OpenGL gluLookAt

Question

我试着画一个茶壶，并在3D中查看它，但当我运行程序时，什么也没有显示出来。窗子里什么也没有。我知道这与我的gluLookAt()函数有关，但我不确定如何修复它。

// helloteapot.cc

//#include <GLUT/gl.h>
#include <GLUT/glut.h>
#include "GL/glui.h"

void display () {

/* clear window */
glClear(GL_COLOR_BUFFER_BIT);

/* draw scene */
glColor3f(1.0, 0.0, 0.0);
glTranslatef(0.0, 0.5, 0.0);
glutSolidTeapot(0.15);

/* flush drawing routines to the window */
glFlush();

}

int main ( int argc, char * argv[] ) {
glutInit(&argc,argv);

/* setup the size, position, and display mode for new windows */
glutInitWindowSize(800,600);
glutInitWindowPosition(0,0);
glutInitDisplayMode(GLUT_RGB);

/* create and set up a window */
glutCreateWindow("hello, teapot!");

glutDisplayFunc(display);

/*GLfloat width = 800;
GLfloat height = 600;
GLfloat aspect = (GLfloat)width / (GLfloat)height;

// Set the viewport to cover the new window
glViewport(0, 0, width, height);*/

// Set the aspect ratio of the clipping volume to match the 
viewport
glMatrixMode(GL_PROJECTION);  // To operate on the Projection 
matrix
glLoadIdentity();             // Reset
// Enable perspective projection with fovy, aspect, zNear and zFar
//luPerspective(45.0f, aspect, -100.0f, 100.0f);
gluLookAt(0, 0, 0, 0, 0.5, 0, 0, -1, 0);

/* tell GLUT to wait for events */
glutMainLoop();
}

Answer 1

您已经要求GL将摄影机定位在原点，将摄影机向上对准(0，0.5，0)点，并且还(错误地)将上方向向量指定为0，-1，0。问题是摄影机的前进方向是由眼睛和目标位置指定的(0，1，0)，并且该方向与上方向向量或(0，-1，0)冲突。尝试使用与正向成直角的向量！(例如1，0，0，0，0，0，1)

gluLookAt(
  0, 0, 0,   //< camera location
  0, 0.5, 0, //< looking towards point
  1, 0, 0);  //< which direction is up?