Visual Particle System in an OpenGlWidget

Development
5

You can’t put OpenGL calls in draw(). To see why, look at this simplified version of the draw routine in Window::run().

nvgBeginFrame(vg, fbWidth, fbHeight, pixelRatio);

APP->scene->draw();

glViewport(0, 0, fbWidth, fbHeight);
glClearColor(0.0, 0.0, 0.0, 1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
nvgEndFrame(vg);

NanoVG functions don’t do any drawing. They add commands to a command buffer which is converted into OpenGL calls when nvgEndFrame() is called. If you draw anything directly in draw(), it will be cleared with glClear(), and then your NanoVG stuff will be drawn over the cleared screen in nvgEndFrame().

I suggest looking at the documentation of OpenGlWidget. The only example of OpenGlWidget I’m aware of is OpenGlWidget itself, which draws a colorful triangle in its drawFramebuffer(). You should not attempt to call NanoVG functions in this method unless you understand exactly how NanoVG is implemented.

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