2. Creating Sunbeams

We will start with pretty much default settings. In this example world, atmosphere settings are the default, as are the Lightning Conditions settings. The terrain I used was 1025x1025, and the metres point spacing was the default 30m. (Note: this setting does affect sunbeam visibility.)

Step 1 I created clouds with quite small size setting (2nd smallest), hoping to get many sharp sunbeams. But larger clouds may give nice beams, too. Increase cloud density contrast and density shift so that most of the sky is covered with clouds. Increasing Darkening value makes sunbeams more visible against the darker background. In addition, I adjusted the gamma value sligthly lower, to 1.7 (from the default 2.0). Cloud  Largest cloud size:  2/9 Density contrast:   70 Density shift: 30 Darkening: 45% Gamma: 1.7 Sunrays are not visible, since we have not yet enabled Clouds Cast Shadows option.
Step 2 Turn on the Clouds Cast Shadows option on Lightning Conditions window. This should make clouds shadows and sunrays visible.  √   Clouds Cast Shadows But what now? Everything went dark. The whole landscape is covered by cloud shadow. This is because the Atmosphere Accuracy setting is too low.
Step 3 Increase Atmosphere Accuracy setting (Render Settings button on Rendering Control window). In this case increasing the setting just one step from the default middle position would already create sunbeams, but I increased two steps (to the maximum) to get sharper beams. Accuracy: Atmosphere   3/5 -> 5/5 Note: Cloud Shading Accuracy setting does not affect sunbeams, and there is rarely need to increase the setting from the default middle position. Alternatively, you could decrease the metres point spacing setting (click Size button on Landscape window). Reducing the value from 30m to 15m would make sunbeams visible even if you keep the Atmosphere Accuracy setting in the default middle position.
Step 4 You can make the sunbeams more visible by increasing Simple Haze Density setting in Atmosphere window. I also increased Atmoshperic Blue setting slightly to compensate for color change caused by the haze. Simple Haze: Density   20% -> 40% Atmoshperic Blue: Density   20% -> 25% You could further enhance the beams by increasing Sunlight Strength setting or decreasing Shadow Lightness, but these affect the light and shadows on the ground, too. Note, however, that it is not good idea to overdo the effect. Too strong beams would look quite unnatural.

On the next page, the effect of Atmosphere Accuracy setting on different Cloud Sizes is studied.