The scene now is filled with a number of photons, carrying a lot of energy. Their color assumes the color of the last surface they hit. The size of these photons is based on the scene size (normally about 10% of the scene with Maxium Sampling Radius unchecked)..
In the Light Properties group: Increase the Average GI Photons per Light to: 20,000 Hit render (F9)
Increase the Average GI Photons per Light to: 50,000 Hit render (F9)
The photons start to blend.
Increase the Average GI Photons per Light to: 100,000 Hit render (F9)
Go up to Global Illumination group and check Maxium Sampling Radius to 20. This helps blending those photons. Hit render (F9)
As you can see, the GI effect starts to be more visible. However, it leaves the artefacts because of the photon granularity. The photons alone cannot be enough, so, we will have to use Final Gather to fine-tune the image, and take the effect of the Skylight. Mental ray's Final Gather works the same way with Regather in radiosity. It samples the scene rendered pixel, or averages between sparse samples.
In Final Gather group:
- Check Enable
- Set Samples to: 300 (1000 by default, but we need only 300 for testing purpose)
Hit render (F9)
Global Illumination effect is now clearly visible, contributed by the Skylight. But, now, we have a problem. First, somewhere in the scene look a bit dark, as should not be. Second, the artefacts have not really been fixed; and shift to the shadow.