Render optimization tips

This page lists a few tips on things to avoid in your scene setups and materials to keep render times low and avoid excessive noise.


Geometry: Make sure your emitting surfaces are as low-polygons as possible. Usually a single sided polygon will suffice. 

Not enclosed: If possible, do not completely enclose your emitters inside a dielectric object. All light that is emitted through the dielectric object is considered caustic light and will take longer to render.

Not intersecting: Make sure your emitter is not intersecting other geometry. In most cases this will not be a problem but it may add to the render time and produce strange results in the lighting. Regular geometry can intersect other geometry.

Strength: Keep your emitters at real world values. If your render is turning out too dark, don´t raise the power to several thousands of watts as that will break the realism and can also introduce more noise in the render. Instead, you should control the exposure by using the camera exposure settings (f-Stop, Shutter speed, ISO).


Number of ML sliders: the more separate emitter sliders you have, the more RAM Maxwell needs as each light channel must be stored separately while rendering. If you do not necessarily need separate emitter control for all emitters you can "merge" them by applying the same emitter material to the geometries.

Color ML: This option will require more RAM than Intensity-only ML, because each RGB channel must be stored separately while rendering. Avoid this mode if you don't need to also change the color of the emitters while rendering.

Saturated/bright materials (very important)

Do not use 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 is better to decrease the saturation a bit. For a white wall, around RGB 220, 220, 220, which is the albedo of white paper, is sufficient. See the page Realistic material reflectance for more info.

AGS (Architectural Glass Solution)

For interior renders where window glass reflections are necessary, use the AGS glass material for the windows instead of real glass. This will create the reflections but will not produce caustics, thus speeding up the rendering. You can find more about AGS glass materials on the Material examples - How To (AGS) section. 


Deciding between the two displacement methods available in Maxwell Render (on-the-fly and pretesselated), you should take into consideration the following:

  • both methods will render faster if the underlying base mesh is already somewhat subdivided - this means that you can lower the precision parameter and still have detailed displacements. Otherwise, if you are trying to have a detailed displacement on a single polygon plane for example, Maxwell has to internally subdivide the mesh many times, either while rendering with the on-the-fly method, or before rendering, with the pretesselated method. With the first method this will mean an increase in render time, with the second method this will mean an increase in the RAM usage.

  • for small height displacements with lots of fine detail, the on-the-fly method can be very fast, and is recommended since it will not consume any extra RAM, no matter how high the precision parameter is.

  • if your render computer has a lot of RAM you can use the pretesselated displacement which renders much faster in most cases compared with the on-the-fly displacement.

  • the adaptive option for the on-the-fly displacement should not be used for the final render, it can instead be used as an initial "test" of the displacement texture, to see how much displacement detail can be extracted from a particular texture. But for very large displacement textures, if you have the adaptive option on, Maxwell will try and subdivide the geometry down to the very last pixel of the texture, which will increase render time a lot. In most cases you don´t need such detailed displacements and you can instead control the detail with the precision parameter to balance detail vs render time.


Render Channels