WebGL: Prevent color buffer from being cleared

Question

Even if I remove

gl.clearColor(c[0],c[1],c[2],1.0);
gl.clear(gl.COLOR_BUFFER_BIT );

the screen still gets cleared at the beginning of the next draw cycle. Is there a way to prevent this. I´d like to achive some kind of overpaint effect.

Answer 1

When you create your WebGLRenderingContext you can tell it to preserve the drawing buffer.

gl = someCanvas.getContext("webgl", { preserveDrawingBuffer: true });

The default is preserveDrawingBuffer: false because it's faster in some cases.