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THE ARTIST BETWEEN THE RAYS: Christian Bloch

Christian Bloch is an acclaimed VFX artist, working at EdenFX in Hollywood , California . His work can be seen in StarTrek: Enterprise , Smallville, Invasion, Lost, 24, and a growing number of movies and commercials. He has been a pioneer in the practical application of HDRI in post-production, specifically under the budgetary and time
restraints of TV production. Christian is also the author of the "HDRI Handbook: High Dynamic Range Imaging for Photographers and CG Artists", which has just been released.

The handbook covers a lot of ground (from what I can tell it covers everything), while being an easy and fun read. The book spans the topics of explaining where HDRI comes from and who was involved with it's birth. Bloch covers how this type of imagery relates to the human perception of light and exposure and how HDRI compares Film. The book proceeds to detail out different types of HDR's and their positive and negative attributes. That's only the beginning! The handbook details how to capture HDR images, tonemapping, HDRI processing, stitching, and practical use in both photographic and CGI methodologies and covers ALL of the different type software related to the HDRI process. The book comes with a DVD that includes assets and tools to get you started AND there is also a companion website created for the HDR community called HDRLabs.com.

Lets get to the interview!

MYMR: Christian, perhaps you can tell us how you got started with the HDR Imagery?

Christian: The first time I heard about HDRI was in 2000 at Paul Debevec's show at the FMX conference in Germany . Being a student of Multimedia Technology at that time, I had a pretty good insight in math and image encoding. So it snapped right away: Floating Point is the way to go! It's amazing how a simple tweak on the foundation - the bits and bytes - can twist the entire landscape of digital imaging. All the implications and possibilities made my head swirl.

Around the same time Lightwave was one of the first off-the-shelf renderers that could use HDRIs for lighting. It could also render HDRIs out, and so I started my own experiments right away. First starting off with Debevec's light probes, but quickly tailoring my own ones with a chrome ball and HDR Shop.... Two years later, in 2002, I chose HDRI as the topic of my final diploma thesis. At that time I was already working at EdenFX. They endorsed this R&D, and gave me lots of time to figure out how to streamline the process and make it ready for TV production. And so my project was called "Practical application of HDRI in post-production". It took me about a year to write the thesis, and then it got me the achievement award of the University of Applied Sciences Leipzig . And I guess it also got me a permanent gig at EdenFX.

Currently, HDRI isn't that much of a buzzword in the CG industry anymore. Everything is pretty much daily business. But in photography, there is a strange HDRI mania going around since last year. It's this second rise of HDRI, that will really propel this
technology into the mainstream. And were not just talking about lighting CG objects with stock light probes here, this is HDRI capturing and editing for everyone. This is huge. We're at the dawn of a new era in digital imaging in general.

And so it came that a RockyNook, a publisher that specialized in photography books, read thesis and came up to me "Can we print that?" And I said: "No way - this stuff is 3 years old, and there has so much happened in the meantime, this would need to be rewritten from the ground up." And that's what I ended up doing. I've spent another
full year writing an update, invited 2 professional photographers and one of the best panorama experts to write contributions. And the result is a solid 340 page book, that really sheds light on all aspects of HDRI: the foundation explained in simple language,
shooting tips, panorama stitching, floating point compositing, lighting CG objects.


MYMR: In Chapter 1 of the HDR Handbook you cover the strengths and weaknesses of digital and analog photography and talk about how these types of photography strive to capture what the human eye does. From the digital and analog world HDRI technology was born and is finally mainstream. Where do you see digital imagery going from here?

Christian: Well, first of all - let me clarify: HDRI is a digital technology at its heart. You can use analog sources, but ultimately the HDR image will be living in the digital world.
To be honest, my photography background is pretty fresh, and I have no experience with shooting film whatsoever. As a CG artist I have always been working exclusively with digital imagery. But from what I hear, serious photography has just recently transitioned over to digital. Just now we can reach the quality level known from analog, both in terms of resolution and dynamic range. HDR imaging will take it further from here, leveling up the post-processing opportunities by providing better quality in the source material. It's just the evolution that keeps on going. Images tend to become bigger, already we tinker with Gigapixel images, and ways to make such super-resolution images with regular cameras. And then there is some super-cool technology coming up, where you can refocus a photograph in post. It works by capturing the image not just with one big lens, but rather a field of really tiny lenses. The actual image is then derived through some algorithmic magic, and it looks just like a regular photograph - except for the fact that you have a depth channel, and you can digitally move the focus front to back however you want.

So yeah, the short answer is: digital images will become more information-rich, providing easy access to a lot of post-processing techniques that were formerly known only from science-fiction.

MYMR: In chapter 2 you reveal, compare and contrast different types HDR formats along with compositing packages. From file format to 3d renderer, to compositing package, what would be your ideal CG HDRI pipeline?

Christian: The case of file formats is clear: OpenEXR is the way to go. This is pretty much the only production-ready HDR format, because it can carry layers, extra channels and all kinds of metadata.

As to what specific programs to use - well, that certainly depends on a whole lot of other factors. How familiar that software feels, how much training material you find, what your budget is, what is used in your facility. They're all the same, really, so instead of dictating a CG pipeline I rather show you concepts of how stuff should work and hint at options of how you make it HDR-ready. That's the kind unobtrusive advice you will see all throughout the book. Personally, I prefer using Lightwave with the fabulous EXR Trader plugin (to get channel support), and Fusion 5 for compositing. But if you're using Mentalray or VRay, and After Effects with the ProEXR plugin, that is just as fine.

One application I highly recommend using, and that is Photoshop CS3 Extended, again with the ProEXR plugin to get access to channels and layers in OpenEXR files. There is no better way to edit HDR still images, be it textures, or still renders.



MYMR: Throughout the later chapters you cover in depth, capturing, compiling, tonemapping, processing, shooting panomaric HDRI's, HDRI applications in CG, the list goes on. There are so many practices involved with this field...what is your favorite niche?

Christian: After making CG professionally for 7 years, shooting and stitching panoramic HDRIs is what I find most exciting today. It's just so much more rewarding to create an immersive image, that really resembles a nice location in all it's aspects.


MYMR: What was the most difficult part in putting this book together?

Christian: The writing itself is probably the hardest part. As CG artist my mind tends to wander, and I tend to do a million things at once without really thinking about them. But when you want to put it all down in writing, you have to pick up a logical thread, follow that path, and turn it all into a linear chain of thoughts. It's very difficult, especially with complex subjects like HDRI, where everything seems to be connected. On top of that, English isn't my native tongue, and I am not a big fan of high-flying expert lingo either. So I kind of forced myself to explain everything in simple words in common conversational English, no matter how complicated the subject really is. This is where there is a very fine line to meet between breaking some highly technical information down into something that is easily accessible, and still staying true to the original research papers without grinding them down too much.


Click on Image to go to HDRLabs

MYMR: Please tell us a little bit about HDRLabs.com.

Christian: HDRLabs.com is designed as the companion website to the book. This is kind of a new thing, but it makes so much sense. This way readers have a place to talk about their own experiences with HDRI on the forums. Also, this is such a boiling field right now, that there is new stuff popping up every week. On the front page of HDRLabs.com I
can collect all these news and updates.

During my research I became friends with a lot of fine coders and scripters from all over the world. We started several projects; every time there was something like a gap in the workflow, or one missing puzzle piece in the software landscape. This is how Marc Mehl
started Picturenaut: a state-of-the-art alternative to HDRShop (where development has stalled years ago). This is also how Christian Bauer from CGTechniques.com had the idea for Smart IBL, a platform- independent format for HDRI lighting presets. These were all collaborative projects of HDR enthusiasts like myself, that just happened throughout the years. And they all matured around the same time the book was ready, and so HDRLabs.com is now their permanent home on the web.

MYMR: What are some of the major problems 3D artists come across when trying to light something realistically using HDR photography?

Christian: One that bugs me personally, is that everybody uses the same old stock HDRIs over and over again. Without regard if they actually match the background or not. Guys - just get a Christmas ornament and shoot your own HDR image! It's not hard at all!
The other stereotype of sloppy HDR-lit rendering has a pixelated HDRI shows up as defocused splotches in the background. That always looks like shot with a macro lens and kills the scale - everything looks like a miniature.

On the other hand, using super high-res HDRIs for lighting purpose is overkill. When there is a lot of fine detail, or even the sun showing up in the image, this will get you royal render artifacts. You can brute-force a clean render by ramping up the sampling rays, but then your render will take forever...
However, these are rather visual issues, that most people are just fine with. There are several obvious problems, that are asked over and over again: Why are my HDRIs so dark? Can I change the levels of an HDRI? Why doesn't my panoramic image wrap around the scene correctly? These things that are all very easy to solve with just a basic


understanding of panoramic mapping types and HDR editing in general. Just after skipping through the HDRI Handbook you won't ever ask these kind of questions anymore, because they will feel so obvious.

MYMR: In the past flickering has been a common plague throughout the Mental Ray community when it comes to using HDRI and final gather. Does Smart IBL address this?

Christian: Smart IBL certainly helps reducing artifacts like flickering and sampling noise. That's because the lighting is done with a small blurred environment HDRI. Random sampling rays will more likely hit areas of the same color, there is less of a chance that individual
rays hit a certain bright detail in the map and throw off the balance. This is somewhat like a very generic trick, that works with all renderers - not just a particular Mental Ray thing.

You want to use a low res blurry HDRI as diffuse light. But that looks bad in reflections, so reflections should show a high res HDRI. And you also want a very high res image as camera background. It's literally just a matter of building such a setup with whatever tools a 3d application has to offer. That's the idea behind Smart IBL.

MYMR: How exactly does Smart IBL change the way 3D artists use HDRI to light their scenes?

Christian: Well, if you have never broken out an HDRI this way yourself, you probably just threw it into the environment slot and start tweaking render settings from there. And you fight artifacts while trying to keep render times bearable. With Smart IBL you start with an optimized setup. If you would want to build it by hand, it would probably take you a while figuring out all the slots where to apply the diffuse map, the reflection map, and the background map in your 3d app. It's possible, but its a lot of work. Smart IBL is just a way to automate this. You just run a loader script, and it lists all the lighting sets you have in your collection, and you just pick from there.

MYMR: How difficult is it to learn smart IBL?

Christian: Lighting a scene by applying a lighting set is pretty much self- explaining, I think. Just pick and go. It does help to get familiar with the setup that gets generated, because you will certainly want to tweak it from there.

Making your own lighting set takes a bit more, though. You would have to break out the environment, reflection and background image from the original HDRI. This used to be pretty tedious, until Chris Huf joined the project and wrote sIBL-Edit. It's a standalone application that can do all that very easy for you - including hardcore image edits like applying a spherical blur to the environment map and show HDR Histograms. It even has a built-in picker for the sunlight position and color. Importer scripts will then know where to put the keylight so it matches the environment.


Click on Image to visit smart IBL

MYMR: How long did it take to develop Smart IBL?

Christian: Christian Bauer (from CGTechniques.com) came up with the original idea way back, in 2003. We have just done a pretty cool project together, the HDRI Apartment Challenge. That was my living room table with a bunch of virtual objects on it, that was rendered by hundreds of people in all kinds of software. And this was when we figured out how each software can basically deal with HDRI. But to get the most out of it, you would need a better setup. Which turned out to be very similar, with the same ingredients just applied differently. Christian was coding a MAXScipt, and I made an Lightwave LScript. About a year later Volker Heisterberg from the Filmakademie Baden- Wuertemberg made the MAYA implementation in MEL, and at some point Katachi had started to make a script for Cinema4d. We pitched all that as a sketch for Siggraph 2004.
When that was rejected, we all kind of lost interest and forgot about it for a year. It still had made its round in the German Lightwave community (because I tend to use the folks at Rendering.de as BETA-testers), and then all the sudden Chris Huf made this great sIBL-Edit. This kind of revived it all, because NOW that you could make the presets so easily, it actually felt like it made sense to go through Smart IBL.

MYMR: There is a tools section in hdrlabs.com, what tools do use specifically use to get your HDRI's ready to go before using smart IBL?

Christian: Well, wouldn't put a tool up there if I hadn't used it. This is the whole point of a moderated list like this. My personal favorites are Photoshop, PTGui Pro, Picturenaut, Photomatix, and FDR Tools.

MYMR: What are your hopes for hdrlabs?

Christian: It would be great to see people from all kinds of different fields come together and share experiences. Photographers, Compositors, Panorama Photographers, CG Artists - they all approach HDRI from a different perspective. I believe each group can learn a lot from each other. Ideally, some cracks would come together and start an interdisciplinary project.

MYMR: Christian thank you for your time. Where can people go to find out more about you and your work?

Christian: I suggest you head over to Amazon.com and get my book. Or even better
- go to www.HDRLabs.com and click he Amazon link in the sidebar :)