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Managing 3D Objects and Bitmaps
The Shading mode refers to the method that Draw uses to render objects and their
interaction with light. Draw offers three choices: Flat, Phong and Gouraud.
Flat is the quickest technique, but it also gives the worst results (all of the faces are
visible).
Phong is an intermediate technique.
Gouraud renders objects with the highest quality.
In the above drawing, flat shading (left) is clearly less attractive, whereas it is more difficult
to distinguish between Phong (middle) and Gouraud shading (right). One might simply note
that the shading appears to be more realistic with Gouraud shading than with Phong shading.
The shadow area of the dialog lets you display shadows under 3D objects. By changing the
surface angle, you can obtain shadows that look more elongated or less elongated:
The first 3D sphere has a shadow with a surface angle of 0° (the paper is vertical) and the
second has a surface angle of 45° (paper inclined at 45°).
You can also see that the shadow is displayed in such a way that it corresponds to the angle
of illumination of the sphere.
The other parameters on this page let you define the focal length and distance of the virtual
camera that displays the 3D object. The closer the camera (focal distance), the greater the
effect of perspective. In Figure 33, the same box is shown on the right, but with a shorter
focal distance for the one on the left:
These two settings belong to the selected object(s). In general, it is better for these settings to
be the same for all 3D objects in the drawing.
Draw Guide 66
Figure 31 - Shading examples. From left to right: Flat,
Phong, Gouraud.
Figure 32 - 3D shadowing using a surface angle of 0° (left)
and 45° (right).
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