I’ve been testing LuxCoreRender recently and I’m really impressed on how well it handles caustics. The scene is entirely illuminated with light refracted trough glass, which is quite impressive!

Due to its unbiased nature the final render was quite slow, I set the timer for 2h. The denoising algorithm does a great job so I think I could render the final image in much less time. Previewing was quite fast due to the denoiser and the amazing bidirectional path tracing algorithm, so it was surprisingly easy to work with consider the complexity of the calculations.

Hope you like it :3


looks amazing - would be interesting to know how cycles handles this.

Did you use the Path engine with light tracing on or did you use the Bidirectional Engine? Have you set the adaptivity to a higher value like 0.90, it can help reduce render times.


Since cycles is a pure path tracing engine it doesn’t perform well on these kind of problems. I did a quick test and this is what I got, the first one is a standard glass material, and the second one is the Prism Glass shader that I bought some while ago (non pbr). Its not really possible to get a good result without faking it.


I used the Bidirectional Engine, I haven’t really done much research about the settings so thanks! I’ll do a test on it later :slight_smile:

1 Like

That is an awesome result and experiment. But should be a lot faster with PATH TRACING + LIGHT TRACING instead of Bidir Engine.
Just switch to path tracing and enable light tracing check box. Also don’t forget to increase Light tracing glossiness threshold a bit above your rough glass roughness setting.

1 Like

Here is a test with PATH TRACING + LIGHT TRACING instead of the Bidir Engine, I also enabled the adaptive sampling. This time the render went a lot faster (about 15 min), a downside is that most of the fine bounce light is now missing.


Nice ! you can get all that back with a good Photon Gi cache and caustic cache setting.
But first you have to rise your path deph to match Bidir.

If your Bidir bounce setting is :
eye path = 10
light path= 10
Then you need 20 for each path deph :

Diffuse 20
glossy 20
spec 20
total at least 20

Try to render with rised path deph and save the result before you enable caches

Then put all thoses settings in your caches :



Thanks again!

That pretty much solved everything :slight_smile:
Still some differences, if you look at the lamp shade for example, the image is also a bit brighter compared to just using bidir. But it doesn’t really make a noticeable difference, and in terms of speed this is far better!

ca 13 min render time:


Happy that it help you. Will be nice to update your first post with both Bidir and path + light tracing + light cache.
So others can learn from you.
About the difference between both. In fact the PT + LT + LC + CC is able to render details that can’t be seen by the holy Bidir. Yes current Bidir can’t render SDS path aka caustics seen in a mirror or inside a pool but viewed from outside.
Also LC can quickly catch small light detail compared to Bidir wich take hours to converge.


Was originally going to ask how the lighting was done but thankfully you’ve already said that! I’m going to try and use a similar effect when it becomes practical so thanks for the inspiration :smiley:

I featured you on BlenderNation, have a great weekend!

1 Like

Sorry, I forgot to add the link:

1 Like