Luxrender Help!

Hi Guys!

I’ve dipped into Luxrender here and there over the years, but I still don’t seems to be getting scenes to look correct or render in a reasonable time. I think somewhere in my workflow I’m doing something wrong. Here’s a simple archviz interior I’ve been working on for testing purposes between render engines.

  1. A room with wall, floor and ceiling thickness modelled to real world scale.
  2. For the light source I add a sun lamp to point towards the window.
    2a) the Sun is set at it’s defaults, Gain 1.000, Importance 1.00. Sun & Sky with Shadow ray samples: 1 and turbidity: 2.00. This seems a little low, but I’m not 100% certain.
  3. Add a plane to the outside window and set it as a “PORTAL” with the Normals pointing in towards the room.
  4. I setup the material for the glass and set it to “Architectural”
  5. I use the suggested render option “MLT” unbiased.
  6. Used the option under camera “Firefly Rejection” option and set to 4 (suggested by Blender Cookie.
  7. Hit render, then watch as Lux opens and develops the image.
  8. While Lux is rendering, I change the “Linear” exposures to get the image to what I consider to be appropriate and balanced for the exposure.
  9. Then let cook, which seems to take ages, way too long to work efficiently. The noise doesn’t clear up very quickly – a simple room as described above with no textures and just Matte for materials is so slow incredibly so :frowning:
    My Efficiency is 1700%+ This I thought was good, but if I was to do a fully modelled/textured scene, I’d approximate 2-3 days rendering, is this normal?

I have a Win7 64Bit Core I3, with 7GB. - 4xThreads

Is this the correct method for such as scene, or am I missing something really obvious? Do I have to worry about the volumes, especially with the window glass?

Secondly I’ve just downloaded the latest release:
LuxRender 0.8 x64 OpenCL Setup.exe (

I was hoping to make use of the GPU option for OpenCL MLT+Bidirectional as I could do with a little speed enhancement, but as soon as I hit render it finishes and doesn’t attempt to load Luxrender External.
In the Blender Console I get these errors:

WARNING: Colour Management is switched off, render results may look too dark
INFO: Creating LuxRender context
Incompatible Lightstrategy for Hybrid Bidir (use “one”)
ERROR: Export aborted: Incompatible render settings

What’s going on?

My Nvidia card has the latest drivers and it’s a GeForce GTX 560 Ti (1GB) – I have no problem with cycles GPU using Cuda.

While I’m asking for help, might as well get it off my chest :wink:

I have Pylux installed, but I notice that the Blenders render window image differs from the lux render window, different colours and contrast etc. I’m not particularity bothered about it, but I was wondering why it was different?

Thanks for any help on this, I’ve always wanted to put Luxrender into one of my projects, but I never get very far. I’ve also watched numerous tutorials, but none of them seem to follow the exact same method and frequently miss this that others have suggested.

Jay :wink:

check new LuxRender 1.0 alpha

color management
you can set it with Internal


For still image i would use Reinhard 2005 tonemapping (i think Lux use old 2002)
Paper about Reinhard 2005:

Yafaray Thread:

I just started playing around with Lux again. I pulled down the 1.0 release that is OpenCL enabled. But the GPU stuff still does not work. Quite disappointing after experiencing it working with Cycles. There is also some python sub library you have to install manually, which seems like a bad development path to take. Why can’t they just include it in the ZIP or install?

I guess I just have to ask? Has anyone experienced GPU acceleration using Lux? What is the trick to making it work?

The only way I have managed to get quick renders out of Lux is to use Direct Lighting. All other modes are too slow for my impatient self.

If you are passing through glass, you may want to turn up that shadow ray sample to 3 or more.

It seems like with Lux I spend more time conducting test, thinking I am doing something wrong, rather than producing results.

I have encountered lots of little small errors in LuxBlend itself which makes me wonder if some of these errors are just parameters not get relayed to Lux correctly?

On some platforms at least, it IS included in the zip. There’s no reason not to include it. I know it is on OS X. Is it not on some other platforms? I can let the packagers know they should be including it

There are two GPU modes at the moment, one of them is a simple path tracer, and the other (hybrid bidir) is unfinished, it’s included as an experimental feature, at least for now (it has no MIS at the moment).

Shadow ray samples does not affect glass, the only thing that setting helps with getting rid of penumbra noise on shadows. Path depth is the one that helps with glass

Like what?