Automotive Caustics - Lux + Cycles

After posting this I updated the look a bit. This is the latest version of the image ^^

I recently started playing around with Lux Core Render as I wanted to be able to render nice caustics inside Blender. The results were pretty nice considering the render time and well… Now I gotta say. I am a Lux fan.

However, I still wanted to be able to use Cycles for the main pass. The workaround was to render with Lux in a duplicate scene. In Lux I set the settings to 100% Light Rays so no camera rays were traced, but only light rays. This turned out to work pretty flawlessly and in around 2 min I got these pretty nice-looking caustics.

For this example I bumped the caustics up to 11, just to test it out - And because NOW I CAN FINALLY RENDER CAUSTICS!! But I know this is obviously way over the top.

Thanks for checking out the RnD project!
Happy blendin’ everybody.


This is a very good output considering you are starting with Luxcore. Can’t wait to see another one.
Keep up the great work !


very impressive

Thank you! I will definitely use Lux Core more in the future - Especially in a hybrid manner like here! I am planning on using it to render similar caustics in an animation soon, so I hope this method will work well for animations as well.


Thanks! Glad you liked it

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Yes light traced caustics are animation capable.
Only caustics cache can change between frames.

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Very Interesting, thanks! - Makes sense the cache could introduce flickering. The entire thing with PhotonGI and Light Cache is something I am not used to as I have only used Cycles and Octane (And a bit of vray) before.
I heard other people explaining that you needed to use the Bidirectional engine to render caustics, but I found the normal path tracer does just as good of a job and it feels cleaner. Is the way they calculate the caustics the same or are they approaching it differently?

The things people are talking about with Bidir is just outdated knowledge from the Old Luxrender.
Now for Path tracer + light tracing outperform Bidir in caustic.
Also Bidir isn’t able to render SDS caustics ( Pool caustic / or caustic seen throught a mirror).
path tracer can do it with Caustic cache enable.(but caustic cache introduce flickering when animated) so it is good for still.

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This is beautiful render man, keep it up

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I see, I will stick to the Path tracer then! Thank you so much for the explanation. I couldn’t really wrap my head around it and I was wondering if the path tracer + light tracing was faking the caustics somehow and that was why it could render it so quickly.

Thank you :smile:

Yes of course path tracing + light tracing is totally unbiased. It is fast because it has been tailored for that caustics feature only and use your CPU for that(as much CPU power you give because you can still manage how much computing power to apply to caustic wit the slider) while your GPU are doing the usual diffuse path tracing stuff.

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I featured you on BlenderNation, have a great weekend!


Thank you Bart!!

I doubt you would be disappointed if you just went full Lux… its considered the more beautiful & realistic renderer by many of those who make the comparison!


Yeah, that might be true. I love the idea of having the halt options for rendering - And so many other features feel very thought through. I did feel like it was slower than cycles though, but I will definitely be playing more around with it in the future!

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I did a little relighting of the car - And a new background. Still using Lux for the caustics, but they are more subtle this time, heheh…

I did the relight because I was working on a tutorial about how to use HDR Light Studio in Blender - Link’s here if you are interested! :smiley: