PAGE 9C

THE SUN'S RAYS

Making changes

It is possible to generate very different scenes using these settings with only minor changes.

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In this scene, the terrain has been replaced by a flat one with only water, to illustrate the effects of the sunbeams when they are not obscured by mountains and can reflect in the sea.

To remove the terrain, I used the Modify Terrain button on the terrain generator, and then clicked on Clear/Flatten. The water level was set at 1m., because the default flat terrain has a nominal height of 0m., and the water level has to be above that height for water to be visible.

The sunbeams and the associated shadows are reflected in the water, and the cloud is casting a shadow across the water. You could use this effect in a scene with a long expanse of sea at the horizon, with mountains confined to low ones at the outside edges on the horizon, and/or some coming down one or both sides of the scene, if you wanted some land in the picture.

The banding in the cloud is a known rendering problem with Terragen 0.8.11, which may be addressed in later versions.

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To render this scene as a daylight one instead of a sunset, I changed settings on the atmosphere controller and on the sun/light controller.

On the atmosphere controller the simple haze and decay sliders were taken to 20% and the simple haze colour set to 123 on each colour slider.

The sunlight strength was reduced to 500% and the glow amount and glow power set at 100%.

The rays could have been made to look more pronounced by reducing the exposure setting in the camera settings on the render controller to its default level. There is a reset button which will do this. But it lowered the lighting level over the whole picture and made it look a bit too dark for a daylight scene. I then tried raising the simple haze to 70 and the sunlight strength to 1000 - combination which does sometimes improve the look of sunbeams, but in this case it washed them out altogether. These settings serve to show that although sunbeams look more pronounced in a sunset scene, they can also be visible in a midday one. However, changing the clouds can bring a dramatic improvement.

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You can see how much stronger these rays are, with different clouds. In fact, I was able to make them better than they first appeared by raising simple haze to 70 and sunlight strength to 1000 - the settings used for this rendering. The clouds seem to be the key to good sunbeams, and it is worth perservering until you get some which work well. I generated and previewed clouds for over half an hour before getting these. They also serve to show that settings which wash out the rays with one set of clouds will improve them with another. This is not an exact science!

The downside of increasing simple haze is that contrast is lost in the scene. If the improvement in the sunbeams is worth that, you can often improve the overall look of the scene by increasing the contrast in an art package - but you cannot do that if you are entering a scene in a contest where no post-processing is permitted. Then you must balance the simple haze level, sunlight strength, and overall look of the picture to get the best effect.

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Finally, I want to look at another scene, and I will give a list of the settings used for this one, because they are rather different from the ones used in the first one, and will give you an idea of the variety of combinations of parameters which you can try to generate sunbeams. Settings which work well in one scene may produce nothing in another.

This scene has a much higher viewpoint than the first one, which gives a larger expanse of sky for the rays. But this brings problems. If you look carefully in the white dotted circle, you can see that there is a black gap where sky and sea do not quite meet. Normally you would deal with this by adjusting the sky size on the cloud generator, but this was such a small area, even in the full size render, that I decided to remove it by cloning in Paint Shop Pro, rather than risk losing the sunbeams by changing the cloud settings. It would be much worse if there were no mountains obscuring the horizon over most of its length, and as well as covering the gap, they serve to hide the fact that with a high viewpoint the horizon slopes.

The surface map was the same grass, rock and snowcapped mountains one used in the first scene. These are the settings used for this scene. Default settings are those in place when you first load Terragen.

Water control
Water level -10m. Roughness and wave size 40. Visibility effect 100. Direct sunlight 50%. Reflection spread 6. Nothing else changed from default settings.

Cloud control
Altitude 150. Depth/thickness 10. 3d clouds unchecked. Density contrast 50. Density shift 7. Darkening 62%. Clouds generated at the default size. Nothing else changed from default settings.

Atmosphere
Simple haze density 31%. Light decay/red density 70%. Nothing else, including colours, changed from default settings.

Lighting conditions controller
All three shadows boxes checked. Sun heading and altitude 180 and 28.339 to place the sun towards the left of the sky, and high enough to be just out of the picture above the scene. These two parameters are, of course, peculiar to this terrain and sight line and would have no relevance in a different scene.
Direct Sunlight tab: Sunlight strength 500%. Effect of atmosphere 100%. Percent cloud cover 8%. Realistic sunlight penetration system checked.
Background light tab: Shadow lightness 100%. Multi-directional shadow lighting checked.
Sun's appearance tab: Disc diameter 1. Corona size 0.
Lighting of atmosphere tab: Glow amount 100%. Glow power 80%.

Render control
Nothing changed from default settings except preview slider fully over to the right.

These settings have produced a scene which is lighter than the previous one, and gives an impression of morning rather than sunset light. You can see the full size render of the scene here.

This brings to an end our study of atmospheres. We shall turn next to the more advanced features of the terrain generator.

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