Lighting Dialog

With this dialog you can completely customize the lighting features in Terragen. This is a tabbed dialog box with settings for Direct Sunlight, Background Light, Sun's Appearance and Lighting of Atmosphere.

image of full lighting dialog

A note about lighting in Terragen

Terragen does its best to simulate real-world lighting conditions. Because of this, any changes you make to one setting may have an impact on the appearance of many aspects of the scene. For example, changing the sunlight colour and/or brightness will not only affect the lighting of the landscape, but also the sky. In particular, please note that "Background Lighting" settings have considerable effect on the appearance of the sky and clouds, not just the landscape.

direct sunlight - background lighting - sun's appearance - lighting of atmosphere

General lighting options

image of general lighting settings

These options are available whatever tab is selected.

Sun Heading/Altitude. Control where in the sky the sun appears. The lighting map gives a preview of what parts of the landscape are in light or shade.

Terrain Casts Shadows. Turns landscape shadow-casting on or off. There are very few reasons to turn this off, but switching it off will speed up landscape rendering.

Shadows in Atmosphere. Allows the landscape to cast shadows in the haze, allowing "sunbeams" in the haze. The effects of this are most apparent when the camera is looking towards the sun, because it permits the atmosphere to glow in front of the landscape. This adds greatly to the scene's realism and should almost never be disabled, but disabling it will speed up rendering, especially of the landscape. demonstration image
without atmospheric shadows
demonstration image
with atmospheric shadows

Direct Sunlight tab

image of direct sunlight tab

Specify Sunlight Colour / Realistic Sunlight Penetration System. Two different methods of lighting the scene. Many of the options are not available with the "Specify Sunlight Colour" system. The Realistic method also takes into account the altitude of the sun and the atmospheric conditions, to simulate realistic sunlight colour and brightness as it passes through the atmosphere (most apparent when rendering sunset scenes). demonstration image
specify sunlight colour
demonstration image
realistic penetration system

Effect of Atmosphere. Adjusts how much the atmosphere actually affects the sunlight. This adds more "thickness" to sunsets etc. The default of 100% is fine for most scenes, and altering the atmospheric conditions allows you to achieve the right sunlight effect.

Percent Cloudcover. This determines the shadow amount below the cloud layer when Cloud shadow-casting is not in use. Cloud shadow-casting is never used in current versions of Terragen, so this setting controls how deep into shadow the landscape and haze is below the cloud layer.

Background Lighting tab

image of background lighting tab Single Colour Lighting modeanother view of the background lighting tab Multi-directional Lighting mode

Single Colour / Multi-directional Lighting. The Single Colour mode allows you to specify a colour for the illumination of the shadows and allows simple control over the appearance of the shadows. The Multi-directional mode uses the three colours (Diffuse Sunlight, Light from Above, and Reverse Light) to illuminate the shadows from multiple directions. If used well, the multi-directional option can improve the realism of scenes where most or all of the landscape is in shadow.

Shadow Lightness. This allows an overall control over how bright or dark the shadows are by scaling the brightness of the shadow colour (single colour mode) or shadow lights (multi-directional mode).

When rendering sunset scenes, more realism can often be obtained by reducing the Shadow Lightness and increasing Exposure (on the Rendering Control). The most important thing is to experiment to see what looks best.

These following options are only available in Multi-directional Lighting Mode.

Sun's Appearance tab

suns' appearance tab

Disc Diameter. Controls how large the sun appears in the sky. This also affects the softness of the shadows - a smaller diameter leads to harsher shadows. The default of 1 degree is a suitable value for earthbound scenes (although for scientific accuracy, a more realistic value would be 0.5).

Corona Size. This does not simulate what astronomers call the sun's corona. It is a halo around the sun which partly compensates for the fact that Terragen does not yet render lens flare. It has the effect of softening the edge of the sun's disc.

Lighting of Atmosphere tab

lighting of atmosphere tab

Glow Amount. Controls how much the sun causes the haze to glare near the sun. This is the most useful of the two settings.

Glow Power. Adjusts the falloff power for the glow. Most of the time, the default of 100% is fine. Changing this is useful when creating very cloudy or hazy scenes, where low settings for Glow Power are much more realistic. Glow Power works well if you think of it as the "transparency" of the atmosphere near the sun. High values may make the centre of the glow very bright but regions of the haze which are away from the sun may appear very dark.

Atmosphere. Shows the Atmosphere dialog.



render controls

landscape

water

clouds

atmosphere

lighting

image
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©May, 1999 John McLusky