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2-2. Polygon in SGL

SGL supports only polygons with 4 vertices. For this reason, polygons with 3 or 5 vertices cannot be represented. However, by setting two vertices of the four vertices to the same coordinate, a polygon with three vertices can be drawn.
Edges are always connected clockwise, regardless of vertex number.

Figure 2-2 Example of polygons in Sega Saturn

Sega Saturn draws polygons as filled areas on the screen. The procedure for drawing a polygon is as follows.

1. Vertex coordinate list creation
2. Polygon surface list creation
3. Determines the surface attribute for each polygon surface
4. Draw on screen

Next, referring to the actual drawing routine, we will explain the related functions and function parameters.

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