LuxCoreRender Forums

Hi. I have been preparing a scene in Cycles and after a bit of thought I decided to finally make an attempt with Luxcore.

This is what I have so far from cycles:

The problem that I find with cycles is setting the acrylic surface correctly. As you can see the only way that I found to get the light pass through the surface and cast the grid shadow on the floor was to use a light pass plugged in the shadow rays. The drawback: I lose the shadow of the acrylic on the floor.

Anyways ...I have heard so many good things about luxcore speed and quality I decided to give a try.

This is my first attempt with luxcore ...I did not tweak anything in the scene. Added a sky + sun. The acrylic ...its not looking good, but its probably cause I just copy the glass material from the sample scenes in your web.

I want to keep trying with luxcore...I did not have much time to research, I will do it tomorrow after work. I do have some questions:

Sky+Sun
I am looking for an accurate representation for the natural light. I am using the sky for the environment light (driven by a sun lamp). Almost all the parameters need to be left as they are in order to achieve a realistic sun light. Is that correct? I am using "use sun gain" in the sky and driving everything by the sun. I activated in the sun "Normalize by color" . I also noticed by hovering on the "gain" parameter It will say needs to be 1 if you are using a tonemaper.
My camera has 3 options for tonemapper. Which one do you usually pick for having an accurate sunlight ?

Acrylic
I am not super convinced by the look. I believe it looks like solid glass even if the material I picked is glass and changed the IOR to acrylic (1.492) It also looks that is darkening the light that goes through it and the shadows cast on the floor do not have the grid detail. As I said I did not experiment so much , might be I need to increase bounces ? Also the acrylic have the typical dark edges...those ones I got rid by using the light pass node in cycles.

Speed
This is the most scary part...luxcore has a lot of parameters. I know I am doing something wrong cause Its way too slow. The render I posted is 500 samples and I did not check the time...but it was way slower than cycles. I am using the parameters as they come in luxcore 2.5 I also have white spots...but to be honest I am planning to wath the Dravia tutorial on the parameters in youtube...


All this things I am asking are just cause I am a bit anxious and maybe someone replies during the night.

I will keep trying till I get the render I want in Luxcore.
Thank you a lot

Actually, the Cycles rendering is totally faked, you can obtain the same result in Lux but I assume it is not what you are looking for.

This is due to the limitation of a plain path tracer like Cycles (or Lux in the default configuration).

First of all you need to enabled hybrid rendering to be able to efficiently render caustics and see a grid of light on the floor (by using path tracing + light tracing). They are SD paths: Specular(=glass) + Diffuse(=floor material) aka caustics.

Second you need to render SDS path too (Specular+Diffuse+Specular) to render the light going trough the glass, hitting the wood, going trough the glass again and hitting the eye. SDS are very difficult to render and only few render can render that kind of light paths. Lux can if you enable the caustic cache.

Short version: it is a lot simpler if you can post the scene and we can set up the rendering for you.

Short version: it is a lot simpler if you can post the scene and we can set up the rendering for you.

I agree !

Thank you so much! I am at work I will try to find a brake and send it to you! Is there anyway to send it privately? Maybe I can post the scene with the acrylic and a few wood parts? Its a project I would like to build and I prefer to not have it floating freely

I really appreciate your help!

zooropa wrote: ↑Thu Sep 10, 2020 9:25 am Maybe I can post the scene with the acrylic and a few wood parts?

Yes, just sun+floor+bare bone glass+bare bone wood will work.

Thanks! How can I send it to you privately? Just a direct message? Also I do not know if Dravia wants it too...I could also sent to you. Not sure how to call users by writing "@"

zooropa wrote: ↑Thu Sep 10, 2020 12:12 pm How can I send it to you privately? Just a direct message?

Yes, you can use a forum private message.

Sent a private message I am not sure if the other user wants it Dravia. How do you poke a community user in this forum? In blender artist works with @ not sure here.

I have been watching more Dravia videos and also reading what you described. Now the light trace is active and looks way more realistic that all the hacks I needed to do in cycles. I also learn with the tutorials that the glass an advance section in the output where I needed to change the shadows to white....and now I can see the plastic as it should be! Its getting closer....

I noticed in the video tutorials from Dravia that sometimes he adds an homogeneous node to the volume in the glass materials...As I understand I do not need to do that with acrylic.

I do notice the plastic still looks like a solid thick glass...in the refractions, specially in the corners...I am wondering if that is cause I built it mainly using modifiers. I will give a try by building it from scratch without modifiers, only with the subdivision one...I am thinking if the solidify is messing something...

It feels the acrylic closer to a magnifying glass than a crystal clear plastic. Dont you think so ?

Here my latest tryout .

An actual real world image of what you want to achieve can help (preferably in same condition ....bright sun).