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/*
* Created by Brian Kelleher; Oct 1985
*
* Include file for filled polygon routines.
*
* These are the data structures needed to scan convert regions. Two
* different scan conversion methods are available: the even-odd method,
* and the winding number method. The even-odd rule states that a point is
* inside the polygon if a ray drawn from that point in any direction will
* pass through an odd number of path segments. By the winding number
* rule, a point is decided to be inside the polygon if a ray drawn from
* that point in any direction will pass through a different number of
* clockwise and counter-clockwise path segments.
*
* These data structures are adapted somewhat from the algorithm in
* (Foley/Van Dam) for scan converting polygons. The basic algorithm is to
* start at the top (smallest y) of the polygon, stepping down to the
* bottom of the polygon by incrementing the y coordinate. We keep a list
* of edges which the current scanline crosses, sorted by x. This list is
* called the Active Edge Table (AET). As we increment the y-coordinate,
* we update each entry in the AET to reflect the edges' new xcoords. This
* list must be sorted at each scanline in case two edges intersect. We
* also keep a data structure known as the Edge Table (ET), which keeps
* track of all edges that the current scanline has not yet reached. The
* ET is basically a list of ScanLineList structures containing a list of
* edges which are entered at a given scanline. There is one ScanLineList
* per scanline at which an edge is entered. When we enter a new edge, we
* move it from the ET to the AET.
*
* From the AET, we can implement the even-odd rule as in (Foley/Van Dam).
* The winding number rule is a little trickier. We also keep the
* EdgeTableEntries in the AET linked by the nextWETE (winding
* EdgeTableEntry) link. This allows the edges to be linked just as before
* for updating purposes, but only uses the edges linked by the nextWETE
* link as edges representing spans of the polygon to drawn (as with the
* even-odd rule).
*/
typedef struct _EdgeTableEntry {
int ymax; /* ycoord at which we exit this edge. */
BRESINFO bres; /* Bresenham info to run the edge */
struct _EdgeTableEntry *next; /* next in the list */
struct _EdgeTableEntry *back; /* for insertion sort */
struct _EdgeTableEntry *nextWETE; /* for winding num rule */
bool ClockWise; /* flag for winding number rule */
} EdgeTableEntry;
typedef struct _ScanLineList{
int scanline; /* the scanline represented */
EdgeTableEntry *edgelist; /* header node */
struct _ScanLineList *next; /* next in the list */
} ScanLineList;
typedef struct {
int ymax; /* ymax for the polygon */
int ymin; /* ymin for the polygon */
ScanLineList scanlines; /* header node */
} EdgeTable;
/*
* Here is a struct to help with storage allocation
* so we can allocate a big chunk at a time, and then take
* pieces from this heap when we need to.
*/
#define SLLSPERBLOCK 25
typedef struct _ScanLineListBlock {
ScanLineList SLLs[SLLSPERBLOCK];
struct _ScanLineListBlock *next;
} ScanLineListBlock;
/*
* number of points to buffer before sending them off
* to scanlines() : Must be an even number
*/
#define NUMPTSTOBUFFER 200
/*
*
* A few macros for the inner loops of the fill code where
* performance considerations don't allow a procedure call.
*
* Evaluate the given edge at the given scanline.
* If the edge has expired, then we leave it and fix up
* the active edge table; otherwise, we increment the
* x value to be ready for the next scanline.
* The winding number rule is in effect, so we must notify
* the caller when the edge has been removed so he
* can reorder the Winding Active Edge Table.
*/
#define EVALUATEEDGEWINDING(pAET, pPrevAET, y, fixWAET) { \
if (pAET->ymax == y) { /* leaving this edge */ \
pPrevAET->next = pAET->next; \
pAET = pPrevAET->next; \
fixWAET = true; \
if (pAET) \
pAET->back = pPrevAET; \
} \
else { \
BRESINCRPGONSTRUCT(pAET->bres); \
pPrevAET = pAET; \
pAET = pAET->next; \
} \
}
/*
* Evaluate the given edge at the given scanline.
* If the edge has expired, then we leave it and fix up
* the active edge table; otherwise, we increment the
* x value to be ready for the next scanline.
* The even-odd rule is in effect.
*/
#define EVALUATEEDGEEVENODD(pAET, pPrevAET, y) { \
if (pAET->ymax == y) { /* leaving this edge */ \
pPrevAET->next = pAET->next; \
pAET = pPrevAET->next; \
if (pAET) \
pAET->back = pPrevAET; \
} \
else { \
BRESINCRPGONSTRUCT(pAET->bres); \
pPrevAET = pAET; \
pAET = pAET->next; \
} \
}
extern bool miInsertionSort ____P((EdgeTableEntry *AET));
extern void miCreateETandAET ____P((int count, const miPoint *pts, EdgeTable *ET, EdgeTableEntry *AET, EdgeTableEntry *pETEs, ScanLineListBlock *pSLLBlock));
extern void miloadAET ____P((EdgeTableEntry *AET, EdgeTableEntry *ETEs));
extern void micomputeWAET ____P((EdgeTableEntry *AET));
extern void miFreeStorage ____P((ScanLineListBlock *pSLLBlock));
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