In order to use OpenGL drawing commands, you must do so from inside a SUB procedure called _GL, which enables the commands to be rendered.
- OpenGL commands are valid outside of SUB _GL, as long as the sub procedure exists in your code.
- Attempting to use OpenGL commands without having SUB _GL in a program will result in a Syntax error, even if the syntax is valid.
- SUB _GL cannot be invoked manually. The code inside it will be called automatically at approximately 60 frames per second.
- Using INPUT inside SUB _GL will crash your program.
- If your program needs to perform any operations before SUB _GL must be run, it is recommended to use a shared variable as a flag to allow SUB _GL's contents to be run. See example below.
DIM allowGL AS _BYTE 'perform startup routines like loading assets allowGL = -1 'sets allowGL to true so SUB _GL can run DO _LIMIT 1 'runs the main loop at 1 cycle per second 'notice how the main loop doesn't do anything, as SUB _GL will be running 'continuously. LOOP SUB _GL IF NOT allowGL THEN EXIT SUB 'used to bypass running the code below until ' startup routines are done in the main module 'OpenGL code starts here 'The code in this area will be run automatically at ~60fps END SUB
- [List of OpenGL commands] All commands in the list are valid. For those without a wiki page, usage follows OpenGL standards.