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4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * Created by Brian Kelleher; Oct 1985
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * Include file for filled polygon routines.
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * These are the data structures needed to scan
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * convert regions. Two different scan conversion
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * methods are available -- the even-odd method, and
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * the winding number method.
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * The even-odd rule states that a point is inside
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * the polygon if a ray drawn from that point in any
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * direction will pass through an odd number of
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * path segments.
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * By the winding number rule, a point is decided
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * to be inside the polygon if a ray drawn from that
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * point in any direction passes through a different
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * number of clockwise and counter-clockwise path
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * segments.
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * These data structures are adapted somewhat from
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * the algorithm in (Foley/Van Dam) for scan converting
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * polygons.
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * The basic algorithm is to start at the top (smallest y)
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * of the polygon, stepping down to the bottom of
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * the polygon by incrementing the y coordinate. We
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * keep a list of edges which the current scanline crosses,
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * sorted by x. This list is called the Active Edge Table (AET)
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * As we change the y-coordinate, we update each entry in
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * in the active edge table to reflect the edges new xcoord.
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * This list must be sorted at each scanline in case
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * two edges intersect.
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * We also keep a data structure known as the Edge Table (ET),
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * which keeps track of all the edges which the current
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * scanline has not yet reached. The ET is basically a
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * list of ScanLineList structures containing a list of
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * edges which are entered at a given scanline. There is one
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * ScanLineList per scanline at which an edge is entered.
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * When we enter a new edge, we move it from the ET to the AET.
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * From the AET, we can implement the even-odd rule as in
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * The winding number rule is a little trickier. We also
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * keep the EdgeTableEntries in the AET linked by the
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * nextWETE (winding EdgeTableEntry) link. This allows
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * the edges to be linked just as before for updating
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * purposes, but only uses the edges linked by the nextWETE
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * link as edges representing spans of the polygon to
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * drawn (as with the even-odd rule).
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * for the winding number rule
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync BRESINFO bres; /* Bresenham info to run the edge */
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync struct _EdgeTableEntry *next; /* next in the list */
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync struct _EdgeTableEntry *back; /* for insertion sort */
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync struct _EdgeTableEntry *nextWETE; /* for winding num rule */
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsynctypedef struct {
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * Here is a struct to help with storage allocation
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * so we can allocate a big chunk at a time, and then take
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * pieces from this heap when we need to.
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * number of points to buffer before sending them off
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * to scanlines() : Must be an even number
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * a few macros for the inner loops of the fill code where
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * performance considerations don't allow a procedure call.
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * Evaluate the given edge at the given scanline.
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * If the edge has expired, then we leave it and fix up
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * the active edge table; otherwise, we increment the
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * x value to be ready for the next scanline.
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * The winding number rule is in effect, so we must notify
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * the caller when the edge has been removed so he
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * can reorder the Winding Active Edge Table.
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync#define EVALUATEEDGEWINDING(pAET, pPrevAET, y, fixWAET) { \
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * Evaluate the given edge at the given scanline.
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * If the edge has expired, then we leave it and fix up
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * the active edge table; otherwise, we increment the
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * x value to be ready for the next scanline.
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * The even-odd rule is in effect.
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync int /*scanline*/,
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync int * /*iSLLBlock*/
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync int /*count*/,