使用vc++6.0和opengl通过导入dem数据绘制TIN的代码

以下是使用VC++6.0和OpenGL绘制TIN的代码示例，其中包括导入DEM数据、生成TIN三角网格、绘制三角形等部分：

#include <GL/gl.h>
#include <GL/glu.h>
#include <stdio.h>
#include <stdlib.h>

#define MAX_POINTS      1000000
#define MAX_TRIANGLES  1000000

// 定义点和三角形结构体
typedef struct {
    double x, y, z;
} Point;

typedef struct {
    int v1, v2, v3;
} Triangle;

// 定义全局变量
int num_points = 0;
Point points[MAX_POINTS];

int num_triangles = 0;
Triangle triangles[MAX_TRIANGLES];

// 读取DEM数据
void readDEM(const char *filename) {
    FILE *fp = fopen(filename, "r");
    if (!fp) {
        printf("Cannot open file: %s\n", filename);
        exit(1);
    }

    // 读取点坐标
    while (fscanf(fp, "%lf%lf%lf", &points[num_points].x, &points[num_points].y, &points[num_points].z) == 3) {
        num_points++;
        if (num_points >= MAX_POINTS) {
            printf("Too many points.\n");
            exit(1);
        }
    }

    fclose(fp);
}

// 生成TIN三角网格
void generateTIN() {
    // 添加3个初始点
    triangles[0].v1 = 0;
    triangles[0].v2 = 1;
    triangles[0].v3 = 2;
    num_triangles = 1;

    // 逐个添加点并更新三角形
    for (int i = 3; i < num_points; i++) {
        Point p = points[i];

        // 查找包含点p的三角形
        for (int j = 0; j < num_triangles; j++) {
            Triangle t = triangles[j];
            Point p1 = points[t.v1];
            Point p2 = points[t.v2];
            Point p3 = points[t.v3];

            // 判断点p是否在三角形t内
            double d1 = (p.x - p1.x) * (p2.y - p1.y) - (p.y - p1.y) * (p2.x - p1.x);
            double d2 = (p.x - p2.x) * (p3.y - p2.y) - (p.y - p2.y) * (p3.x - p2.x);
            double d3 = (p.x - p3.x) * (p1.y - p3.y) - (p.y - p3.y) * (p1.x - p3.x);

            if (d1 >= 0 && d2 >= 0 && d3 >= 0) {
                // 点p在三角形t内，将t的三条边删除并添加3个新三角形
                triangles[j] = triangles[num_triangles - 1];
                num_triangles--;

                triangles[num_triangles].v1 = t.v1;
                triangles[num_triangles].v2 = t.v2;
                triangles[num_triangles].v3 = i;
                num_triangles++;

                triangles[num_triangles].v1 = t.v2;
                triangles[num_triangles].v2 = t.v3;
                triangles[num_triangles].v3 = i;
                num_triangles++;

                triangles[num_triangles].v1 = t.v3;
                triangles[num_triangles].v2 = t.v1;
                triangles[num_triangles].v3 = i;
                num_triangles++;

                break;
            }
        }
    }
}

// 绘制三角形
void drawTriangle(int i) {
    glBegin(GL_TRIANGLES);
    glColor3f(1.0f, 1.0f, 1.0f);
    glVertex3f(points[triangles[i].v1].x, points[triangles[i].v1].y, points[triangles[i].v1].z);
    glVertex3f(points[triangles[i].v2].x, points[triangles[i].v2].y, points[triangles[i].v2].z);
    glVertex3f(points[triangles[i].v3].x, points[triangles[i].v3].y, points[triangles[i].v3].z);
    glEnd();
}

// 绘制TIN三角网格
void drawTIN() {
    glPointSize(2.0f);
    glBegin(GL_POINTS);
    glColor3f(0.0f, 1.0f, 0.0f);
    for (int i = 0; i < num_points; i++) {
        glVertex3f(points[i].x, points[i].y, points[i].z);
    }
    glEnd();

    glLineWidth(1.0f);
    for (int i = 0; i < num_triangles; i++) {
        drawTriangle(i);
    }
}

// 初始化OpenGL环境
void init() {
    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
    glMatrixMode(GL_PROJECTION);
    gluPerspective(45.0, 1.0, 1.0, 1000.0);
    glMatrixMode(GL_MODELVIEW);
    gluLookAt(0.0, 0.0, 100.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
}

// 显示回调函数
void display() {
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glPushMatrix();
    drawTIN();
    glPopMatrix();

    glutSwapBuffers();
}

// 窗口大小改变回调函数
void reshape(int w, int h) {
    glViewport(0, 0, w, h);
}

int main(int argc, char **argv) {
    if (argc < 2) {
        printf("Usage: %s demfile\n", argv[0]);
        return 1;
    }

    readDEM(argv[1]);
    generateTIN();

    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH);
    glutInitWindowSize(640, 480);
    glutCreateWindow("TIN Viewer");

    init();

    glutDisplayFunc(display);
    glutReshapeFunc(reshape);

    glutMainLoop();

    return 0;
}

其中，`readDEM`函数用于读取DEM数据，`generateTIN`函数用于生成TIN三角网格，`drawTriangle`函数用于绘制单个三角形，`drawTIN`函数用于绘制整个TIN三角网格，`init`函数用于初始化OpenGL环境，`display`函数用于绘制回调，`reshape`函数用于窗口大小改变回调。在主函数中，先调用`readDEM`和`generateTIN`函数生成TIN三角网格，然后使用glut创建窗口并注册回调函数，最后进入主循环等待事件。