gluProject() 的奇怪结果
Weird Result with gluProject()
我的 gluProject
函数 (OpenGL) 有问题。
我想将一个简单的 3D 点从对象 space 转换到屏幕 space。
我的代码如下:
int main(){
GLdouble mvmatrix[16];
GLdouble projmatrix[16];
GLint viewport[4];
GLdouble winx;
GLdouble winy;
GLdouble winz;
glGetDoublev(GL_MODELVIEW_MATRIX, mvmatrix);
glGetDoublev(GL_PROJECTION_MATRIX, projmatrix);
glGetIntegerv(GL_VIEWPORT, viewport);
gluProject(0.0, 0.0, 0.0, mvmatrix, projmatrix, viewport, &winx, &winy, &winz);
std::cout << winx << winy;
getchar();
getchar();
return 0;
}
输出为:
-1.71799e+009 -1.71799e+009
这是一个奇怪的结果,对我来说没有意义。
有谁知道出了什么问题?我没有在网上找到任何东西。
Does anyone know what went wrong?
您尚未创建 GL context 并在使用 glGetDoublev()
和 glGetIntegerv()
之前将其设为当前:
In order for any OpenGL commands to work, a context must be current; all OpenGL commands affect the state of whichever context is current. The current context is a thread-local variable, so a single process can have several threads, each of which has its own current context. However, a single context cannot be current in multiple threads at the same time.
您可以使用 (Free)GLUT (among other things (not exhaustive)) 创建一个 window 和关联的 GL 上下文:
#include <GL/glut.h>
#include <iostream>
int main(int argc, char **argv)
{
// create context & make it current
glutInit( &argc, argv );
glutInitWindowSize( 200, 200 );
glutInitDisplayMode( GLUT_RGBA );
glutCreateWindow( "GLUT" );
GLdouble mvmatrix[16];
GLdouble projmatrix[16];
GLint viewport[4];
GLdouble winx;
GLdouble winy;
GLdouble winz;
glGetDoublev( GL_MODELVIEW_MATRIX, mvmatrix );
glGetDoublev( GL_PROJECTION_MATRIX, projmatrix );
glGetIntegerv( GL_VIEWPORT, viewport );
gluProject
(
0.0, 0.0, 0.0,
mvmatrix, projmatrix, viewport,
&winx, &winy, &winz
);
std::cout << winx << " " << winy << std::endl;
return 0;
}
输出:
100 100
我的 gluProject
函数 (OpenGL) 有问题。
我想将一个简单的 3D 点从对象 space 转换到屏幕 space。
我的代码如下:
int main(){
GLdouble mvmatrix[16];
GLdouble projmatrix[16];
GLint viewport[4];
GLdouble winx;
GLdouble winy;
GLdouble winz;
glGetDoublev(GL_MODELVIEW_MATRIX, mvmatrix);
glGetDoublev(GL_PROJECTION_MATRIX, projmatrix);
glGetIntegerv(GL_VIEWPORT, viewport);
gluProject(0.0, 0.0, 0.0, mvmatrix, projmatrix, viewport, &winx, &winy, &winz);
std::cout << winx << winy;
getchar();
getchar();
return 0;
}
输出为:
-1.71799e+009 -1.71799e+009
这是一个奇怪的结果,对我来说没有意义。 有谁知道出了什么问题?我没有在网上找到任何东西。
Does anyone know what went wrong?
您尚未创建 GL context 并在使用 glGetDoublev()
和 glGetIntegerv()
之前将其设为当前:
In order for any OpenGL commands to work, a context must be current; all OpenGL commands affect the state of whichever context is current. The current context is a thread-local variable, so a single process can have several threads, each of which has its own current context. However, a single context cannot be current in multiple threads at the same time.
您可以使用 (Free)GLUT (among other things (not exhaustive)) 创建一个 window 和关联的 GL 上下文:
#include <GL/glut.h>
#include <iostream>
int main(int argc, char **argv)
{
// create context & make it current
glutInit( &argc, argv );
glutInitWindowSize( 200, 200 );
glutInitDisplayMode( GLUT_RGBA );
glutCreateWindow( "GLUT" );
GLdouble mvmatrix[16];
GLdouble projmatrix[16];
GLint viewport[4];
GLdouble winx;
GLdouble winy;
GLdouble winz;
glGetDoublev( GL_MODELVIEW_MATRIX, mvmatrix );
glGetDoublev( GL_PROJECTION_MATRIX, projmatrix );
glGetIntegerv( GL_VIEWPORT, viewport );
gluProject
(
0.0, 0.0, 0.0,
mvmatrix, projmatrix, viewport,
&winx, &winy, &winz
);
std::cout << winx << " " << winy << std::endl;
return 0;
}
输出:
100 100