with AMD Radeon HD 6750M gpu.
max5.1.9 and max6.0.4

perhaps someone else can reproduce ...

best,
l.

Luke Woodbury's icon
Max Patch
Copy patch and select New From Clipboard in Max.

OK, sorry, I can see the difference now, but it does look slight on my display. Does this help:

lee wang's icon

hello luke,

thank you very much for looking into my patch and wast your time ;-)

mixing the 2 layers with a shader is not an option for me.
i am working on a very big patch, which has to be finished the next days.

btw
the co.subtractive.jxs shader is boosting the colors.

i am searching for possibility to create a neutral mask from a greyscale movie. (like the blend_mode 0 3")

best,
l.