Frequently Asked Questions
I can not enable the BlendLuxCore addon, it shows errors
Most problems in this area stem from broken graphics driver installations. Try to re-install or update your graphics driver.
For Windows users:
- Make sure that you have installed the Visual C++ Redistributable Packages for Visual Studio 2013
- If you use v2.1alpha0 or later, you will also need:
If this does not solve the problem, browse the installation issues in the bug tracker to check if your error message was already reported. If it was not reported yet, open a new issue and copy the error message from the Blender console (on Windows, click Window -> Toggle System Console in Blender's menu. On Linux, start Blender from a terminal and try to enable the addon, then copy the error message from the terminal).
See the installation page for information on how to install, update and remove the BlendLuxCore addon.
Is there something like Cycles' Layer Weight/Fresnel/Facing node in LuxCore?
No, in LuxCore there is no direct equivalent to this node, because it would not work with the many algorithms in LuxCore that trace rays from lights (instead of from the camera), like the bidirectional engine, light tracing mode, or the PhotonGI cache.
Of course, all materials in LuxCore are physically based and have realistic fresnel effects built-in.
You can achieve a similar effect with the dot product node, but it will work only for one viewpoint:
Can Cycles materials be used in BlendLuxCore?
To an extent, yes. Many common Cycles shader nodes can be used in BlendLuxCore:
- You can enable this individually for each material with the "Use Cycles Nodes" option in the material properties.
- You can also enable it for the whole scene at once with the "Use Cycles Settings" button in the render properties. This will configure all materials, lights and the world to use Cycles settings
Not all Cycles nodes and settings are supported. Here is an overview: https://github.com/LuxCoreRender/BlendLuxCore/issues/272
Can 2D/3D mapping be driven by textures in LuxCore?
In general, no, because it would lead to much worse performance on GPUs.
However, if you only need to drive the translation part of a texture mapping, since LuxCore v2.5 you can use the distort texture for this purpose:
Texturing of rotation and scale is not yet possible.
What can be done against fireflies/hotpixels?
Sometimes, pixels appear that are much brighter than the surrounding pixels. Sometimes they are singular, sometimes clumped up. The underlying reason are light paths that are correct, but very hard to find with the current rendering algorithms, and thus they take much longer to render until noise-free than all other light paths in the image.
There are multiple ways to approach this problem:
- Try another rendering algorithm, it might be able to find the firefly-causing light paths much easier than the one you currently use. For example, try going to the render properties, open the Light Paths panel and enable "Light Tracing", or try the PhotonGI caustic cache, or try using the bidirectional engine.
- You can clamp the brightness of all light paths to a maximum value, in the render properties, Light Paths panel, "Clamping" setting. BlendLuxCore can auto-detect a value for this setting that is in the right ballpark for your scene if you render once without clamping enabled, but often this value will not be the best, so you will need a bit of trial-and-error to find a good value. Note that the clamping value depends on the lighting in your scene, so there is no one universally good clamping value, and you might need to adjust it if you add a new light source to your scene that is brighter than the others. Using a clamping value that is too low will result in a low-contrast, washed-out image, while a too high value will leave fireflies unaffected.
- Try to find out which lights or materials are responsible for the fireflies. There might be small, hard-to-find light sources that are causing them. Or a specular material is reflecting such a light source. If you are willing to alter the look of the scene, you can make such a light source more visible/larger, or lower the specularity of such a material. You can also make some light sources invisble to indirect light rays, thus eliminating fireflies (light properties, "Visibility" panel). This can be a good idea for the sun, for example, if your scene contains lots of specular materials.
Why is my HDRI environment black and not showing up?
You probably have other very bright light sources in the scene, for example a sun or a sky lamp.
Solution: raise the gain value of the area or HDRI light source that is black. The gain value might need to be very high, e.g. 100000.
Why is my area lamp black?
When I change the brightness of my lamp, nothing happens
You are probably using an automatic tonemapper which adjusts itself to the changed brightness, making it seem like the brightness did not change.
Solution: Use a non-automatic tonemapper (camera settings -> ImagePipeline).
When I make one of my lights brighter, all the other lights get darker (or vice versa)
Similar to #"When I change the brightness of my lamp, nothing happens".
You are using an automatic tonemapper which tries to keep the image at the same brightness, making it seem like the brightness of the lamps changed.
Solution: Use a non-automatic tonemapper (camera settings -> ImagePipeline).
A material/object appears to be flickering when I move the camera and shows artifacts in final render
This effect is called Z-fighting and is usually caused by mesh faces being exactly on top of each other, e.g. two planes on the same world coordinates.
- Check if there are two objects on top of each other, e.g. because you duplicated the object, cancelled the transform and forgot about it.
- Check if the mesh has duplicate faces. Enter edit mode and use the Remove Doubles button in the Tools panel, which might solve the problem in some cases.
Duplicate faces are often caused by extruding, cancelling the transform and forgetting about it.
There are dark triangular artifacts on my model, and I already checked for duplicate faces
Floating point numbers have a limited precision. When objects are very large (kilometers) or very small (micrometers), these precision issues become visible.
- If the object has a "normal" size (something like 1 cm to 1 km), but was scaled up/down by a huge amount, try to apply the scale (Ctrl+A -> Scale). For example, this often happens with imported CAD models.
- If applying the scale did not help and your object has to be very small or large, consider to bring it into the normal scale mentioned above, and pretend that it has a larger/smaller size. For example, if you make a model of the solar system, you will just have to make the earth something like 12.742 m in diameter, and pretend that 1 m of your model is equal to 10^6 m.
- If both options above are not usable in your case, you can raise the minimum epsilon that LuxCore uses. This setting can be found in the scene properties, Units panel, after clicking "Advanced LuxCore Settings". By default, the minimum epsilon is 0.00001. Try to raise it to 0.0001 (multiply by 10) for a start and see if the artifacts disappear. Do not set this value higher than necessary, because it will cause all sorts of hard-to-track problems. Be especially careful if you are rendering a scene with volumes.
An object that I set to "smooth shading" looks like it is shaded flat in shadow penumbras
This artifact is called "terminator problem".
Solution: Unfortunately there is no real solution. You can only try to mitigate the effect by subdividing the geometry further and/or increase the size of the light source that is causing the problem.
How do I setup liquid in a glass container correctly?
This forum thread shows an example: https://forums.luxcorerender.org/viewtopic.php?f=4&t=728#p7550