OpenOffice.org OpenOffice - 3.3 Guía de usuario descargar pdf (Pagina 124)

• Flat is the fastest and simplest method. For every individual segment a special

color tone is determined, based on the lighting ratio and the direction of the segment

area. This tone is used for the whole area of the segment. The segmentation is clearly

visible.

• Phong is the most time-consuming method. With this method, for each pixel the

associated normal is determined by interpolation, based on the normals of the

segment edges. This causes the segment area to appear curved and the segment

intersections are no longer visible.

Figure 151: Shading page

• Gouraud is a relatively quick method. It determines the color value for the

segment corners and calculates the color value for every pixel through linear

interpolation. The segment edges are still recognizable, but significantly less so than

with the flat method. The Gouraud method considers only light reflection on diffuse,

reflecting surfaces (dispersal).

Figure 152: Flat, Phong and Gouraud shading

In Figure 152 the left sphere was rendered with flat shading, the middle with Phong

and the right with Gouraud. The quality of the flat method is clearly inferior to the

other two. The difference between Phong and Gouraud is small. With the Gouraud

method the segments can be very faintly seen and rendered objects have a slightly

less “shine” than with the Phong method.

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OpenOffice.org OpenOffice - 3.3 Guía de usuario Pagina 124