mipoly.h (6486B)
1 /* 2 3 Copyright 1987, 1998 The Open Group 4 5 Permission to use, copy, modify, distribute, and sell this software and its 6 documentation for any purpose is hereby granted without fee, provided that 7 the above copyright notice appear in all copies and that both that 8 copyright notice and this permission notice appear in supporting 9 documentation. 10 11 The above copyright notice and this permission notice shall be included 12 in all copies or substantial portions of the Software. 13 14 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS 15 OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 16 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. 17 IN NO EVENT SHALL THE OPEN GROUP BE LIABLE FOR ANY CLAIM, DAMAGES OR 18 OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 19 ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR 20 OTHER DEALINGS IN THE SOFTWARE. 21 22 Except as contained in this notice, the name of The Open Group shall 23 not be used in advertising or otherwise to promote the sale, use or 24 other dealings in this Software without prior written authorization 25 from The Open Group. 26 27 */ 28 29 /* 30 * fill.h 31 * 32 * Created by Brian Kelleher; Oct 1985 33 * 34 * Include file for filled polygon routines. 35 * 36 * These are the data structures needed to scan 37 * convert regions. Two different scan conversion 38 * methods are available -- the even-odd method, and 39 * the winding number method. 40 * The even-odd rule states that a point is inside 41 * the polygon if a ray drawn from that point in any 42 * direction will pass through an odd number of 43 * path segments. 44 * By the winding number rule, a point is decided 45 * to be inside the polygon if a ray drawn from that 46 * point in any direction passes through a different 47 * number of clockwise and counter-clockwise path 48 * segments. 49 * 50 * These data structures are adapted somewhat from 51 * the algorithm in (Foley/Van Dam) for scan converting 52 * polygons. 53 * The basic algorithm is to start at the top (smallest y) 54 * of the polygon, stepping down to the bottom of 55 * the polygon by incrementing the y coordinate. We 56 * keep a list of edges which the current scanline crosses, 57 * sorted by x. This list is called the Active Edge Table (AET) 58 * As we change the y-coordinate, we update each entry in 59 * in the active edge table to reflect the edges new xcoord. 60 * This list must be sorted at each scanline in case 61 * two edges intersect. 62 * We also keep a data structure known as the Edge Table (ET), 63 * which keeps track of all the edges which the current 64 * scanline has not yet reached. The ET is basically a 65 * list of ScanLineList structures containing a list of 66 * edges which are entered at a given scanline. There is one 67 * ScanLineList per scanline at which an edge is entered. 68 * When we enter a new edge, we move it from the ET to the AET. 69 * 70 * From the AET, we can implement the even-odd rule as in 71 * (Foley/Van Dam). 72 * The winding number rule is a little trickier. We also 73 * keep the EdgeTableEntries in the AET linked by the 74 * nextWETE (winding EdgeTableEntry) link. This allows 75 * the edges to be linked just as before for updating 76 * purposes, but only uses the edges linked by the nextWETE 77 * link as edges representing spans of the polygon to 78 * drawn (as with the even-odd rule). 79 */ 80 81 /* 82 * for the winding number rule 83 */ 84 #define CLOCKWISE 1 85 #define COUNTERCLOCKWISE -1 86 87 typedef struct _EdgeTableEntry { 88 int ymax; /* ycoord at which we exit this edge. */ 89 BRESINFO bres; /* Bresenham info to run the edge */ 90 struct _EdgeTableEntry *next; /* next in the list */ 91 struct _EdgeTableEntry *back; /* for insertion sort */ 92 struct _EdgeTableEntry *nextWETE; /* for winding num rule */ 93 int ClockWise; /* flag for winding number rule */ 94 } EdgeTableEntry; 95 96 typedef struct _ScanLineList { 97 int scanline; /* the scanline represented */ 98 EdgeTableEntry *edgelist; /* header node */ 99 struct _ScanLineList *next; /* next in the list */ 100 } ScanLineList; 101 102 typedef struct { 103 int ymax; /* ymax for the polygon */ 104 int ymin; /* ymin for the polygon */ 105 ScanLineList scanlines; /* header node */ 106 } EdgeTable; 107 108 /* 109 * Here is a struct to help with storage allocation 110 * so we can allocate a big chunk at a time, and then take 111 * pieces from this heap when we need to. 112 */ 113 #define SLLSPERBLOCK 25 114 115 typedef struct _ScanLineListBlock { 116 ScanLineList SLLs[SLLSPERBLOCK]; 117 struct _ScanLineListBlock *next; 118 } ScanLineListBlock; 119 120 /* 121 * number of points to buffer before sending them off 122 * to scanlines() : Must be an even number 123 */ 124 #define NUMPTSTOBUFFER 200 125 126 /* 127 * 128 * a few macros for the inner loops of the fill code where 129 * performance considerations don't allow a procedure call. 130 * 131 * Evaluate the given edge at the given scanline. 132 * If the edge has expired, then we leave it and fix up 133 * the active edge table; otherwise, we increment the 134 * x value to be ready for the next scanline. 135 * The winding number rule is in effect, so we must notify 136 * the caller when the edge has been removed so he 137 * can reorder the Winding Active Edge Table. 138 */ 139 #define EVALUATEEDGEWINDING(pAET, pPrevAET, y, fixWAET) { \ 140 if (pAET->ymax == y) { /* leaving this edge */ \ 141 pPrevAET->next = pAET->next; \ 142 pAET = pPrevAET->next; \ 143 fixWAET = 1; \ 144 if (pAET) \ 145 pAET->back = pPrevAET; \ 146 } \ 147 else { \ 148 BRESINCRPGONSTRUCT(pAET->bres); \ 149 pPrevAET = pAET; \ 150 pAET = pAET->next; \ 151 } \ 152 } 153 154 /* 155 * Evaluate the given edge at the given scanline. 156 * If the edge has expired, then we leave it and fix up 157 * the active edge table; otherwise, we increment the 158 * x value to be ready for the next scanline. 159 * The even-odd rule is in effect. 160 */ 161 #define EVALUATEEDGEEVENODD(pAET, pPrevAET, y) { \ 162 if (pAET->ymax == y) { /* leaving this edge */ \ 163 pPrevAET->next = pAET->next; \ 164 pAET = pPrevAET->next; \ 165 if (pAET) \ 166 pAET->back = pPrevAET; \ 167 } \ 168 else { \ 169 BRESINCRPGONSTRUCT(pAET->bres); \ 170 pPrevAET = pAET; \ 171 pAET = pAET->next; \ 172 } \ 173 }