Blender Render with occlusion masks as Alpha


Here’s yet another tutorial on Blender to EIAS integration.

So now that you’ve figured out cool stuff like liquids and particles and soft blobby things crashing into each other, you want to use them with other elements that you’d much rather use EIAS for due to it’s simplicity and super fast rendering. One thing you’ll need to do is render the particles (or whatever) in blender and have them disappear behind an object that you’ll be rendering with EIAS. So that non particle object needs to basically become an alpha channel hole in the render. Well I finally figured it out…it wasn’t something that I could find by searching through all the various documentation available on the web, so I stumbled upon it while trying to figure out something else.

In the objects material tab there is a button called ENV. That’s the magic button that was hiding in plain sight. Enable that for each object that you want to be an occlusion mask (I think that is the proper term.)

Then go to the render tab and enable the key button. This will make the alpha that is rendered ‘straight’. (if it’s a glowing object you may want to enable the Premul button instead)

Then render out your scene.

Then render out the EIAS scene.

When you go to composite them all together, make sure the alpha channels of layers that are involved are set to ‘straight’. (unless there’s glowing or fading transparent edges or things like that)

Then apply the mask choker effect with a -.9 setting, this will close the tiny gap between objects due the edge pixels of each layer being slightly transparent so that you can see the background ever so slightly through the layers.

If anyone knows a way to fix that issue without the mask choker, please let us all know…

As for rendering with Blender. There’s no network rendering available unless you can delve into the inky depths of command line stuff (I think…) But everything is included in a blend file except the particle and liquids cache and I’m not yet sure if texture maps are included in there or not. But this makes it pretty easy to move the files to all your render machines and just set the scene to render out a frame range of the entire animation. Not bad considering the price…

As for Multilayer output…you have to get a $95 ProEXR plug-in to have After Effects read all the layers in the EXR files, or you can use Blender’s internal node based compositor to read and tweak them…I haven’t explored the full functionality of that yet, but when I do I will post it here…



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