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Rendering FAQ

Rendering FAQ

Owned by Systems Next Limit (Unlicensed)
Last updated: 15 Apr, 2020 by Next Limit

1. My render comes out black, even though I've added emitter materials.

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Maxwell Emitters behave according to real-world parameters. Therefore, it is necessary to:

  • First of all, check the scale of your scene (which you can do by importing your MXS file into Maxwell Studio). As Maxwell Render is a light simulator, scene scale is very important - you cannot illuminate a 2 km2 area with a 60 Watt light bulb.
  • Check the normals of your emitter objects. You can try reversing them with the "Reverse" normals button in the Object Parameters panel, and then rendering again.
  • Check your camera settings, particularly the f-Stop, Shutter speed and ISO parameters. If there is not enough light coming into the camera, the image will be black.
  • Make sure that the Emitter power is defined correctly. (Don't forget efficacy for watt-based emitters.

2. My image is extremely noisy even after a long render time. What should I do

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There are several things you can do to optimize a scene, mostly related to emitters:

  • Make sure your emitting surfaces are as low-poly as possible. Usually, a single-sided polygon will be sufficient.
  • If possible, do not completely enclose your emitters inside a dielectric object.
  • Make sure your emitter is not intersecting other geometry.
  • Very important: do not include very white or fully saturated materials in your scene. For example, a completely white (255, 255, 255) material will take a very long time to clear and will also make the contrast in the image disappear. Also avoid completely saturated colors such as pure red (255, 0, 0). Pure white or pure saturated materials do not exist in real life so it's better to decrease the saturation a bit. For a white wall, around RGB 220 or less is sufficient.
  • For interior renders where window glass reflections are necessary, use the Architectural Glass Solution (AGS) for the windows instead of real glass. This will create the reflections but will not produce any caustics, thus speeding up the rendering. - Perhaps you simply need more time for rendering, depending on your machine specs. 

3. Some polygons render black. What should I do? 

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- Make sure your geometry does not have any coplanar polygons that share the same space.
- After importing your geometry into Maxwell Studio you might want to select the object and press "Recalc normals" in the Object Parameters panel to remove any possible normal errors.
- Check that your object doesn't have any reversed normals by checking the "show normals" checkbox in the Object Parameters panel. Fix any reversed normals by clicking on the Reverse Normals button in the Object Parameters panel. 

 4. I have black horizontal bands in my render.  

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Materials with components in Additive mode could generate those bands under certain lighting conditions (the Additive mode doesn't clamp the total energy to 100% like the Normal mode does, but adds it, and under some lighting conditions it could exceed the physically correct limit of a material reflecting more energy that what it receives, producing numeric artifacts). This is an indication that the materials are reflecting too much energy back into the scene.

Although we can not avoid users mixing their layers in Additive mode (with the risk of exceeding the energy limits), we strongly recommend not to use more than 2 Layers at 100% weight set to Additive mode.

5. How can I render my scenes on another computer?

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You can use the Pack & Go feature found in most of the plugins and also from Maxwell Studio. In Studio, open your MXS file (Maxwell scene file). Go to File>Pack & Go and choose an output folder. Studio will copy the MXS file and any other files needed to render the scene (textures, IOR, IES, HDR files etc) to the folder. You can then just copy this folder to another computer and render. The paths to the textures specified in the MXS file will still point to paths relevant to the old computer, but because with Pack & Go the textures are copied to the same folder where the MXS file is, Maxwell will also look in this folder when searching for textures so the render will start normally.

6. Can I compare the Benchmarking values or Sampling Level values between Maxwell Render 1 and Maxwell Render 2 to compare the performance of the new version?

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No. The Sampling Level and Benchmark values are performance ratios that depend on the calculation algorithms. For Maxwell Render 2.x we redesigned the rendering algorithms inside the engine, so the new Sampling Level or Benchmarking values are only useful for comparing Maxwell Render 2 scenes. Given that the same SL value gives you a much higher quality and cleaner render in Maxwell Render 2.x than in Maxwell Render 1.x, it makes no technical sense to compare the values from two different engines.
The only useful parameters for comparison between Maxwell Render 1.x vs. Maxwell Render 2.x are time and image noise.

7. Does rendering in Low priority mean my renders will be slower?

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No necessarily. The Low render priority simply means that if you want to work at your computer at the same time that Maxwell is rendering, the render process will have a lower priority to the CPU so that you can work comfortably in other tasks while Maxwell is rendering. But if you don't use your computer (or work with low CPU intensive tasks) Maxwell will still use the full capacity of your CPUs.

8. Does Maxwell Render work with gimp xcf files?

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No. For a full list of supported image formats, please see Rendering in Maxwell.

9. I get a different framing on the final rendered image than what I had on my 3D platform viewport 

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This is related to the camera sensor aspect ratio, that surely differs from the render aspect ratio.

As a real camera, Maxwell needs both aspect ratios to be equal. Check the section about Camera Sensor size and Render resolution in this page for a further explanation.

10. What is a recommended standard resolution for print (i.e. for an A2 print)? 

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That's a very deep topic that depends on many factors. The most important factors are the required viewing distance and the printing device specifications (dots per inch). Of course the final resolution must fulfill your printing device specifications, that obviously vary from billboard to magazine print.
But keep in mind that rendering larger does not always equate to display more details, since you bake the maximum amount of detail already into the scene when you modeled and textured it. Unlike reality, where you will see increasingly more detail the closer you get, a 3D scene will in fact get worse and worse after a certain point. In case you have no other indication, you can remind that the majority of renderings used in billboards archviz projects are around 4k to 6k pixels. Higher than that, an hypothetic 15k render would not show more detail (due the modeling and texturing limitation mentioned above) while the rendering process and memory needed would even not be affordable.

There are of course some situations, mainly on visualization of hard surface objects like technical pieces or jewelry, that could eventually benefit from rendering larger than 4k-6k since they consists on an accurate rendition of edges and corners, and other media that demand more resolution than billboards.




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