Matt Ebb

Today I finally got around to fixing Blender’s weird camera to more closely resemble real-world counterparts. Previously Blender’s camera was hardcoded to use a sensor aperture width of 32mm, which doesn’t reflect any commonly available real-world camera sensor/film size. In turn, this meant the focal length (mm) for the lens didn’t resemble any real-world lenses whatsoever. It was pretty misleading when trying to intuitively choose lenses based on photographic experience, and also makes it a lot harder to match live-action footage.

I’ve made a patch to allow specifying a sensor size, along with a handful of common presets – easy to add some more. This first version isn’t 100% correct in that it doesn’t modify the FOV due to focus (in reality, the extension of the lens elements due to focusing slightly alters the FOV), but this can be added pretty easily as an option later. It’s also deriving the apparent FOV purely based on the horizontal aperture width, options for vertical/diagonal may be possible to add later, but would need to check how the renderer works with varying frame resolution aspect ratios.

I thought it would be fun to do some real-world tests, so I quickly set up a very rough set in my backyard to see if a virtual set in Blender would match up. The setup and measurements were very very dodgy and I didn’t expect it to match perfectly. I shot with two cameras – first a 5D Mk II with a 12-24mm on 24mm and a 24-70mm on 70mm. To compound the un-scientific sketchiness of the test even further I tried again with my 6×6 Mamiya C330f TLR with 65mm and 80mm lenses, using a compact digital camera shooting the ground glass focusing screen (yes, too cheap to spend film on this). Given all this, I was pretty surprised to see that with a bit of tweaking it looks like it’s doing the right thing.

Anyway, the patch is up on the blender patch tracker, would be good to get some testing first before trying to commit, especially since I’m not sure how it should interact with the game engine either.

As of last week, I’ve decided it’s time to finish up with my full time Blender development contract and move on to new things. It’s been 8 months now since I started with this, pretty close to the first 9 month target/budget, so it’s not too unexpected. I’m happy to have done my part in bringing Blender 2.5 closer up to production ready status over the last several months, and this decision doesn’t necessarily mean I’ll cease contributing, but it will be the end of it for now in this professional capacity. It’s been an interesting time, I’ve had some new experiences, but it’s not what I really want to be doing with myself in the long term – I’m itching to get back into more regular creative production work!

I think what I’ve learned from this is that while some people are happy programming for programming’s sake, It’s really most interesting for me when it’s directly in service of some artistic goal or creative problem to solve. While I’ve done the work to the best of my professional ability, the last several months of report management and bug fixing (I estimate about ~350 fixed since the start) has been a bit motivationally draining, so it’s a good time for change.

So, what next? I’m looking forward to getting stuck into more freelance work again

(hire me! 😉 as well as developing some new skills in other areas and working on some personal projects. Hopefully more interesting times ahead!

For a little while now I’ve been working in my own time on a renderman connection for Blender 2.5. The new render API, while not fully complete and stable, makes it much easier to connect Blender’s scene data to external renderers, via python.

I’m aware that other people are interested in this topic too, but so far I’ve been doing this for my own use – to get more familiar and experienced with renderman in practice (by diving deeper in head first), and to develop something I’d like to use myself as a lighting/shading artist. I’m also concentrating on the 3Delight renderer at the moment, since it interests me most and provides a free single license.

It’s still quite a work-in-progress, and by no means provides exhaustive support at this point. I’m tackling this from a pragmatic angle, with the priority of implementing things I want to use myself first and making that easy to use rather than trying to supporting the entire rispec from the start. I’ll probably release the code very soon, but I would like to clean it up a little bit first.

Here’s a test I rendered out last night, with a model by my mate Tristan Lock:

Anyway, currently it supports: polygon mesh, subdivision surfaces, uv coordinates, depth of field blur, motion blur, surface/displacement/lightsource shaders with parameters available in blender material properties, simple conversion from blender’s lamps to renderman lightsources, shadow maps, raytraced shadows, built-in indirect lighting and environment lighting using 3Delight’s ‘indirectlight’ and ‘envlight2’ shaders, and shader editing and compilation from the blender text editor.

Here’s a quick screencast showing how to use the voxel data texture to load and render image slices as 3D volumes. It may be a little unclear in this small window, but you can click through to Vimeo to see the HD/fullscreen version. This is using the sim_physics branch in blender SVN, you may be able to find builds for your system on graphicall.org.

Today I committed some new additions to the blender sim_physics branch, making it easier to load up different types of voxel data sets for volume rendering within Blender. The most significant addition is a new ‘Image Sequence’ file format choice in the voxel data texture, which makes it easy to load up image slice sequences as the Z axis of a 3d voxel grid.

There are some other new features and optimisations mentioned in the commit log too. I really hope this helps people involved in medical visualisation/research, if only by providing them a free method for making animations with case data. If you are in the field, I’d love to hear from you.

Some test renders: