Labels:text | diagram | plan | technical drawing | parallel | black and white | schematic | line | font | screenshot OCR: VIRGE Integrated 3D Accelerator $3 Incorporated 3. Light - If a lit texture triangle is specified, the source pixel color is mixed with the texel color to generate a color which can optionally be fogged or alpha blended. 4. Fog - Also called depth cueing. As shown in Figure 15-7, the input can either be the source pixel color or the result of the filter/generate steps. 5. Alpha Blend - The source pixel color or the output of the fogging step (which may be disabled) is blended with the destination pixel color in video memory. This can produce a transparency effect. Each of these steps is explained in more detail in the following sections. 15.4.8.1 Texture Filtering Textures are stored in off-screen video memory at a location specified in MMB4EC. The integer components of the U and V parameters generate the memory addresses for each texture element, which is called a texel. The fractional part of the U and V parameters are used in the filter stage for interpolation between texel colors. The texture color format is specified in bits 7-5 of the Command Set register and can be one of the following: ODQ = 32 bits/pixel (ARGB9888) 001 = 16 blis/pixel (ARGB4444) 010 = 16 bits/pixel (ARGB1555) 011 = 8 bits/pixel (Alpha4, Blend4) 100 = 4 bits/pixel (Blend4, low nibble) 101 = 4 bits/pixel (Bland4, high nibble) 110 = 8 bits/pixel (palettizod) 111 = YU/YV (16 bits/pixel equivalent) DRAW DRAW LIT TRIANGLE LINE DRAW LIT 1MJANGLE DRAW USING BLEND4 UNLN TRIANGLE DRAW GOURAUD TRIANGLE FILTER EXTURE FILTER GENERATE LIGHT FOG ALPHA BLEND DRAW BUFFER Figure 15-7. Pixel Coloring ENHANCED PROGRAMMING 15-27
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