Platform-Specific Notes on OpenGL Implementations

Caveats

1. Unless stated otherwise, all of the notes below are true as of late summer 2014. Development environments are constantly being extended and updated, hence some of these may be fixed or corrected over time.

The Notes

• Macintosh (< 10.9)
  1. Rendering contexts (RCs) beyond 2.1 are not available on pre-Mavericks Macintosh OS versions. While some of the VAO, VBO, and shader-based facilities used on the pages of this site are available (sometimes as extensions) in 2.1 RCs, many are not. Attempts to develop shader-based OpenGL on Macintosh OS versions less than 10.9 are highly discouraged.
• Macintosh (≥ 10.9)

  A problem unique to AMD systems is that disabling a vertex attribute array and setting its value instead using glVertexAttrib* does not work if the vertex attribute is in location 0. You will see several demo programs on this web site that force the mcPosition variable into location 0 since that attribute will always have a VBO in our examples. This problem is known and will be fixed at some point, but the last time I checked, it had not yet been corrected.

  Additional caveat: It is possible that some of the following issues are only present on AMD systems. I have not verified whether these issues are present or absent on Macintosh systems with NVIDIA GPUs.

  1. The freeglut window system interface does not enable use of RCs beyond 2.1, even on OS version 10.9. Use of the GLFW window system interface is highly recommended.
  2. You can safely ignore the two warning messages that appear when compiling Controller.c++.
  3. The glDrawElements function can only be used along with an element buffer. Hence the fourth parameter to glDrawElements must either be 0 or an integer offset into the element buffer. In particular, it cannot be a local integer index array. If you pass such a local array, your program will compile, but it will produce an "invalid operation" error at runtime, and the call will be ignored.
  4. Interface blocks can cause problems if some shader stages through which they are passed do not use all fields. The compiler (or linker) seems to incorrectly eliminate them. That then causes problems at link time. Typically the program will just segfault!
• Dynamically loaded libraries on Macintosh systems: Before trying to run your program in a given Terminal window on the Macintosh, enter the command: export DYLD_LIBRARY_PATH=../lib This command need only be entered once per Terminal window. Alternatively, you can just include it in your shell startup script (i.e., .bash_profile, .bashrc, or whatever yours is called), then it will be set automatically for every Terminal window.