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/*
MultiBezier.C
Code by 523066680, 2016-09-27
523066680@163.com
*/
#include <GL/glut.h>
#include <stdio.h>
#include <time.h>
#include <unistd.h>
#include <math.h>
//窗口尺寸
#define SIZE_X 500
#define SIZE_Y 500
const double PI = 3.14159265;
const double PI2 = 3.14159265 * 2;
#define LINES 20
#define PARTS 50
#define CP_PARTS 50
#define CP_STEP 1.0/CP_PARTS
// LINES 积累的线的数量,而非细分数量
// PARTS 单条曲线细分的数量
// CP_PARTS 控制点移动轨迹的细分量
typedef struct
{
float x;
float y;
}
point;
typedef struct
{
point cp[4];
float index;
}
ControlPoint;
point MultiLine[LINES][PARTS];
int winID;
// PointOnCubicBeizer Function, copy from:
// https://zh.wikipedia.org/wiki/貝茲曲線
point PointOnCubicBeizer(point cp[4], float t)
{
float cx, bx, ax, cy, by, ay;
float tSquared, tCubed;
point result;
cx = 3.0 * (cp[1].x - cp[0].x);
bx = 3.0 * (cp[2].x - cp[1].x) - cx;
ax = cp[3].x - cp[0].x - cx - bx;
cy = 3.0 * (cp[1].y - cp[0].y);
by = 3.0 * (cp[2].y - cp[1].y) - cy;
ay = cp[3].y - cp[0].y - cy - by;
tSquared = t * t;
tCubed = tSquared * t;
result.x = ((ax * tCubed) + (bx * tSquared) + (cx * t) + cp[0].x);
result.y = ((ay * tCubed) + (by * tSquared) + (cy * t) + cp[0].y);
return result;
}
void display(void)
{
glBegin(GL_POINTS);
glColor4f(0.3, 0.5, 0.8, 0.4);
for (int i = 0; i < LINES; i++)
{
for (int j = 0; j < PARTS; j++)
{
glVertex3f(MultiLine[i][j].x, MultiLine[i][j].y, 0.0);
}
}
glEnd();
glutSwapBuffers();
}
//闲时回调函数,主要负责计算、延时
void idle(void)
{
//临时坐标变量
point coord;
//主控制点,通过PointOnCubicBeizer函数和cp[4]数据获取坐标
point MainCp[4];
static int MainIdx = 0;
//ControlPoint 结构包含 控制点、曲线进度信息
static ControlPoint cp[4] =
{
0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0,
0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0,
0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0,
0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0,
};
glBlendFunc(GL_SRC_ALPHA, GL_DST_ALPHA);
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
glPushMatrix();
//4个控制点的变化和进度
for (int i = 0; i < 4; i++)
{
cp[i].index += CP_STEP;
//index超过1.0时重新设定控制点
if (cp[i].index >= 1.0)
{
//上一个终点作为新的起点
cp[i].cp[0].x = cp[i].cp[3].x;
cp[i].cp[0].y = cp[i].cp[3].y;
//使第一控制点与上次曲线对称(减少尖突的情况)
cp[i].cp[1].x = cp[i].cp[3].x + (cp[i].cp[3].x - cp[i].cp[2].x);
cp[i].cp[1].y = cp[i].cp[3].y + (cp[i].cp[3].y - cp[i].cp[2].y);
//后面两个点随机
for (int ii = 2; ii < 4; ii++)
{
cp[i].cp[ii].x = (float) ( rand() % 500 - 250);
cp[i].cp[ii].y = (float) ( rand() % 500 - 250);
}
//从1单位的CP_STEP开始,而非0.0,避免重合显示
cp[i].index = CP_STEP;
}
coord = PointOnCubicBeizer( cp[i].cp, cp[i].index );
MainCp[i].x = coord.x;
MainCp[i].y = coord.y;
}
//当前曲线坐标写入数组
for (int i = 0; i < PARTS; i++)
{
coord = PointOnCubicBeizer(MainCp , (float)i / (float)PARTS );
MultiLine[MainIdx][i].x = coord.x;
MultiLine[MainIdx][i].y = coord.y;
}
//线条序号,达到数组末端时回到 0
if ( MainIdx >= (LINES - 1) )
{
MainIdx = 0;
}
else
{
MainIdx++;
}
usleep(30000);
glutPostRedisplay();
}
//窗口事件响应函数
void reshape(int Width,int Height)
{
const float fa = 32.0;
const float half = 250.0;
if (Width == Height)
{
//视口范围
glViewport(0, 0, Width, Height);
}
else if ( Width > Height )
{
glViewport(0, 0, Height, Height);
}
else
{
glViewport(0, 0, Width, Width);
}
//投影视图矩阵
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-half, half, -half, half, 0.0, 100.0);
// 模型视图矩阵
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(0.0,0.0,fa, 0.0,0.0,0.0, 0.0,1.0,fa);
// 观察点, 朝向的坐标, 正上方朝向
}
//按键响应
void keypress(unsigned char key, int mousex, int mousey)
{
switch (key)
{
case 'q':
glutDestroyWindow(winID);
exit(0);
break;
case 'Q':
glutDestroyWindow(winID);
exit(0);
break;
}
}
void init(void)
{
glClearColor(0.0, 0.0, 0.0, 0.0);
glLineWidth( 2.0 );
glPointSize( 6.0 );
//glEnable(GL_DEPTH_TEST); //开启深度缓冲
glEnable(GL_BLEND); //开启颜色混合
glEnable(GL_POINT_SMOOTH); //点平滑
glEnable(GL_LINE_SMOOTH); //线平滑
srand(time(NULL));
for (int i = 0; i < 10; i++)
{
for (int j = 0; j < 10; j++)
{
MultiLine[i][j].x = 0.0;
MultiLine[i][j].y = 0.0;
}
}
}
void main(int argc, char *argv[])
{
glutInit(&argc, argv);
//显示模式 双缓冲 RGBA 深度缓冲
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH );
glutInitWindowSize(SIZE_X, SIZE_Y); //窗口大小
glutInitWindowPosition(200, 200); //位置
winID = glutCreateWindow("MultiBezier"); //窗口句柄
init();
glutDisplayFunc(display); //显示
glutKeyboardFunc(keypress); //按键事件响应
glutReshapeFunc(reshape); //窗口事件响应
glutIdleFunc(idle); //闲时回调函数
glutMainLoop(); //开始主循环
}
编译指令:
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gcc -std=c11 "%1" -o "%~n1" ^
-ID:\OGL\freeglut-MinGW-3.0.0-1.mp\include ^
-LD:\OGL\freeglut-MinGW-3.0.0-1.mp\lib\x64 ^
-lfreeglut -lopengl32 -lglu32