Soft Lighting ON. The shadows at points B and C are diffused and not sharp as they are in the image below. If you follow the shadow at point A towards the tiled wall, you can see that it becomes more diffuse and lighter the further away you get from the object that is casting the shadow. Likewise, if you look at the highlight on the bottle at point D, it is less sharp than the rendering below

Soft Lighting OFF. The shadows here are as if generated by a true point source (which they are). In the "real world", this would never happen. Even if you were to use a fabulously bright and tiny light source, there would still be some light spillage due to surrounding objects, atmosphere and the fact that the light has a physical size.. even if small. You might get shadows like this in outer space or from very bright sunlight, but here on earth it doesn't often happen.

 

How is Soft Lighting achieved?

As I mentioned above, it's a bit of a cheat, but its also an emulation of what happens in the real world. You simply create a cluster of radial lights. You can use other types of light but in my experience, radial seems to be the most effective, but hey, have a play and prove me wrong!

 

Types of Light.

I have split the types of light I use into 2 categories:

Ordered Softlight. This consists of 1 bright central light with other dimmer lights in orbit.
Random Softlight Just a random collection of dim lights. The easiest way to create this is to File/Multi-replicate, and then Randomise with 3D disperse/rotate. There are about 20 lights used here.

As you can see, there is significant "banding" on the floor shadow in both cases. This can be minimised by changing the brightness of the lights, the size of the cluster and most importantly, using a suitable material on the floor. I have heard mention of "spiral" light clusters being used by others but have not tried these myself.

Changing the Brightness:

Firstly, ensure that the lights are set to Squared falloff in the Edit lights box. This is not strictly necessary, but since I generally find I use these clusters for artificial lighting, it seems to work best. Additionally, with the large numbers of lights in the scene, you will soon find that you are in a situation where the light is just too bright. Squared Falloff will help to tone things down a bit. In order to adjust any of the lighting properties, you will have to ungroup the cluster. If you edit them immediately after ungrouping and whilst they are all selected , they can be easily re-grouped once changed. This will not work for the Ordered Softlight since the central light has to be brighter than the satellite lights, if you make all the satellite lights one group it may make things easier. I mentioned earlier a problem with over-saturation due to the number of lights in the scene. If you find this is a problem and you have already turned your light values down to "1" and can go no lower, then try selecting varying shades of grey or other dark colours for your lights.

Size of the Cluster:

Try to make the size of the overall cluster approximate the size of the light source which you envisage illuminating the scene. In the examples shown above, the cluster is about the size of the sphere and about 2 spheres distance away. The smaller you make the cluster, the narrower the bands. The distance from the object will also have an effect. The further away, the narrow the bands. Try experimenting with the size and distance to achieve satisfactory results. If you are going to do a scene in close up, you may need to increase the number of lights in the cluster.

Materials:

The easiest way to minimise the banding effect is to use bumpy or heavily textured materials for the object that is receiving the shadows. A bit obvious really, but then the most effective things normally are!

Rendering Times:

The major down side to using soft light clusters is the corresponding increase in rendering time. It seems that if you have 20 lights in a scene, then it will take approximately 20 times the amount of time to render. If you have volumetric rendering turned on or many reflective/refractive surfaces in your scene then why not go for a weekend break while you wait ....The glass study used at the top of the page took a tad over 26 hours to render using soft lighting and 2 hours using a single light source.

Well, that's it. I hope this has proved useful and given you a few pointers. If you come up with any new ideas of your own, drop me a line and let me know.

 

Tony.

If you would like to see the first result of my radiosity solution, click here.