你如何在OpenGL中获得模型视图和投影矩阵？

GLfloat modelViewMatrix[16];
glGetFloatv(GL_MODELVIEW_MATRIX, modelViewMatrix);

GLfloat projectionMatrix[16];
glGetFloatv(GL_PROJECTION_MATRIX, projectionMatrix);

GLfloat modelViewProjectionMatrix[16];
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glMultMatrixf(modelViewMatrix);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glMultMatrixf(projectionMatrix);
glGetFloatv(GL_PROJECTION_MATRIX, modelViewProjectionMatrix);

uniform mat4 modelViewMatrix;
uniform mat4 projectionMatrix;
uniform mat4 modelViewProjectionMatrix;