I begin by generating a terrain, opening a surface map, and choosing a sight line. When I am satisfied with the look of the scenery, I then go on to add rays to the scene. If you start with the sky, and get the rays first, you may find that they are strongest, or even only present at all, in the lower part of the sky, and adding scenery covers them up. You then have the choice of either doing away with the scenery and having nothing but sea, with perhaps some very low hills at the sides away from the rays, or using an improbably high viewpoint which often leads to sloping horizons and black gaps where sky and sea/land do not quite meet.
This shows the terrain I used for the tutorial scene, and the render with the default settings. I set the water level at -10m, because I wanted there to be a lake in the scene. I also wanted there to be some foreground visible. I would allow quite a tall mountain to the side, but needed the background mountains to be low so that there was a reasonable amount of sky in which to generate the rays. I chose a viewpoint which would give that sort of view. I used a surface map with grass on the gentle slopes and flat land, rock on the steep surfaces and snow on top of the mountains.
The first step in making the rays is to set certain essentials on the sun/light control panel. The three shadow options must all be checked. The sun must be a small disc with no corona. The position of the sun must be chosen in relation to the terrain you are using. You can place the sun anywhere in front of the camera, and the rays are usually more visible if the sun is high in the sky. In our picture, the presence of the tall mountain on the left makes the top right of the picture the obvious place for the sun, because in the centre it would unbalance the picture. We want the rays high up in the sky, so in fact the sun's centre needs to be above the picture itself. The lines either side of the sight line on the terrain generator show how much of the terrain will be included in the picture, and from this you can work out where on the edge of the terrain to put the sun to bring it to the right of the sky. Compare the sun heading diagram with the terrain and sight line above. The sun height I place originally so it is low enough to appear in the preview when I check it. From that I can adjust it right to left if I need to, and raise it and preview again until it is in the position I want.
A clear blue sky makes checking the sun position easier, so while I am placing the sun I take the density shift on the cloud generator down to -100, and I render sky only, not the land, to speed up the previews. The red 'X' in the image on the left shows the sun's location, slightly above the picture, but sufficiently close for its glow to be visible.
Once the sun is in position I take the density shift on the cloud control to 4. This is higher than the default level, but it seems to be an effective level for generating sunbeams. I preview the sky again, and the illustration on the right is the result with this sun position.
There are already visible rays, but they are only visible in the lower part of the sky, and once we put the scenery back they are covered up. But this is because the cloud almost completely covers the sky. So we know the sun position will produce rays, and what is needed are clouds of the right density and in the right position.
Looking at the scenery with the sun in position, there are other things that are going to need correcting. With the sun it that position, we are looking at the shadow side of the mountains and they are much too dark, especially the one in the left foreground. And there is a glaring patch of sunlight on the lake which is very distracting.
On the next page I will go through the settings used to transform this scene into a sunset scene with sunbeams around the clouds.