Why Render Animations Out as OpenEXR?
February 5th, 2008
We switched to OpenEXR awhile ago (I explained why in this article in February, 2007). How has it helped us and how can it help you?
Let’s start with the “how.” Many 3D programs will render out as an EXR format. We use modo for most of our virtual set design. In fact, we use modo pretty much for everything.
modo is an incredible program. It’s rendering engine is simple, powerful, fast and very realistic. This is a huge plus for us because we don’t have to worry about specific details. We set up a scene and render it.
Shown is a sample virtual set that I personally created from scratch in modo.
I created this prior to the greenscreen shoot so that during the shoot, we could mimic the lighting in the set. However, after the shoot, I go in and tweak the set. If we do a moving camera, I do a camera track so that the set and the talent move together.
Then the elements are ‘glued’ together in a compositing program. Apple’s Shake is used for most of the compositing at Reels in Motion. When the rendered EXR images of the set are loaded into Shake, I can tweak the exposure, making the set lighter and darker just by sliding a bar back and forth.
This way I can better match the talent with the set.
Additional elements can be saved in the OpenEXR file as well, such as alpha channels and shadow information. I normally save these out as separate files, though, as needed.
If you use modo like we do, it is fairly easy to render out the additional files. I’ll probably post a tutorial just on this in the future.
The other nice thing about EXR and 3D renders is it helps even going the other direction.
When on a shoot, I’ll grab my digital SLR camera and shoot several pictures of the set at a number of exposures. Then, in Photoshop, I’ll combine all these images into one panoramic image that contains all the exposure settings so the photograph itself can be ‘re-exposed.’ Normally, these are saved as what is called an HDR image. However, EXR works almost as well.
This image is then loaded into the virtual set’s environment and ‘wrapped’ around the set that you are about to render. This image is then set to be the actual light.
The result is that your render will have all the lights coming from the right direction, including even the minute colored light reflected from the ground, walls and any other subtle nuances.
The final rendered image will then blend with your talent much better and you’ll have a much more convincing image.
Categories: Tutorials | Tags: , animation, modo, openexr, render | No Comments
