Background image problem!

What I though to be a HDRi problem in my previous post is in fact a problem of background image.

In fact I set my HDRi visible which seems to transfer it as background.

So, if we load a background image from the rendering wizard, the image appears during rendering but, I don't know why, layers wizard button is grayed and if we have to modify something about the background image, I have to direct use the layers wizard provided in sketchup.

And here is the problem because if we load or maybe just modify an image in this wizard, it's not displayed during rendering and more, it seems it's not taken in accound in reflexions.

As I said, it's possible to displayed it afterwards by calling FX dialog. Maybe other function I don't know but, the background is just displayed but have no effect on the rendering of course.

Another question: it seems an HDri, used as background is maaped flat and the Cylindrical/Spherical mapping button are grayed. That's a problem because HDri are often spherical so background is in that case distorded.

Alain