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** New User Tips and Tricks **
If you don't know where to start, then head over to the Flatpak-LuxRender Code page.
Next, grab Flatpak-LuxBlend25 from its respective GitHub page.
It must be reiterated that LuxRender tries to simulate how light behaves in the real world. So, do yourself a favor and check your scale. As an example, 1 Blender unit = 1 meter, so your glass of water is actually 5 meters tall.
The default and recommended render settings (unless you use GPU rendering which limits choices) are MLT (Metropolis Light Transport) + Bidir (Bidirectional Path Tracing). For general renders you should almost always use this combination. Metropolis is an intelligent and unbiased sampler.
Again Metropolis + Bidirectional is going to give the best results.
Generally Metropolis + Path but again Metropolis + Bidirectional will work very well here, so try both.
Metropolis sampler with a low "large mutation probability" and a high "max consecutive rejections" + Bidirectional.
Higher path depth (Bidirectional or Path) is better. However, you start getting diminishing returns over 50-64. In other words, rendering starts to slow down with too many bounces.
For animations a more predictable outcome is preferable to the sometimes unpredictable render times of the Metropolis sampler. In this case, the Low Discrepancy sampler is preferable. Generally, the Bidirectional integrator will give the best if you want complete, accurate global illumination. You may find that the Distributed Path or Path integrators with a low maximum depth setting give faster results.
Either use:
- Metropolis + Direct Lighting or
- Low discrepancy Hilbert + ExPhotonMap with a low pixel samples setting (1-4), fewer photons, and optionally no final gather.
To ask Luxrender to automatically focus on noisy areas, enable the "noise-aware" option in the sampler settings.
A setting has been added for firefly rejection. This setting is available in LuxBlend25, but you can add it manually to the scene file. This setting goes in the "Film" area of the .lxs file and shouldn't need to go over 10 (consult the included Scene File Format reference for details). Even a setting of 1 wil usually produce great results. There is a small speed hit, but if your scene is prone to generating fireflies, this is worthwhile.
If you are using the Metropolis sampler, you can also decrease the "maxconsecrejects" option. It will remove fireflies but will also create a more biased result.
If you use GPU rendering, be aware some materials have not been implemented yet.
The most important thing to remember about material settings is to never use extreme RGB values over 0.8 or below 0.2 (0.9 and 0.1 are pushing the edge of the envelope). If your values are too high it will cause fireflies, and such values are just not realistic. Values that are too low are not realistic either, but are not as much of a problem. A piece of white office paper is roughly equivalent to 0.8 - 0.9 depending on who you ask. But even if you use 0.8 for paper you can adjust the tone mapping settings so it looks nice and white. For matte translucent the reflection and transmission parameters in each RGB column should not add up to more than 1. If you have a reflection value of 0.6 0.6 0.6, then your transmission value can not be higher than 0.4 0.4 0.4.
If you have glass in your scene and it looks black inside, first check your normals, then try increasing the maximum depth of your integrator (when using Bidirectional or Path). If you still have black areas, you may have overlapping meshes or incorrect geometry.
Bump maps are relative. When creating a bump map, if you use 50% grey it will be neutral and have no effect on the bump. White is raised, and black is sunken by the chosen amount. If you start with a black background, you can never go "into" the mesh with the bump.
The default Blender cube is 2 meters by 2 meters or 6 feet by 6 feet. When learning to model in Blender, many users do not pay attention to that. But when you realize that your glass of water is 5 meters tall (15 feet) you begin to rethink how you model. One solution is to model your object, then scale it down and apply the scale. So instead of 5 meters you might scale to 5 inches or 0.127 Blender units tall. Google calculator is good for those who don't normally think in metric. Then apply the scale to the model.
If you end up with weird dark areas in your render, please check to make sure all of your normals are facing out in to the world. The "Backface Culling" option in the Blender viewport can assist you in identifying incorrect normal orientation.
Shown in black is the plain triangle used for intersection; in blue are the shading normals and the corresponding surface orientation. Shown in green is the smooth surface approximated by the triangle and its shading normals, and the ray is shown in red.
As you can see, the ray is above the triangle and below the surface defined by the shading normal. This is inconsistent and prevents LuxRender from computing a sensible reflection or refraction. This is because the ray's position ends up below the surface of the smoothed normal.
The only way to eliminate this artifact is to increase the number of faces in the object, such as by applying a subdivision modifier.
The same issue can happen with other glossy or reflective objects.
Low poly count can make the edges black if they are marked as smooth shaded. The fix is to either make the edges sharp (by setting the mesh to "Flat Shading" in Blender) or to subdivide the model.
Black edges due to "Smooth Shading" on a low-poly object.
Black edges fixed after subdivision.