SunMoon Object

Realsoft Graphics Oy		SunMoon Object
	Geometric Primitives

SunMoon object manages its first child object to simulate the position of the sun or the moon in a given date and a location.

The date is defined using local time. The applied time zone correction is geographical; the computation may include one hour error at certain time zones. The daylight saving time is not considered.

The location is defined by the usual longitude and latitude coordinates. Both coordinates should be given in decimal degree form (not as degrees.minutes.seconds).

Sun's position at Tampere, Finland 21 o'clock in the midsummer evening

To simulate the position of the sun or the moon, the sunmoon object rotates its first child object by its pivot point. This means that the azimuth and altitude angles of the selected target (sun / moon) can be found from the Rotate values of the object space of the first child. The first component, the heading angle, is the azimuth and the second component, the pitching angle, shows the altitude. Zero heading corresponds to the geographic north (= negative z axis of the sunmoon object space).

A sunmoon object can be created using the Sunmoon Tool. Some examples:

Point light sun

Create a point light, which represents the sun. You can add some visible objects like a glowing, shadow invisible sphere around the point light. Make sure all components of the sun are collected under a single hierarchy level. If not, select all components and apply Drop to level from the popup menu of the select window.

	Note
The position of the sun does not matter. However, its distance from the origin should be such that the visual size of the modeled sun appears correct when viewed from the origin. The distance should also be large enough (e.g 1000 times the size of the rest of the scene). Otherwise the position of the sun might change when the camera moves around the scene. However, do not try to use the real astronomical scale; the accuracy of computers is not sufficient for shadow computations from a light source that is millions of kilometers away from the illuminated objects.

Note

The position of the sun does not matter. However, its distance from the origin should be such that the visual size of the modeled sun appears correct when viewed from the origin. The distance should also be large enough (e.g 1000 times the size of the rest of the scene). Otherwise the position of the sun might change when the camera moves around the scene. However, do not try to use the real astronomical scale; the accuracy of computers is not sufficient for shadow computations from a light source that is millions of kilometers away from the illuminated objects.

Select the sun and click the SunMoon tool. It is located in the Light Sources tool tab.
Adjust the date and the location using the toolbar controls.

Distant light sun

Create a distant light, which represents the sun. The position of the light does not matter, but it should be carefully aimed towards the world origin. As with the point light, you can add some visible objects around the light. Collect all components of the sun under a single hierarchy level.
Select the modeled sun object and click the SunMoon tool.
Adjust the date and the location.


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