Main Page | Namespace List | Class Hierarchy | Class List | File List | Namespace Members | Class Members | Related Pages

poly-generic.h

00001 /* $TOG: poly.h /main/5 1998/02/06 17:47:27 kaleb $ */ 00002 /************************************************************************ 00003 00004 Copyright 1987, 1998 The Open Group 00005 00006 All Rights Reserved. 00007 00008 The above copyright notice and this permission notice shall be included in 00009 all copies or substantial portions of the Software. 00010 00011 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 00012 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 00013 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 00014 OPEN GROUP BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN 00015 AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN 00016 CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. 00017 00018 Except as contained in this notice, the name of The Open Group shall not be 00019 used in advertising or otherwise to promote the sale, use or other dealings 00020 in this Software without prior written authorization from The Open Group. 00021 00022 00023 Copyright 1987 by Digital Equipment Corporation, Maynard, Massachusetts. 00024 00025 All Rights Reserved 00026 00027 Permission to use, copy, modify, and distribute this software and its 00028 documentation for any purpose and without fee is hereby granted, 00029 provided that the above copyright notice appear in all copies and that 00030 both that copyright notice and this permission notice appear in 00031 supporting documentation, and that the name of Digital not be 00032 used in advertising or publicity pertaining to distribution of the 00033 software without specific, written prior permission. 00034 00035 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING 00036 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL 00037 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR 00038 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, 00039 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, 00040 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS 00041 SOFTWARE. 00042 00043 ************************************************************************/ 00044 00045 /* 00046 * This file contains a few macros to help track 00047 * the edge of a filled object. The object is assumed 00048 * to be filled in scanline order, and thus the 00049 * algorithm used is an extension of Bresenham's line 00050 * drawing algorithm which assumes that y is always the 00051 * major axis. 00052 * Since these pieces of code are the same for any filled shape, 00053 * it is more convenient to gather the library in one 00054 * place, but since these pieces of code are also in 00055 * the inner loops of output primitives, procedure call 00056 * overhead is out of the question. 00057 * See the author for a derivation if needed. 00058 */ 00059 00060 00061 /* 00062 * In scan converting polygons, we want to choose those pixels 00063 * which are inside the polygon. Thus, we add .5 to the starting 00064 * x coordinate for both left and right edges. Now we choose the 00065 * first pixel which is inside the pgon for the left edge and the 00066 * first pixel which is outside the pgon for the right edge. 00067 * Draw the left pixel, but not the right. 00068 * 00069 * How to add .5 to the starting x coordinate: 00070 * If the edge is moving to the right, then subtract dy from the 00071 * error term from the general form of the algorithm. 00072 * If the edge is moving to the left, then add dy to the error term. 00073 * 00074 * The reason for the difference between edges moving to the left 00075 * and edges moving to the right is simple: If an edge is moving 00076 * to the right, then we want the algorithm to flip immediately. 00077 * If it is moving to the left, then we don't want it to flip until 00078 * we traverse an entire pixel. 00079 */ 00080 00081 // Stolen from Gtk+ and C++-ized by Ron Steinke, January 2003 00082 00083 #define BRESINITPGON(dy, x1, x2, xStart, d, m, m1, incr1, incr2) { \ 00084 int dx; /* local storage */ \ 00085 \ 00086 /* \ 00087 * if the edge is horizontal, then it is ignored \ 00088 * and assumed not to be processed. Otherwise, do this stuff. \ 00089 */ \ 00090 if ((dy) != 0) { \ 00091 xStart = (x1); \ 00092 dx = (x2) - xStart; \ 00093 if (dx < 0) { \ 00094 m = dx / (dy); \ 00095 m1 = m - 1; \ 00096 incr1 = -2 * dx + 2 * (dy) * m1; \ 00097 incr2 = -2 * dx + 2 * (dy) * m; \ 00098 d = 2 * m * (dy) - 2 * dx - 2 * (dy); \ 00099 } else { \ 00100 m = dx / (dy); \ 00101 m1 = m + 1; \ 00102 incr1 = 2 * dx - 2 * (dy) * m1; \ 00103 incr2 = 2 * dx - 2 * (dy) * m; \ 00104 d = -2 * m * (dy) + 2 * dx; \ 00105 } \ 00106 } \ 00107 } 00108 00109 #define BRESINCRPGON(d, minval, m, m1, incr1, incr2) { \ 00110 if (m1 > 0) { \ 00111 if (d > 0) { \ 00112 minval += m1; \ 00113 d += incr1; \ 00114 } \ 00115 else { \ 00116 minval += m; \ 00117 d += incr2; \ 00118 } \ 00119 } else {\ 00120 if (d >= 0) { \ 00121 minval += m1; \ 00122 d += incr1; \ 00123 } \ 00124 else { \ 00125 minval += m; \ 00126 d += incr2; \ 00127 } \ 00128 } \ 00129 } 00130 00131 00132 /* 00133 * This structure contains all of the information needed 00134 * to run the bresenham algorithm. 00135 * The variables may be hardcoded into the declarations 00136 * instead of using this structure to make use of 00137 * register declarations. 00138 */ 00139 typedef struct { 00140 int minor_axis; /* minor axis */ 00141 int d; /* decision variable */ 00142 int m, m1; /* slope and slope+1 */ 00143 int incr1, incr2; /* error increments */ 00144 } BRESINFO; 00145 00146 00147 #define BRESINITPGONSTRUCT(dmaj, min1, min2, bres) \ 00148 BRESINITPGON(dmaj, min1, min2, bres.minor_axis, bres.d, \ 00149 bres.m, bres.m1, bres.incr1, bres.incr2) 00150 00151 #define BRESINCRPGONSTRUCT(bres) \ 00152 BRESINCRPGON(bres.d, bres.minor_axis, bres.m, bres.m1, bres.incr1, bres.incr2) 00153 00154 00155 00156 /* 00157 * These are the data structures needed to scan 00158 * convert regions. Two different scan conversion 00159 * methods are available -- the even-odd method, and 00160 * the winding number method. 00161 * The even-odd rule states that a point is inside 00162 * the polygon if a ray drawn from that point in any 00163 * direction will pass through an odd number of 00164 * path segments. 00165 * By the winding number rule, a point is decided 00166 * to be inside the polygon if a ray drawn from that 00167 * point in any direction passes through a different 00168 * number of clockwise and counter-clockwise path 00169 * segments. 00170 * 00171 * These data structures are adapted somewhat from 00172 * the algorithm in (Foley/Van Dam) for scan converting 00173 * polygons. 00174 * The basic algorithm is to start at the top (smallest y) 00175 * of the polygon, stepping down to the bottom of 00176 * the polygon by incrementing the y coordinate. We 00177 * keep a list of edges which the current scanline crosses, 00178 * sorted by x. This list is called the Active Edge Table (AET) 00179 * As we change the y-coordinate, we update each entry in 00180 * in the active edge table to reflect the edges new xcoord. 00181 * This list must be sorted at each scanline in case 00182 * two edges intersect. 00183 * We also keep a data structure known as the Edge Table (ET), 00184 * which keeps track of all the edges which the current 00185 * scanline has not yet reached. The ET is basically a 00186 * list of ScanLineList structures containing a list of 00187 * edges which are entered at a given scanline. There is one 00188 * ScanLineList per scanline at which an edge is entered. 00189 * When we enter a new edge, we move it from the ET to the AET. 00190 * 00191 * From the AET, we can implement the even-odd rule as in 00192 * (Foley/Van Dam). 00193 * The winding number rule is a little trickier. We also 00194 * keep the EdgeTableEntries in the AET linked by the 00195 * nextWETE (winding EdgeTableEntry) link. This allows 00196 * the edges to be linked just as before for updating 00197 * purposes, but only uses the edges linked by the nextWETE 00198 * link as edges representing spans of the polygon to 00199 * drawn (as with the even-odd rule). 00200 */ 00201 00202 /* 00203 * for the winding number rule 00204 */ 00205 #define CLOCKWISE 1 00206 #define COUNTERCLOCKWISE -1 00207 00208 typedef struct _EdgeTableEntry { 00209 int ymax; /* ycoord at which we exit this edge. */ 00210 BRESINFO bres; /* Bresenham info to run the edge */ 00211 struct _EdgeTableEntry *next; /* next in the list */ 00212 struct _EdgeTableEntry *back; /* for insertion sort */ 00213 struct _EdgeTableEntry *nextWETE; /* for winding num rule */ 00214 int ClockWise; /* flag for winding number rule */ 00215 } EdgeTableEntry; 00216 00217 00218 typedef struct _ScanLineList{ 00219 int scanline; /* the scanline represented */ 00220 EdgeTableEntry *edgelist; /* header node */ 00221 struct _ScanLineList *next; /* next in the list */ 00222 } ScanLineList; 00223 00224 00225 typedef struct { 00226 int ymax; /* ymax for the polygon */ 00227 int ymin; /* ymin for the polygon */ 00228 ScanLineList scanlines; /* header node */ 00229 } EdgeTable; 00230 00231 00232 /* 00233 * Here is a struct to help with storage allocation 00234 * so we can allocate a big chunk at a time, and then take 00235 * pieces from this heap when we need to. 00236 */ 00237 #define SLLSPERBLOCK 25 00238 00239 typedef struct _ScanLineListBlock { 00240 ScanLineList SLLs[SLLSPERBLOCK]; 00241 struct _ScanLineListBlock *next; 00242 } ScanLineListBlock; 00243 00244 00245 00246 /* 00247 * 00248 * a few macros for the inner loops of the fill code where 00249 * performance considerations don't allow a procedure call. 00250 * 00251 * Evaluate the given edge at the given scanline. 00252 * If the edge has expired, then we leave it and fix up 00253 * the active edge table; otherwise, we increment the 00254 * x value to be ready for the next scanline. 00255 * The winding number rule is in effect, so we must notify 00256 * the caller when the edge has been removed so he 00257 * can reorder the Winding Active Edge Table. 00258 */ 00259 #define EVALUATEEDGEWINDING(pAET, pPrevAET, y, fixWAET) { \ 00260 if (pAET->ymax == y) { /* leaving this edge */ \ 00261 pPrevAET->next = pAET->next; \ 00262 pAET = pPrevAET->next; \ 00263 fixWAET = 1; \ 00264 if (pAET) \ 00265 pAET->back = pPrevAET; \ 00266 } \ 00267 else { \ 00268 BRESINCRPGONSTRUCT(pAET->bres); \ 00269 pPrevAET = pAET; \ 00270 pAET = pAET->next; \ 00271 } \ 00272 } 00273 00274 00275 /* 00276 * Evaluate the given edge at the given scanline. 00277 * If the edge has expired, then we leave it and fix up 00278 * the active edge table; otherwise, we increment the 00279 * x value to be ready for the next scanline. 00280 * The even-odd rule is in effect. 00281 */ 00282 #define EVALUATEEDGEEVENODD(pAET, pPrevAET, y) { \ 00283 if (pAET->ymax == y) { /* leaving this edge */ \ 00284 pPrevAET->next = pAET->next; \ 00285 pAET = pPrevAET->next; \ 00286 if (pAET) \ 00287 pAET->back = pPrevAET; \ 00288 } \ 00289 else { \ 00290 BRESINCRPGONSTRUCT(pAET->bres); \ 00291 pPrevAET = pAET; \ 00292 pAET = pAET->next; \ 00293 } \ 00294 }

Generated Mon Sep 6 21:58:16 2004.
Copyright © 1998-2003 by the respective authors.

This document is licensed under the terms of the GNU Free Documentation License and may be freely distributed under the conditions given by this license.