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- Log ----------------------------------------------------------------- http://repo.or.cz/w/gfxprim.git/commit/96f86e4c8dfdbdea1a468aa29130010be8f89...
commit 96f86e4c8dfdbdea1a468aa29130010be8f89e27 Merge: 5534588 2ebe2ee Author: Jiri BlueBear Dluhos jiri.bluebear.dluhos@gmail.com Date: Mon Dec 10 14:10:24 2012 +0100
Merge branch 'master' of ssh://repo.or.cz/srv/git/gfxprim
http://repo.or.cz/w/gfxprim.git/commit/5534588fb5e3d02ee7504e01ce8b3f1045fba...
commit 5534588fb5e3d02ee7504e01ce8b3f1045fba7fd Author: Jiri BlueBear Dluhos jiri.bluebear.dluhos@gmail.com Date: Mon Dec 10 14:09:58 2012 +0100
Rewrote FillPolygon() according to books. Still not correct though.
diff --git a/libs/gfx/GP_Polygon.c b/libs/gfx/GP_Polygon.c index 2114006..b807d1c 100644 --- a/libs/gfx/GP_Polygon.c +++ b/libs/gfx/GP_Polygon.c @@ -26,6 +26,7 @@ #include <stdlib.h> #include <stdio.h> #include <math.h> +#include <limits.h>
#include "core/GP_Transform.h" #include "core/GP_GetPutPixel.h" @@ -34,166 +35,214 @@ #include "GP_HLine.h" #include "GP_Polygon.h"
-/* A single edge of the polygon. */ -struct GP_PolygonEdge { - float x1, y1, x2, y2; - float ymin, ymax; - float dx_by_dy; /* dx/dy (0 for horizontal edges) */ -}; +/* "almost equality" for float coordinates */ +#define GP_COORDS_ALMOST_EQUAL(a,b) (fabsf(a-b) < 0.00001f)
-/* Threshod value for delta y; edges with dy smaller than this are considered horizontal. */ -const float GP_HORIZ_DY_THRESHOLD = 0.00001f; +/* + * Edge state. Every edge proceeds from READY to ACTIVE and then FINISHED. + * Numeric values reflect sorting priority (ACTIVE < READY < FINISHED). + */ +#define EDGE_FINISHED 2 +#define EDGE_READY 1 +#define EDGE_ACTIVE 0 + +/* Working record about an edge. */ +struct GP_Edge { + int state; /* edge state */ + float x; /* X coordinate of the working point */ + int y; /* Y coordinate of the working point */ + int dy; /* vertical size */ + float dxy; /* dx/dy */ +};
-/* Initializes the polygon_edge structure. */ -static void GP_InitEdge(struct GP_PolygonEdge *edge, float x1, float y1, - float x2, float y2) +/* Initializes the edge structure. */ +static void GP_InitEdge(struct GP_Edge *e, GP_Coord x1, GP_Coord y1, + GP_Coord x2, GP_Coord y2) { - edge->x1 = x1; - edge->y1 = y1; - edge->x2 = x2; - edge->y2 = y2; - edge->ymin = fminf(edge->y1, edge->y2); - edge->ymax = fmaxf(edge->y1, edge->y2); - - /* horizontal (or almost horizontal) edges are a special case */ - if ((edge->ymax - edge->ymin) < GP_HORIZ_DY_THRESHOLD) { - edge->dx_by_dy = 0.0; /* not meaningful */ - return; + GP_ASSERT(y1 != y2, "horizontal edges not allowed here"); + + /* initialize the working point to the top point of the edge */ + if (y1 < y2) { + e->x = x1; + e->y = y1; + } else { + e->x = x2; + e->y = y2; }
- float dx = (edge->x2 - edge->x1); - float dy = (edge->y2 - edge->y1); - edge->dx_by_dy = dx / dy; + e->dy = GP_ABS(y2 - y1); + e->dxy = (float)(x2 - x1)/(y2 - y1); + e->state = EDGE_READY; }
-static int GP_IsEdgeHorizontal(struct GP_PolygonEdge *edge) -{ - return ((edge->ymax - edge->ymin) < GP_HORIZ_DY_THRESHOLD); -} +/* Type of a callback function to be passed to qsort(). */ +typedef int (*GP_SortCallback)(const void *, const void *);
-/* Computes an intersection of the specified scanline with the given edge. - * If successful, returns 1 and stores the resulting X coordinate into result_x. - * If failed (the edge does not intersect), 0 is returned. - * Horizontal edges are ignored at this point (result is always 0). +/* + * Compares two edges. Used for initial sorting of the edges. + * Edges are sorted by Y first, then by X, then by DXY. + * Returns -1 if e1<e2, +1 if e1>e2, 0 if e1==e2. */ -static int GP_ComputeIntersection(float *result_x, struct GP_PolygonEdge *edge, float y) +static int GP_CompareEdgesInitial(struct GP_Edge *e1, struct GP_Edge *e2) { - if (y<edge->ymin || y>edge->ymax) - return 0; /* outside the edge Y range */ + if (e1->y < e2->y) return -1; + if (e1->y > e2->y) return 1;
- if (GP_IsEdgeHorizontal(edge)) - return 0; /* ignore horizontal edges */ + if (e1->x < e2->x) return -1; + if (e1->x > e2->x) return 1;
- *result_x = edge->x1 + (y-edge->y1)*edge->dx_by_dy; + if (e1->dxy < e2->dxy) return -1; + if (e1->dxy > e2->dxy) return 1;
- return 1; + return 0; }
-/* Sorting callback. Compares two floats and returns -1 if A<B, - * +1 if A>B, 0 if they are equal. +/* + * Compares two edges. Used for in-run sorting. + * Edges are sorted by state (ACTIVE < READY < FINISHED), then by X, + * then by DXY. + * Returns -1 if e1<e2, +1 if e1>e2, 0 if e1==e2. */ -static int GP_CompareFloats(const void *ptr_a, const void *ptr_b) +static int GP_CompareEdgesRuntime(struct GP_Edge *e1, struct GP_Edge *e2) { - float a = ((float *) ptr_a)[0]; - float b = ((float *) ptr_b)[0]; + if (e1->state < e2->state) return -1; + if (e1->state > e2->state) return 1; + + if (e1->x < e2->x) return -1; + if (e1->x > e2->x) return 1; + + if (e1->dxy < e2->dxy) return -1; + if (e1->dxy > e2->dxy) return 1;
- if (a < b) return -1; - if (a > b) return 1; return 0; }
-/* Computes intersections of the y coordinate with all edges, - * writing the X coordinates of the intersections, sorted by X coordinate, - * into 'results'. - */ -static int GP_ComputeScanline(float *results, struct GP_PolygonEdge *edges, - size_t count, float y) -{ - unsigned int edge_index = 0; - int result_index = 0; - - for (; edge_index<count; edge_index++) { +typedef struct { + GP_Coord x, y; +} GP_Point;
- struct GP_PolygonEdge *edge = edges + edge_index; - float x; +void GP_FillPolygon_Raw(GP_Context *context, unsigned int nvert, + const GP_Coord *xy, GP_Pixel pixel) +{ + unsigned int i; + struct GP_Edge *e; + + if (nvert < 3) + return; /* not enough vertices */ + + GP_Point const *vert = (GP_Point const *) xy; + + /* find first and last scanline */ + GP_Coord ymin = INT_MAX, ymax = -INT_MAX; + for (i = 0; i < nvert; i++) { + ymax = GP_MAX(ymax, vert[i].y); + ymin = GP_MIN(ymin, vert[i].y); + } + + /* build a list of edges */ + struct GP_Edge edges[nvert]; + unsigned int nedges = 0; /* number of edges in list */ + for (i = 0; i < nvert; i++) {
/* - * Horizontal edges match either as a whole (yielding two - * intersections), or not at all. + * next vertex index (wraps to 0 at end to connect + * the last vertex with the first one) */ - if (GP_IsEdgeHorizontal(edge)) { - if (fabsf(edge->ymin - y) < 0.00001f) { - results[result_index++] = GP_MIN(edge->x1, edge->x2); - results[result_index++] = GP_MAX(edge->x1, edge->x2); - } + unsigned int nexti = (i+1) % nvert; + + /* skip horizontal edges */ + if (vert[i].y == vert[nexti].y) { continue; }
- if (GP_ComputeIntersection(&x, edge, y)) { - results[result_index++] = x; - } + GP_InitEdge(edges + nedges, + vert[i].x, vert[i].y, + vert[nexti].x, vert[nexti].y); + e = edges + nedges; + + nedges++; }
- qsort(results, result_index, sizeof(float), GP_CompareFloats); - - return result_index; -} - -void GP_FillPolygon_Raw(GP_Context *context, unsigned int vertex_count, - const GP_Coord *xy, GP_Pixel pixel) -{ - float ymin = HUGE_VALF, ymax = -HUGE_VALF; - struct GP_PolygonEdge *edge; - struct GP_PolygonEdge edges[2*vertex_count]; - - - /* Build edge structures for each vertex-vertex connection. - * NOTE: Each vertex is in fact in the middle of the pixel, so - * add 0.5 to both coordinates. - */ - int i; - for (i = 0; i < (int)vertex_count - 1; i++) { - edge = edges + i; - GP_InitEdge(edge, - 0.5f + xy[2*i], 0.5f + xy[2*i + 1], - 0.5f + xy[2*i + 2], 0.5f + xy[2*i + 3]); - ymin = fminf(ymin, edge->ymin); - ymax = fmaxf(ymax, edge->ymax); + if (nedges < 2) + return; /* not really a polygon */ + + for (i = 1; i < nedges; i++) { + e = edges + i; + struct GP_Edge *prev_e = edges + i - 1; + if (GP_COORDS_ALMOST_EQUAL(prev_e->x + prev_e->dy*prev_e->dxy, e->x)) { + prev_e->dy--; + } + else if (GP_COORDS_ALMOST_EQUAL(e->x + e->dy*e->dxy, prev_e->x)) { + e->dy--; + } }
- /* the last edge (from the last point to the first one) */ - edge = edges + vertex_count - 1; - GP_InitEdge(edge, - 0.5f + xy[2*i], 0.5f + xy[2*i + 1], - 0.5f + xy[0], 0.5f + xy[1]); + /* initially sort edges by Y, then X */ + qsort(edges, nedges, sizeof(struct GP_Edge), + (GP_SortCallback) GP_CompareEdgesInitial);
- /* For each scanline, compute intersections with all edges + for (i = 0; i < nedges; i++) { + e = edges + i; + } + + /* + * for each scanline, compute intersections with all edges * and draw a horizontal line segment between the intersections. */ - float intersections[vertex_count]; - int y; - for (y = (int) ymin; y <= (int) ymax; y++) { - int inter_count = GP_ComputeScanline(intersections, edges, vertex_count, y + 0.5f); - - i = 0; - for (;;) { - if (i >= inter_count) break; - float start = intersections[i++]; - if (i >= inter_count) { - - /* a solo vertex or a single-point intersection */ - GP_PutPixel_Raw(context, start, y, pixel); - break; + float inter[nedges]; + unsigned int ninter; + int y = ymin; + for (y = ymin; y <= ymax; y++) { + + /* mark edges we have just reached as active */ + for (i = 0; i < nedges; i++) { + e = edges + i; + if (e->state == EDGE_READY && (y == e->y)) { + e->state = EDGE_ACTIVE; } - float end = intersections[i++]; - if (start == end) { - - /* two intersections - edge joint */ - if (i >= inter_count) break; - end = intersections[i++]; + } + qsort(edges, nedges, sizeof(struct GP_Edge), + (GP_SortCallback) GP_CompareEdgesRuntime); + + /* record intersections with active edges */ + ninter = 0; + for (i = 0; i < nedges; i++) { + e = edges + i; + if (e->state == EDGE_ACTIVE) { + inter[ninter++] = e->x; } + } + + /* draw each even range between intersections */ + for (i = 0; i < ninter; i += 2) { + float start = inter[i]; + + /* odd number of intersections - skip last */ + if (i+1 == ninter) + break; + + float end = inter[i+1]; GP_HLine_Raw(context, start, end, y, pixel); } + + /* check and mark edges we are done with */ + for (i = 0; i < nedges; i++) { + e = edges + i; + if (e->state == EDGE_ACTIVE && e->dy == 0) { + e->state = EDGE_FINISHED; + } + } + qsort(edges, nedges, sizeof(struct GP_Edge), + (GP_SortCallback) GP_CompareEdgesRuntime); + + /* update active edges for next step */ + for (i = 0; i < nedges; i++) { + e = edges + i; + if (e->state == EDGE_ACTIVE) { + e->x += e->dxy; + e->dy--; + } + } } }
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Summary of changes: libs/gfx/GP_Polygon.c | 291 ++++++++++++++++++++++++++++-------------------- 1 files changed, 170 insertions(+), 121 deletions(-)
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