opengl實現(xiàn)任意兩點間畫圓柱體

2020-01-26 13:41:04

字體：大中小

來源：轉(zhuǎn)載

供稿：網(wǎng)友

本文實例為大家分享了opengl實現(xiàn)任意兩點間畫圓柱體的具體代碼，供大家參考，具體內(nèi)容如下

1、問題提出

兩點間畫線簡單：

glBegin(GL_LINES); //注意是LINES不是LINE，這個錯誤一定要注意。

glVertexf(x1, y1, z1);

glVertexf(x2, y2, z2);

glEnd();

畫線函數(shù)不會影響opengl的矩陣堆棧。

但是很多時候線條效果會比較差，比如我要做一個骨骼動畫，關(guān)節(jié)點間的骨頭用線條太難看，即使使用glLineWidth設(shè)置線寬，視覺效果還是一塌糊涂。還有利用分形繪制3D樹的時候，樹干用線條（寬線條）繪制效果也不佳。所以此時需要實現(xiàn)一個函數(shù)，3D空間中任意兩點間用幾何體繪制，我下面介紹一種思路。

2、原理介紹

要在A(x1,y1,z1), B(x2,y2,z2)之間繪制圓柱體，首先在原點處，沿著Y軸方向完成幾何體繪制，然后旋轉(zhuǎn)到AB向量方向，最后平移到A點處。關(guān)鍵在旋轉(zhuǎn)矩陣的計算，使用向量叉乘：AB向量和Y軸單位向量叉乘計算出右手side向量，然后side單位化，side和AB叉乘計算出最終的up方向。

代碼如下：

void RenderBone(float x0, float y0, float z0, float x1, float y1, float z1 ) {   GLdouble dir_x = x1 - x0;   GLdouble dir_y = y1 - y0;   GLdouble dir_z = z1 - z0;   GLdouble bone_length = sqrt( dir_x*dir_x + dir_y*dir_y + dir_z*dir_z );   static GLUquadricObj * quad_obj = NULL;   if ( quad_obj == NULL )     quad_obj = gluNewQuadric();   gluQuadricDrawStyle( quad_obj, GLU_FILL );   gluQuadricNormals( quad_obj, GLU_SMOOTH );   glPushMatrix();   // 平移到起始點   glTranslated( x0, y0, z0 );   // 計算長度   double length;   length = sqrt( dir_x*dir_x + dir_y*dir_y + dir_z*dir_z );   if ( length < 0.0001 ) {      dir_x = 0.0; dir_y = 0.0; dir_z = 1.0; length = 1.0;   }   dir_x /= length; dir_y /= length; dir_z /= length;   GLdouble up_x, up_y, up_z;   up_x = 0.0;   up_y = 1.0;   up_z = 0.0;   double side_x, side_y, side_z;   side_x = up_y * dir_z - up_z * dir_y;   side_y = up_z * dir_x - up_x * dir_z;   side_z = up_x * dir_y - up_y * dir_x;   length = sqrt( side_x*side_x + side_y*side_y + side_z*side_z );   if ( length < 0.0001 ) {     side_x = 1.0; side_y = 0.0; side_z = 0.0; length = 1.0;   }   side_x /= length; side_y /= length; side_z /= length;   up_x = dir_y * side_z - dir_z * side_y;   up_y = dir_z * side_x - dir_x * side_z;   up_z = dir_x * side_y - dir_y * side_x;   // 計算變換矩陣   GLdouble m[16] = { side_x, side_y, side_z, 0.0,     up_x,  up_y,  up_z,  0.0,     dir_x, dir_y, dir_z, 0.0,     0.0,  0.0,  0.0,  1.0 };   glMultMatrixd( m );   // 圓柱體參數(shù)   GLdouble radius= 20;    // 半徑   GLdouble slices = 8.0;   // 段數(shù)   GLdouble stack = 3.0;    // 遞歸次數(shù)   gluCylinder( quad_obj, radius, radius, bone_length, slices, stack );    glPopMatrix(); }

上面的代碼繪制圓柱體使用了glu幾何庫，如果繪制其他幾何體：比如四棱錐，或其它幾何體，只需要修改下面的框架：

void RenderBone(float x0, float y0, float z0, float x1, float y1, float z1 ) {   GLdouble dir_x = x1 - x0;   GLdouble dir_y = y1 - y0;   GLdouble dir_z = z1 - z0;   GLdouble bone_length = sqrt( dir_x*dir_x + dir_y*dir_y + dir_z*dir_z );   glPushMatrix();   // 平移到起始點   glTranslated( x0, y0, z0 );   // 計算長度   double length;   length = sqrt( dir_x*dir_x + dir_y*dir_y + dir_z*dir_z );   if ( length < 0.0001 ) {      dir_x = 0.0; dir_y = 0.0; dir_z = 1.0; length = 1.0;   }   dir_x /= length; dir_y /= length; dir_z /= length;   GLdouble up_x, up_y, up_z;   up_x = 0.0;   up_y = 1.0;   up_z = 0.0;   double side_x, side_y, side_z;   side_x = up_y * dir_z - up_z * dir_y;   side_y = up_z * dir_x - up_x * dir_z;   side_z = up_x * dir_y - up_y * dir_x;   length = sqrt( side_x*side_x + side_y*side_y + side_z*side_z );   if ( length < 0.0001 ) {     side_x = 1.0; side_y = 0.0; side_z = 0.0; length = 1.0;   }   side_x /= length; side_y /= length; side_z /= length;   up_x = dir_y * side_z - dir_z * side_y;   up_y = dir_z * side_x - dir_x * side_z;   up_z = dir_x * side_y - dir_y * side_x;   // 計算變換矩陣   GLdouble m[16] = { side_x, side_y, side_z, 0.0,     up_x,  up_y,  up_z,  0.0,     dir_x, dir_y, dir_z, 0.0,     0.0,  0.0,  0.0,  1.0 };   glMultMatrixd( m );      // 原點處向Y軸方向繪制幾何體   renderGeometryInYAxis();   glPopMatrix(); }

注意上面的renderGeometryInYAxis();必須是在Y軸上繪制幾何體。

3、測試代碼：

#include <gl/glut.h> #include <cstdio> #include <cstdlib> #include <cmath> void  init(void); void  reshape(int w,int h); void  display(void);  void RenderBone(float x0, float y0, float z0, float x1, float y1, float z1 ); int main(int argc, char** argv) {   glutInit(&argc, argv);   glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);    glutInitWindowSize (500, 500);   glutInitWindowPosition (100, 100);   glutCreateWindow("Sphere");   init ();   glutReshapeFunc(reshape);   glutDisplayFunc(display);   glutMainLoop();   return 0; } void init (void) {    glClearColor (0.0, 0.0, 0.0, 0.0);   glClearDepth(1);   glShadeModel(GL_SMOOTH);   GLfloat _ambient[]={1.0,1.0,1.0,1.0};   GLfloat _diffuse[]={1.0,1.0,0.0,1.0};   GLfloat _specular[]={1.0,1.0,1.0,1.0};   GLfloat _position[]={200,200,200,0};   glLightfv(GL_LIGHT0,GL_AMBIENT,_ambient);   glLightfv(GL_LIGHT0,GL_DIFFUSE,_diffuse);   glLightfv(GL_LIGHT0,GL_SPECULAR,_specular);   glLightfv(GL_LIGHT0,GL_POSITION,_position);   glEnable(GL_TEXTURE_2D);   glEnable(GL_LIGHTING);   glEnable(GL_LIGHT0);   glEnable(GL_DEPTH_TEST);   glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST); } void reshape(int w, int h) {   glViewport (0, 0, (GLsizei) w, (GLsizei) h);   glMatrixMode(GL_PROJECTION);   glLoadIdentity();   glOrtho(0.0, 500, 0.0, 500, -500, 500);   glMatrixMode(GL_MODELVIEW);   glLoadIdentity(); } void display(void) {   glMatrixMode(GL_MODELVIEW);   glLoadIdentity();   glClear (GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);   glPushMatrix();   {     RenderBone(100, 100, 100, 200, 300, 500);   } glPopMatrix();    glFlush();   glutPostRedisplay(); } void RenderBone(float x0, float y0, float z0, float x1, float y1, float z1 ) {   GLdouble dir_x = x1 - x0;   GLdouble dir_y = y1 - y0;   GLdouble dir_z = z1 - z0;   GLdouble bone_length = sqrt( dir_x*dir_x + dir_y*dir_y + dir_z*dir_z );   static GLUquadricObj * quad_obj = NULL;   if ( quad_obj == NULL )     quad_obj = gluNewQuadric();   gluQuadricDrawStyle( quad_obj, GLU_FILL );   gluQuadricNormals( quad_obj, GLU_SMOOTH );   glPushMatrix();   // 平移到起始點   glTranslated( x0, y0, z0 );   // 計算長度   double length;   length = sqrt( dir_x*dir_x + dir_y*dir_y + dir_z*dir_z );   if ( length < 0.0001 ) {      dir_x = 0.0; dir_y = 0.0; dir_z = 1.0; length = 1.0;   }   dir_x /= length; dir_y /= length; dir_z /= length;   GLdouble up_x, up_y, up_z;   up_x = 0.0;   up_y = 1.0;   up_z = 0.0;   double side_x, side_y, side_z;   side_x = up_y * dir_z - up_z * dir_y;   side_y = up_z * dir_x - up_x * dir_z;   side_z = up_x * dir_y - up_y * dir_x;   length = sqrt( side_x*side_x + side_y*side_y + side_z*side_z );   if ( length < 0.0001 ) {     side_x = 1.0; side_y = 0.0; side_z = 0.0; length = 1.0;   }   side_x /= length; side_y /= length; side_z /= length;   up_x = dir_y * side_z - dir_z * side_y;   up_y = dir_z * side_x - dir_x * side_z;   up_z = dir_x * side_y - dir_y * side_x;   // 計算變換矩陣   GLdouble m[16] = { side_x, side_y, side_z, 0.0,     up_x,  up_y,  up_z,  0.0,     dir_x, dir_y, dir_z, 0.0,     0.0,  0.0,  0.0,  1.0 };   glMultMatrixd( m );   // 圓柱體參數(shù)   GLdouble radius= 20;    // 半徑   GLdouble slices = 8.0;   // 段數(shù)   GLdouble stack = 3.0;    // 遞歸次數(shù)   gluCylinder( quad_obj, radius, radius, bone_length, slices, stack );    glPopMatrix(); }

最終效果圖：