_GL

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Revision as of 06:07, 30 April 2022 by SMcNeill (talk | contribs) (Created page with "{{DISPLAYTITLE:_GL}} 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. {{PageSyntax}} :SUB _GL :: ''REM Your OpenGL code here : END SUB {{PageDescription}} * 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 '''Syn...")
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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.


Syntax

SUB _GL
REM Your OpenGL code here
END SUB

Description

  • 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.


Example

  
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  


See also



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