Saving Renders in Blender So You Can Finish Composition Later
How many times have you dreaded the render time before finally doing the composition for a piece? So many people say, “Just save the image, and open them in the compositor later”, but what if you have multiple passes, multiple layers, and object/material passes you want to take advantage of? Well, a PNG or JPEG isn’t going to give you that option at all. So, you’re probably like me, you wake up start the render right away, and hope it’s done after you finished waking up. Well, at least that’s how I use to be, but not anymore. Instead I take my time waking up, then do my composition with everything available. Ready to find out how?
So the not-so-very-secretive secret, is to use OpenEXR to save your renders. Specifically the option to save in Multi-Layer mode. You do this just like you save it as any other file type, except you choose to save it as “OpenEXR MultiLayer”, (Use the codec Blender defaults to. It’s intuitive like that). Once you have this file saved, you can close Blender, turn off your system, and be happy to know you can do your compositing in the morning. Ok, off to bed before we stay up until 3am tweaking compositor nodes. Seriously, this happens a lot.
So come the next morning, fueled by coffee, and whatever else, it’s time to composite. Open Blender, as well as your project. Of course you don’t have a Render Result, so in the UV/Image Editor, open the newly saved OpenEXR…. you know what, I’m sick of typing that over and over, let’s just call it the “Layer File”, cool? Ok, open the Layer File. So now you have that in your list of files. Now go to the Node Editor, or the Compositing Screen Layout, and create a new Image Input Node. Next to the open button, click the image list button, and choose your Layer File name (filename.exr). When you open it this way, you’ll notice the “Layer” option is set to Combined. Switch that to “RenderLayers”, or if you have multiple layers, pick one, duplicate the node, and choose another layer. Rinse and repeat until you have all of your render layers available. Now, enjoy as you see all of your passes just like it was a Render Layer input. While you’re here, check out that screenshot I took over there -> where you can see both types of input nodes next to each other. You’re not losing a single thing, except that some are named a little different, and the feeling that you don’t have without a fresh Render Result.
Moving on! Let’s take a look at a few things, as the Layer File does not work exactly like the Render Layers. One very awesome feature of the Layer File, is that when you open the file in UV/Image Editor you’ll notice that you can look at each pass! Normally, you would have to connect it directly into the viewer node, but not anymore. If you haven’t noticed already, the “depth” pass is all white. Just like the Z-depth pass, you need to use a normalize node first.
Now that we have everything ready to composite, we need to set it up to view. If you haven’t noticed already, you are probably looking at a “combined” render result, which doesn’t do anything but look at your saved Layer File image. Just like the image input node, change this to your RenderLayers, or Render Layer you want to view.
Lastly, you might be wondering, “Can I actually view my full render, or what? I have my output plugged into the composite, and viewer outputs, but my image editor isn’t showing anything with the Render Result, or Combined. You tricked me, this doesn’t work!”. You’re right! Hahaha. Trollolololol-lolo-lol.
I thought the same thing for a minute, and then realized that my “Render Result” option had mysteriously vanished when it wasn’t being used. The answer to this issue, is to actually switch to a different view. Specifically, the Viewer Node result.
Of course, if you feel the need to render a new result, because you changed the scene, make sure that both the RenderLayers node exists, as well as the composite node for later. If you don’t have the RenderLayers input, you’ll find that your renders go very quick, because they are only rendering the composite data.
So once you have all of that taken care of, then you have probably realized that using OpenEXR Multi-layer files is so much nicer than having to deal with the quirky Render Result, and never have to re-render. Not only that, it makes for a good practice of saving different renders, and passes to compare with. I can honestly tell you this is how I will continue to save renders for compositing, because let’s face it, OpenEXR Multi-Layer files work great. I don’t lose any of the features I would have with a render, and I don’t feel rushed to finish compositing before I quit Blender.