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Spherical: The enclosing sphere is calculated for the object and then

projected onto the object. This form of calculation produces an object with a

smoother surface; the edges of individual segments are more smoothly

rounded than with the Object-specific effect (see Figure 150). However

surfaces that meet at a point do not show a realistic lighting effect.

Invert Normals: This results in a reversal of the lighting direction. The inside

of the body then becomes the outside. This property is particular to each

individual object.

Double sided illumination: The lighting is also computed for the inside of the

object. In other cases the lighting value for the outside is simply transferred

to the inner side. This property is of interest for open objects. It is a property

of the 3D scene and affects all objects in the scene.

Figure 150: Cylinder with 10 segments

a= Object-specific b=Flat, c=Spherical

The following table shows the linkage between double-sided illumination and inverted

normals.

The light source is on the

right.

Normals

not inverted

Normals inverted

No double sided illumination

With double sided

illumination

3D Effects - Shading

The Shading page offers functions for shading the object surface, adding shadows

and choosing camera settings.

Shading is a rendering method involving a consideration of lighting ratios, which is

used to produce curved 3D surfaces. The surfaces are broken down into small

triangular segments. Draw offers three methods to produce this effect: Flat, Phong

and Gouraud. The setting selected applies to all objects in the 3D scene.

Chapter 7 Working with 3D Objects 123

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