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All three methods function at the pixel level, and therefore shadowing and mirroring

inside the 3D scene (as permitted by ray tracing methods) are not possible..

With the the Shadow button you can provide a 3D object with a shadow. By

changing the Surface angle you can influence the form of the shadow (see Figure

153). The left sphere has a surface angle of 0° (the paper represents a perpendicular

surface behind the object) while the right sphere has a surface angle of 45°. With 90°

the paper would be directly under the object.

Figure 153: Shadows using

different surface angles

The shape and size of the the shadow are also influenced by the lighting properties.

These can be adjusted on the Illumination page of the dialog. Multiple light sources

for shadows are not yet supported. The shadow properties can be set for individual

objects in a drawing but where objects form part of a 3D scene, the shadow produced

is that of the entire scene.

It is possible to set the shadow property for single objects using the Area property.

The shadow is then shown with the color selected in the shadow dialog, but again the

representation of the lighting of the scene determines the end result of the entire

scene. In this way, colored shadows, with different distances to the object, and

different color and transparency effects can be created.

In the Camera field of the shading dialog the settings of the virtual camera can be

changed. These settings relate only to the view in central projection and apply to the

entire 3D scene. The Distance parameter is used to adjust the spacing between the

camera and scene. The default value for an extruded body is equal to the depth or

length of the body. With equal length edges front and rear, the effect at large

distances is quite small. The standard value of Focal length is 10cm. It has the same

significance as with a real camera. Larger focal lengths simulate a telephoto lens,

smaller ones a wide-angle lens. The effect that changes in the camera settings have

on an object are shown in Figure 154.

Figure 154: Effect of camera settings

Chapter 7 Working with 3D Objects 125

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OpenOffice.org OpenOffice - 3.3 Guía de usuario Pagina 125