Comparing GI Settings Cinema 4D / BodyPaint 3D Program Documentation Tutorials Light and Shadow Tutorial Visualizing Interior Spaces using Global Illumination
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Comparing GI Settings

Let’s compare individual GI Methods and their advantages and disadvantages using a rendered image as an example. So far we have only used a combination of IC and LM but there are several other possible combinations as well. The render times listed below are not binding but can vary depending on the settings, resolution and hardware.

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QMC + QMC: 2h13m

First we will test a QMC image. This is a very time-consuming method but provides the highest level of quality. No GI artefacts are visible and only a slight grain can be seen, which is due to the low Sample Count of 32. The Diffuse Depth remains set to 2 to shorten render time. The result is slightly darker and, as expected, the render times are quite long.

QMC + Irradiance Cache: 2h3m

QMC can also be combined with a different Secondary Method such as Irradiance Cache. This method helps us get rid of the graininess typical for QMC but the render times remain very long.

QMC + Radiosity Maps: 25m25s

One way of reducing render times for GI scenes is to use Radiosity Maps. This method uses limited Sample Counts, which makes it better suited for outdoor scenes or product visualizations. The scene will be made darker but the render times are much faster than the previously named methods.

QMC + Light Maps: 28m20s

If you replace Radiosity Maps with Light Maps, the render times will be much faster and the Maximum Depth can be increased greatly (in this example to 16). Such a high Maximum Depth value produces a much more realistic-looking lighting. This is the prefect way to get low render times with QMC quality.

Irradiance Cache + QMC: 1h35m

In our case it’s not a good idea to use QMC as a Secondary Method with IR as a Primary Method. Render times for an interpolated solution are quite high and a lot of GI artefacts would be produced.

Irradiance Cache + Irradiance Cache: 13m50s

If we use Irradiance Cache for both methods we will get our render result much faster and it will look much cleaner with regard to GI artefacts. The Diffuse Depth is set to 8, which is he maximum for this combination.

Irradiance Cache + Radiosity Maps: 8m42s

As already mentioned, Radiosity Maps are good for speeding up rendering but not suited for interior scenes. Even though the render times are the fastest, the scene appears dark due to the limited number of samples. Note, for example, how unnaturally dark the region around the window looks.

Irradiance Cache + Light Maps: 7m44s

Finally, the method that was used for the tutorial, IR and LM. The render times are the lowest, we can define up to 128 light reflections (here the default value of 16) and the settings can also be quickly modified. We get the best compromise between quality and fast render times.

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