mfc + opengl 画三角形怎么看不到三角形呀！

Question

我用mfc + opengl 画三角形
代码如下:
怎么只能看到黑屏,却看不见三角形
void CTes1View::DrawScene()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // 清除屏幕及深度缓存
glLoadIdentity(); // 重置视口glTranslatef(-1.5f,0.0f,-6.0f); // 左移 1.5 单位，并移入屏幕 6.0glBegin(GL_TRIANGLES); // 绘制三角形glVertex3f( 0.0f, 1.0f, 0.0f); // 上顶点glVertex3f(-1.0f,-1.0f, 0.0f); // 左下glVertex3f( 1.0f,-1.0f, 0.0f); // 右下
glEnd(); // 三角形绘制结束 glFinish();
}

Answer 1

glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // 清除屏幕及深度缓存
glLoadIdentity(); // 重置视口glColor4f(1.0f, 1.0f, 1.0f, 1.0f);glTranslatef(-1.5f,0.0f,-6.0f); // 左移 1.5 单位，并移入屏幕 6.0glBegin(GL_TRIANGLES); // 绘制三角形glVertex3f( 0.0f, 1.0f, 0.0f); // 上顶点glVertex3f(-1.0f,-1.0f, 0.0f); // 左下glVertex3f( 1.0f,-1.0f, 0.0f); // 右下
glEnd(); // 三角形绘制结束 glFinish();

Answer 2

nehe教程学习变换矩阵的用途注意相机的位置， 在你的设置下，三角形很可能是在相机可视的范围外呢#include <e:/opengl/include/gl/glut.h>
#include <stdlib.h>void init (void)
{
glClearColor(0.0, 1.0, 0.0,0.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(70.0, 1.0, 1, 1000);
gluLookAt(0.0,500.0,0.0, 0.0,0.0,0.0, 1.0,0.0,0.0);
}
// ball statevoid display(void)
{
glClear(GL_COLOR_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

glBegin(GL_POLYGON);
glNormal3d(0, -1, 0);
glColor3f(0.0,0.0,1.0);
glVertex3f(100, 0,  100);
    glVertex3f(100, 0, -100);
    glVertex3f(-100,0, -100);
    glVertex3f(-100,0,  100);
    glEnd();
glFlush();
}int main(int argc,char **argv)
{
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
glutInitWindowSize(500,500);
glutInitWindowPosition(100,100);
glutCreateWindow(argv[0]);
init();
glutDisplayFunc(display);
glutMainLoop();
return 0;
}

Answer 3

对于你的例子，把gluLookAt修改为
gluLookAt(0,0,0,   0,0,-1,  0,1,0)；就可以了
把你的代码移动到display函数里面，保留前面glMatrixMode(...)；那两行就可以了