ELSA GLoria-L, Руководство пользователя

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All About Graphics
ELSA GLoria-L, -L/MX, -XL, -XXL
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Scaling on the screen ––The above steps are now calculated for three-dimen-
sional space using normalized coordinates. The on-screen image coordinates will
only now be computed.
Rendering
At this stage, the 3D scene is filled with color shades and textures are applied. Different
processes and methods are also applied here.
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Texture mapping ––At this stage, the 3D object undergoes a sort of "face lift". The
materials and textures are assigned. Different methods are used here to make the
textures appear realistic, even when enlarged or reduced. As a first step, the tex-
tures are computed:
– Point sampling is the simplest method. A pixel-by-pixel comparison is made
between the texture template and the surface to be filled. This method leads to
a very coarse representation, especially when enlarged.
– In linear mapping, a new color value is interpolated from the adjacent pixels (or
telexes) of a texture. This gives better results than point sampling, as the hard
boundary between the coarse pixels is blurred.
– The MIP mapping method stores a large number of enlargement stages for the
texture. The depth information of a primitive is then used to determine which
enlargement stages of the texture will be used in drawing. Normal textures sel-
dom contain more than 256 colors.
The first 15 bits of a 16-bit wide color representation are reserved for the colors
(5/5/5 > R/G/B). Information concerning the transparency of the texture is car-
ried in the alpha channel. The last bit is reserved for this information. Finally, a
distinction is made in MIP mapping between bilinear and trilinear filtering. Bilin-
ear filtering interpolates between two pixels of two textures, trilinear filtering
interpolates between four pixels for each of two textures.
– Bump mapping introduces a new dimension. Relief or raised textures can only
be generated with the other methods in two dimensions using light and shadow
effects. In bump mapping, the texture is additionally assigned height informa-
tion, which allows very realistic three-dimensional effects to be created.
The staircase effect is corrected by anti-aliasing. This is either done by interpolating
mixed pixels, in which a new color value is computed from two adjacent color val-
ues, or by using transparent pixels of the same color which are overlaid over adja-
cent pixels.
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Shading ––Shading takes account of the effects created by different light sources
on the 3D object and provide for a very realistic overall impression. Here, too, there
are different methods which are more or less processor-intensive:
– Flat shading assigns a color value to each polygon. This results in a mosaic-like,
jagged representation, which demands only a short processing time.