gles2

gles2

Example how to do GLES2 rendering regardless of which OpenGL driver is loaded. It will set up EGL context either with Broadcom or with vc4/mesa driver.

Requirements

Check the readme files for gles2_bcm and gles2_drm demos in parent folder for setting up required libraries and development header files.

Compiling & running

Execute make to build.

You can execute make run to build & upload & run executable on Raspberry Pi. By default it will try to connect to [email protected] host. You can override it by setting PI variable: make run [email protected]

You should see colorful triangle spinning. By default vsync is enabled, but you can disable it by changing last argument to context_set_vsync function.

Using in your code

In case you are inegrating this code into your application, these are "public" functions that you should use:

void api_load(void);
void api_unload(void);

void context_init(struct context* ctx);
void context_done(struct context* ctx);

void context_present(struct context* ctx);
void context_set_vsync(struct context* ctx, int vsync);
void* context_get_address(const char* name);

Other functions are implementation details, do not call them directly.

Start with calling api_load function. It will load all necessary dynamically libraries. You need to do this only once. If you want clean shutdown, then at end of program call api_unload to unload dynamic libraries. Rest of context_* functions can be called only after api_load was called and before api_unload will be called.

Now for each OpenGL context you want to create call context_init function. Then use context_get_address function to load GLES2 functions. Do not link to system libGLESv2.so library, because depending on which backend is used, the GLES2 library can be different file. Use context_present to swap back buffer to screen. VSync can be controlled with context_set_vsync function, use 0 to disable and 1 to enable vsync. To cleanly release OpenGL context, call context_done function.

You probably will want to edit code a bit to handle errors more gracefully. Currently all error conditions are handled with assert.