Know Your Devs – Ondra Karlik

With Corona Renderer, you don’t just get the software, you also get the team behind it. Using the software will teach you about that, but how do you get to know about the team?

That question gave us a new idea, “Know Your Devs”, where we invite users to post their questions for a particular developer, starting with… Ondra Karlik!

Ondra Karlik

Read Ondra’s answers!


Corona Renderer Know Your Devs, Ondra Karlik


Work-life balance questions

How did you manage to keep a social or family life before the official Corona release – I’m talking about the hard work of coding.

Easy, I did not have any social life ;). We just locked ourselves in a room until Corona Renderer 1.0 was out. It wasn’t pretty, but it got the job done.

Corona 1.0 Life
Work , live, eat and sleep, all  in the offices while working on Corona 1.0

Later (since around 2016), I gradually restored a more sane balance when we hired more people and I did not have to work such long hours to fix everything that was in flames at any given moment. Right now, I am working sensible hours again.


What is your work life balance like?  Do you work 8 hr days? 10? What about on weekends?

In 2014-2015, around the Corona 1.0 release, I was working pretty much non-stop. Sometimes it was fun, sometimes not, depending mostly on what I was dealing with – for example website and licensing code was no fun at all for me, but I always enjoyed adding new features, even if it was Sunday 😉

Corona 1.0 Life, celebration meal
The celebration meal after the launch of Corona 1.0

Right now, I am trying to work more reasonable and sustainable hours – a standard 8 hours per day, with free weekends. But sometimes it is hard not to think about programming on weekends 😉


Corona history

How did you get the idea to develop a new render engine ?

I was in college in 2009, and I had to pick a topic for my bachelor thesis. I had an agreement with a faculty member to create a web timetable for the school, but he stopped responding to my emails. I had about a week to find another topic. A friend suggested I do a renderer. I first thought it would be too hard, but he convinced me to try it.

Corona 2009
A VERY early test, from Corona in 2009…..
Daniel Craig by Luc Bégin
.. and Corona Renderer today (Daniel Craig, by senior character artist, Luc Bégin)


I am very happy about it, but why did you choose 3ds Max as the main platform for your render?

It was natural decision, since I was already a 3ds Max user – I learned it while in high school. Knowing the software from a  user perspective was immensely helpful, and was a key element in Corona’s success.


What led you to believe that you could build a new render engine that could compete with the giants? I’m interested in the specific gap you saw, and why you felt confident that you could fill that gap? In other words, what did you know that nobody else knew?

I did not see any gap ;). At first I was working on Corona only as a school project, with extra stuff (such as 3ds Max integration and global illumination) added because I wanted to try implementing it, mostly just as a technical challenge/programming exercise. I was using V-Ray 1.5 for a few years and I considered it good enough, without any need for improvement.

I started posting images to a Czech online forum and soon a few people wanted to try it, with one (Ludvík Koutný) being so dissatisfied with Mental Ray, that he wanted to replace it with Corona Renderer.

Glossy Interior, by Ludvík Koutný, from Ondra's Master's thesis in 2011
Glossy Interior, by Ludvík Koutný, from Ondra’s Master’s thesis in 2011…


… and a recent video from Ludvik Koutný, using Corona Renderer

This sounded unreal to me at first, but I accepted it as a challenge – make Corona Renderer good enough to be used in production. It took another year or two, but to my surprise I found out that I could actually improve upon the current state-of-the-art.


Random questions

I’ll keep it simple – favorite type of coffee? (beans, prep method, or anything related)

I started drinking coffee late (only in 2014), to keep going when finishing the Corona Renderer 1.0 release. Since then, I quickly settled on Italian style, strong espresso.


Did you get rich from selling Corona to Chaos Group???? 🙂

Yes 😉

"Black And Gold" by Eduard Caliman
This is not Ondra’s house – it’s “Black And Gold” by Eduard Caliman


Everyone knows Corona Renderer is beloved by people in Archviz. And in other familiar fields as well, of course. But what do you imagine is the most eccentric use of the renderer?

We have seen quite a few eccentric uses for Corona Renderer! It was used in quite a few research papers (both by our team and by other researchers). There is some fractal art created with it (and people claiming they found hidden symbols inside the fractals). One guy claims he uses Corona to unify the theory of electromagnetism with the theory of gravitation.

"Rated R", by Alejandro Rivers
Corona Renderer – it’s not just for arch-viz (image “Rated R”, by Alejandro Rivers)

We had to delete some pretty convincing renders of male genitalia made with Corona Renderer from our forum. And there were lots of other projects, from military planning projects to religious education materials – so the question would be easier if asking what Corona Renderer has NOT been used for!

And let’s not forget the Corona Benchmark, used by hardware builders and reviewers!


Favorite movies!

I will skip the movies everyone likes (yes, I like Lord of the Rings and Star Wars 😉 ) and call out some less well-known ones… for thrillers, I would mention Scarface, Pi, V for Vendetta, American Psycho. When it comes to comedy, I love the old school parodies such as Hot Shots and Spaceballs.

Oh, and I hate the current superhero movies trend. Can’t wait until it is over 😉


Ondra, tell us something about your hobbies & routines (non-coding).. who knows, maybe you’re a guitarist like TomG 😉

Corona IS my hobby! Other than that, my hobbies are pretty dull – tourism, cooking, computer games, watching internet drama, … Tom actually gave us a guitar when he visited the Prague office. I want to learn how to play one, but I will have to get a left-handed one first… and also get some free time 😉

Table football at a Corona Academy
Table football at a Corona Academy


What is your ultimate goal, personally?

Well, for long time, it was to make Corona Renderer the leading arch-viz renderer. I am doing some thinking where to go from here, currently.

Ondra Karlik


We hope you enjoyed this first “Know Your Devs” – be sure to sign up on the Corona forums to watch for the next one, so you can interrogate the next developer who takes the hot seat!

15 thoughts on “Know Your Devs – Ondra Karlik

    1. Thanks Mihajlo! We hope it will provide a different kind of insight to the software and the company – and that it gives people a bit of a laugh (or smile at least) as well as being informative 🙂

    1. Everyone seems to have enjoyed this, so we will definitely be letting users interrogate… err, I mean, ask questions to other developers in the future 🙂 Thanks

  1. uso o Vray para C4D a muito tempo e ao testar o Corona eu simplesmente voltei a amar a trabalhar com 3D. porém depois da venda para a Chaous Group estou com receio do Corona parar no tempo.

  2. It’s perfectly possible to learn to play the guitar as a leftie on a right-handed guit, Ondra. It’s a bit different but that’s how I do it 😉

    Thanks for the nice read!

  3. Well, He deserves this “Yes”! But I am afraid selling its own child will give him sad memories through his entire life. The product is unique, as he is. True master!

    1. Do keep in mind that it’s actually more “received investment in our child” rather than selling our child 🙂 As noted in the original article about the merger, a very long time was spent agreeing the terms under which it happened, which is why the development teams remain separate etc. And that means Corona Renderer continues to be developed just as it was before (only we have more money invested in us, so we can do more!) and so it remains as unique as it ever was 🙂

  4. (quote)one (Ludvík Koutný) being so dissatisfied with Mental Ray(/quote)

    To funny, Ludvik being dissatisfied with Mental ray, I remember those days well

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