c++实现改进的有效边表算法

非常感谢您的提问，C知道可以为您提供有关改进的有效边表算法的实现方案。改进的有效边表算法是一种用于计算多边形的裁剪算法，它可以有效地减少计算量和内存占用。以下是一个简单的C语言实现示例：

#include <stdio.h>
#include <stdlib.h>

#define MAX_POINTS 100

typedef struct {
    float x, y;
} Point;

typedef struct {
    Point p1, p2;
} Edge;

typedef struct {
    int num_edges;
    Edge edges[MAX_POINTS];
} Polygon;

typedef struct {
    float x, y;
    int edge_num;
} Vertex;

typedef struct {
    int num_vertices;
    Vertex vertices[MAX_POINTS];
} ActiveEdgeTable;

void add_vertex(ActiveEdgeTable *aet, Edge *edge, int edge_num, float y) {
    float x;
    if (edge->p1.y == edge->p2.y) {
        return;
    }
    if (edge->p1.y < edge->p2.y) {
        x = edge->p1.x + (y - edge->p1.y) * (edge->p2.x - edge->p1.x) / (edge->p2.y - edge->p1.y);
    } else {
        x = edge->p2.x + (y - edge->p2.y) * (edge->p1.x - edge->p2.x) / (edge->p1.y - edge->p2.y);
    }
    aet->vertices[aet->num_vertices].x = x;
    aet->vertices[aet->num_vertices].y = y;
    aet->vertices[aet->num_vertices].edge_num = edge_num;
    aet->num_vertices++;
}

void remove_vertex(ActiveEdgeTable *aet, int i) {
    int j;
    for (j = i; j < aet->num_vertices - 1; j++) {
        aet->vertices[j] = aet->vertices[j+1];
    }
    aet->num_vertices--;
}

void update_aet(ActiveEdgeTable *aet, Polygon *polygon, float y) {
    int i;
    for (i = 0; i < polygon->num_edges; i++) {
        Edge *edge = &polygon->edges[i];
        if (edge->p1.y == edge->p2.y) {
            continue;
        }
        if (edge->p1.y == y) {
            add_vertex(aet, edge, i, y);
        }
    }
    for (i = 0; i < aet->num_vertices; i++) {
        Vertex *v = &aet->vertices[i];
        if (v->y == y) {
            remove_vertex(aet, i);
            i--;
        } else {
            v->x += (v->edge_num < polygon->num_edges / 2) ? 1 : -1;
        }
    }
}

void fill_scanline(ActiveEdgeTable *aet, float y) {
    int i;
    for (i = 0; i < aet->num_vertices; i += 2) {
        int x1 = aet->vertices[i].x;
        int x2 = aet->vertices[i+1].x;
        printf("(%d,%f)-(%d,%f)\n", x1, y, x2, y);
    }
}

void fill_polygon(Polygon *polygon) {
    int i;
    float y;
    ActiveEdgeTable aet = {0};
    for (y = 0.0; y < MAX_POINTS; y += 0.5) {
        update_aet(&aet, polygon, y);
        fill_scanline(&aet, y);
    }
}

int main() {
    Polygon polygon = {
        4,
        {
            {{50,50},{100,50}},
            {{100,50},{100,100}},
            {{100,100},{50,100}},
            {{50,100},{50,50}}
        }
    };
    fill_polygon(&polygon);
    return 0;
}

希望这个示例可以帮助您理解改进的有效边表算法的实现方式。如果您有任何其他问题，请随时问我。