Steps to work with global illumination and photons

SET UP SCENE

Set up a building with an opening at the top this size:

feet or generic

SET UP LIGHTS

Give it 3 lights ...

MAKE SURE YOU TURN YOUR mr AREA SPOT LIGHT INTO mr AREA DIRECTIONAL

RENDER to determine general lighting

Render a very preliminary test:

GI = 5,000

Lights = 50,000

Some areas are very dark.

SET PHOTON SAMPLE RADIUS

Increase photons and set sample radius. You can make a little plane in the view to get a sense of how big you will want your photons.

I’m making mine 0.3 ...

INCREASE THE GLOBAL ENERGY MULTIPLIER

Open up the shadow areas! Experiment with increasing the energy multiplier number. 7 worked in this scene. The objective is, to get more photons into the black shadow areas.

Turn on final gather. Set FG radius to 10x the GI photon size.

Increase to 50,000 GI and 500,000 light ... shown here without FG: Also tweaked the Energy.

Now with the FG of 200:

Here we go increasing FG to 500 ... much longer than this to render is not much fun, and it looks pretty good. We could still work with energy, go back to light positions and multipliers, etc.

Sometimes you get a nasty blockiness.

Fix it this way, doubling the traced depth

It takes a lot of work to get photons that are not too erratic, in other words, not too bright and dark.

As you slowly increase the light photons, the paint blobs begin to blend together ...

As you increase the energy multiplier to open up the shadows, you also have to increase light photons.

It can be a difficult balance ... the goal is to get shadows that are not pitch black.

We have been using directional lights which are not supported. Switch to SPOT. We are also setting the light like this:

No FG! ... skylight is set very low, 0.2.

Turn on FG and use a skylight set to .6: