Hey, from checking the code it looks like HDR makes a difference because when HDR is not enabled the image processing is done in a post process after everything is rendered costing another render pass. When HDR is enabled, image processing is performed during rendering of materials (to avoid the final renderpass) and typically an HDR background material will be used for the skybox making everything work however when you don’t have a skybox the clear color will be applied directly which is drawn when gl.clear() is called and no shader code is run where image processing could be applied to it. I think it is recommended to change the scene.clearColor yourself or use a skybox for this case.
@sebavan double check that i’m correct or if you think a code change should be done for this