问题
I am new to OpenGL and I am still experimenting with basic shapes. I sometimes find many functions like glEnd and many more, that are not mentioned in the OpenGL 3+ documentation. Were they replaced by other functions? Or do I have to write them manually?
Is there a tutorial online that uses OpenGL 3+?
As for " gluPerspective" I have read that it isn't used in Opengl 3+. Isn't it supposed to be a separate function in GLUT? what does it has to do with OpenGL 3+? Last, what does Transform( Width, Height ); do? (I found it in some sample code I downloaded, and I can't find it in GLUT or OpenGL).
here is the code:
GLvoid Transform(GLfloat Width, GLfloat Height)
{
glViewport(00, 00, Width, Height); /* Set the viewport */
glMatrixMode(GL_PROJECTION); /* Select the projection matrix */
glLoadIdentity(); /* Reset The Projection Matrix */
gluPerspective(20.0,Width/Height,0.1,100.0); /* Calculate The Aspect Ratio Of The Window */
glMatrixMode(GL_MODELVIEW); /* Switch back to the modelview matrix */
}
/* A general OpenGL initialization function. Sets all of the initial parameters. */
GLvoid InitGL(GLfloat Width, GLfloat Height)
{
glClearColor(0.0, 0.0, 0.0, 0.0); /* This Will Clear The Background Color To Black */
glLineWidth(2.0); /* Add line width, ditto */
Transform( Width, Height ); /* Perform the transformation */
}
/* The function called when our window is resized */
GLvoid ReSizeGLScene(GLint Width, GLint Height)
{
if (Height==0) Height=1; /* Sanity checks */
if (Width==0) Width=1;
Transform( Width, Height ); /* Perform the transformation */
}
回答1:
I sometimes find many functions like glEnd and many more, that are not mentioned in the OpenGL 3+ documentation. Were they replaced by other functions?
They have been completely removed, since their workings doesn't reflect well with how modern graphics systems work on both the hardware and the software side. glBegin(…) and glEnd() form the surroundings of the so called immediate mode: Every call causes an operation. This reflects how early graphics systems were built, some 20 years ago.
Today one prepares batches of data, transfers them to GPU memory and triggers batch drawings with a single drawing call. OpenGL does this through vertex arrays and vertex buffer objects (VBOs). Vertex arrays have been around since OpenGL-1.1 (1996), and the VBO API is founded on vertex arrays, so for any reasonable program VBO support was added easily.
Or do I have to write them manually? Is there a tutorial online that uses OpenGL 3+?
It depends on the function in question. For example the whole texture environment, combiners have been removed. Just like the matrix manipulation functions and the whole lighting interface.
What they did and configured is now done through shaders and uniforms. Since you're expected to supply shaders one might say, you're expected to implement this yourself. OTOH you'll quickly find out, that often writing a shader is easier and more concise, than fiddling with large numbers of OpenGL parameter setting calls. Also once you've progressed far enough you'll hardly miss the matrix manipulation functions. Every serious application dealing with 3D graphics maintains the transformation matrices itself; be it for enhanced flexibilty or simply because those matrices are required in other places, too, e.g. some physics simulation.
As for " gluPerspective" I have read that it isn't used in Opengl 3+. Isn't it supposed to be a separate function in GLUT? what does it has to do with OpenGL 3+? Last, what does Transform( Width, Height ); do? (I found it in some sample code I downloaded, and I can't find it in GLUT or OpenGL).
gluPerspective is part of GLU. GLU is a companion library of OpenGL Utility functions, that used to ship with OpenGL-1.1. However it is not part of the OpenGL specification and completely optional.
GLUT is something else again. It's a simplicistic framework for quick and dirty setup of a OpenGL window and context, offering some minimalistic input API. Also it's no longer actively maintained. Personally I recommend not using it. If you must use a GLUT API, use FreeGLUT. Or better yet, don't GLUT at all, use a toolkit like Qt, GTK or a framework like GLFW or SDL.
回答2:
Were they replaced by other functions?
No.
Or do I have to write them manually?
For old-style immediate-mode geometry submission you'll have to make your own work-alike. The matrix stack has a replacement.
Is there a tutorial online that uses OpenGL 3+?
At least one.
来源：https://stackoverflow.com/questions/7960398/opengl-deprecated-functions-and-gluperspective-and-transform