This year at Libreplanet I gave a small talk about Python in Blender. My primary goal behind was to talk about the ways that Blender, by exposing its Python API directly in the interface, there for users to discover, gives a new meaning to ‘free software’ not just in licensing or community (though these things are important) but also in the design of the program itself. How many programs do you know that have an ‘edit source’ button for each interface element?
One of the elements of the talk was a tutorial on how to use Blender’s Python API, and add a new primitive type into the Add Mesh menu. This is made very easy thanks to the template scripts included in Blender, that allow you to create your own with just a few edits, and by the fact that you can grab data from Blender, and pipe it into your script directly.
I’m not sure if the video from the conference will be available from the FSF; they are slowly putting talks up on the FSF mediagoblin site – I’ll post something if it does. In the meantime, I recorded a Python tutorial for just this part:
Going back and recording the tutorial actually made it better than what I presented at the conference. I used the Addon template, instead of the Operator template, which makes it even easier to share the code. Interestingly, during the presentation, I found a bug in the operator template, which I fixed after it was over. The fix is now in Blender 2.77, a nice way in which a presentation about a free software project leads directly to a contribution 😉
We’ll try to do a bi-weekly installement of Addons for Empathy (until we run out of addons). This one is a two-parter: Our main installment is about working with proxies in Blender, the second is about a bold new experiment in Rig UI.
The video is about two addons, both making proxy editing in the sequencer more friendly to our project. A quick explanation:
Blender’s Video Sequence Editor or VSE for short has a feature called proxies. This basically allows an in-place replacement of strips by 25%, 50%, 75% or 100% versions, in a fast format (.jpg or motion jpg) This is especially useful when:
Editing Large format files that are too slow to be realtime – either in resolution (2K or 4K) or in type (.EXR!!!)
Editing over the network, especially files of the previous types
Working with complex and multiple effects that could be benefit from being cached
So Proxies in Blender work a bit like a combination of proxies and caches. I prefer them as the former, since it skips having to recalculate every single you change some timing – instead they only need to be recalculated when the sources change.
However, working with proxies in Blender can be painful by default, and this is where Proxy Workflow Addon comes in:
Editing Proxy settings must be done strip by strip: Proxy Workflow lets you set them for all selected strips at once
Default location is in the same folder as the originals, which is bad in the case of network shares; Proxy Workflow automatically sets them to a local directory “TProxy” that contains all the proxies for the edit, and can be moved around like a scratch disk
Sometimes Blender tries looking for the original files even when it is using proxies. If you are trying to use proxies to avoid using the network/internet, this becomes a problem. Proxy workflow allows ‘Offlining’ strips, and then ‘Onlining’ them again when you can reconnect to the network
Blender doesn’t know when the source files are ‘stale’ and need to be re-proxied – for instance if you rerender. Proxy workflow timestamps as it makes proxies, allowing you to select a bunch of strips and re-proxify only the changed ones.
Proxy workflow is designed to work with movies and image strips only for now, as I’m interested in true proxies, not caching effects.
A seperate addon is called ‘Transparent Proxies’ and does what it says on the tin (and no more): It allows making proxies of image sequences that preserve the alpha channel for alpha over effects. It does this by cheating: It uses Imagemagick on the commandline to make a .tga proxy, and just renames to .jpg to satisfy Blender. You need to install imagemagick first for it to work.
Â Bonus: Rig UI Experiment:
Code is at gitorious
This brings us to the bonus round- the Rig Selection UI. I’m continuing my round of experimentation with BGL and modal addons, to make the kind of ‘typical’ rig ui where animators can select or act on a rig by clicking on an image. This ui is using an SVG file to define the hotspots, and a PNG to actually draw the image. It already works, though I’m still going to refine it and add more options/ easier rig customizability. The end goal is to be able to do Rig UIs without writing code, simply by drawing them in Inkscape and pressing a few buttons in Blender. Stay tuned!!!
Hello all, long time no post!
As we’re getting closer and closer to releasing our files, I’m noticing that we have a huge (and I mean huge) trove of Python code that is largely undocumented. Some of it is pretty specific to this project, And other bits are useful in general. Even the specific stuff could be adapted, so it’s worth going over.
To address this we’ve thought of doing an ‘Addons for Empathy’ video series, quickly explaining what some of the addons do, in addition to more traditional docs. The first I’ll do in this way is the Floating Sliders Addon: In short, this pops up small, keyframable Open GL sliders for any Floating point Pose-bone properties. The code is on gitorious, and following is a simple video explanation of what it does and how to use it:
As always, the video is licensed CC-BY, while the addon itself is GPL.
You can also download this video as a high resolution .webm or .mp4 file, or watch it on youtube
The screencast itself was edited in Pitivi, with Inkscape titles. Video was captured via the Gnome screencast feature, and audio with Audacity
Big thanks to Campbell Barton for help getting min/max of custom properties, and explaining some of the finer points of keymaps, and to Dalai Felinto for showing a possible hack to make a popup menu (I ended up using a slightly different way)