Rendering out a composited image or sequence

Hi. This is just a quick question.

Is it possible to composite a previously rendered image in blender without re-rendering it? That is outputting the composite without re-rendering the 3d viewport?

Can’t figure out how to. Any one?

You’ll only have as much information to work with as the rendered image format can hold. For .png for example you have an alpha channel that .jpg can’t

If you save your render as an OpenEXR Multilayer format you’ll still have all the render passes available to you in that image.

Load previously rendered images with the Image input node

Hi. Thanks for the reply.
There should be something more to what you said because I have loaded the images with the input node.
I am also adding an output node. Trouble is, it is going through the view-port rendering process again.
Where it should just composite the images I loaded in and render them out.

I am only using the rendered image, no passes. I have them rendered out in a .png sequence.

I am missing something here, I know. Just can’t figure it out. Someone help.


Render your stuff to image sequences. Then read them in in compositor (remove RenderLayer input nodes if you need nothing from 3D scene) and do your stuff. Write result as usual using output settings in render panel or FileOutput node.

As Richard noted, use a suitable format for saving your 3D elements so that you do not lose information that you might need (color precision, alpha, z pass etc). EXR is usually the most foolproof choice although a bit heavy for simple tasks.

Delete the Render Layers input node to prevent it rendering the camera view.

And that’s how it is done. Little things. :smiley:
Thanks man.

It’s best practice to seperate your compositing scene from the 3D scene if possible, as you can end up with memory handling or cache issues too.

I definitely suggest the MultiLayer OpenEXR format. “Heavy” or not, it is designed expressly for this purpose. It keeps all of the separate layers of digital information, in floating-point numeric format, with no loss. “So what if it’s phat?”