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58 lines
2.2 KiB
Markdown
58 lines
2.2 KiB
Markdown
# Using libprojectM in Emscripten
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projectM supports OpenGL ES rendering, and can be compiled into WebAssembly for use in browsers. WebGL is similar to
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OpenGL ES, but not identical, so a few additional considerations apply to get projectM running with Emscripten.
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## Additional Build Settings
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A few additional build settings will be required when building an Emscripten wrapper. Pass these flags/parameterrs to
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the Emscripten linker:
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- `-sUSE_SDL=2`: It is highly recommended to use Emscripten's built-in SDL2 port to set up the rendering context. This
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flag will link the appropriate library.
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- `-sMIN_WEBGL_VERSION=2 -sMAX_WEBGL_VERSION=2`: Forces the use of WebGL 2, which is required for OpenGL ES 3 emulation.
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- `-sFULL_ES2=1 -sFULL_ES3=1`: Enables full emulation support for both OpenGL ES 2.0 and 3.0 variants.
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- `-sALLOW_MEMORY_GROWTH=1`: Allows allocating additional memory if necessary. This may be required to load additional
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textures etc. in projectM.
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## Initializing Emscripten's OpenGL Context
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In addition to the above linker flags, some additional initialization steps must be performed to set up the OpenGL
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rendering context for projectM. Specifically, the `OES_texture_float` WenGL extension must be loaded explicitly to
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support the required texture format for the motion vector grid. The following code template can be used to set up a
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proper SDL2/WebGL context for projectM:
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```c
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#include <emscripten.h>
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#include <emscripten/html5_webgl.h>
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#include <GL/gl.h>
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#include <SDL.h>
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int main(void)
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{
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// Init SDL's video and audio subsystems
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SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO);
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// Create the SDL window (will be tied to the Emscripten HTML5 canvas)
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SDL_window* window = NULL;
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SDL_renderer* renderer = NULL;
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SDL_CreateWindowAndRenderer(1024, 768, SDL_WINDOW_OPENGL, &window, &renderer);
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if (window == NULL || renderer == NULL)
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{
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fprintf(stderr, "Failed to create SDL renderer: %s\n", SDL_GetError());
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return 1;
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}
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// Enable floating-point texture support for motion vector grid.
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auto webGlContext = emscripten_webgl_get_current_context();
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emscripten_webgl_enable_extension(webGlContext, "OES_texture_float");
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// Initialize projectM and put all other stuff below.
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return 0;
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}
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``` |