private void bindFrameBuffer(FrameBuffer fb) {
        if (fb == null) {
            if (context.boundFBO != defaultFBO) {
                glfbo.glBindFramebufferEXT(GLFbo.GL_FRAMEBUFFER_EXT, defaultFBO);
                statistics.onFrameBufferUse(null, true);
                context.boundFBO = defaultFBO;
                context.boundFB = null;
            }
        } else {
            assert fb.getId() != -1 && fb.getId() != 0;
            if (context.boundFBO != fb.getId()) {
                glfbo.glBindFramebufferEXT(GLFbo.GL_FRAMEBUFFER_EXT, fb.getId());
                context.boundFBO = fb.getId();
                context.boundFB = fb;
                statistics.onFrameBufferUse(fb, true);
            } else {
                statistics.onFrameBufferUse(fb, false);
            }
        }
    }
Copy the source buffer to the destination buffer, including both color
and depth.

@param src the source buffer (unaffected)
@param dst the destination buffer
jme3-core/src/main/java/com/jme3/renderer/opengl/GLRenderer.java