Hi Zhenfeng,

Thanks for posting on the forums!

I attempted to replicate the error message you're seeing, but I'm afraid that I wasn't able to make it appear, even for extreme surface definitions. Where specifically are you seeing this message? Is if after modifying the polynomial surface itself? Does it appear if you attempt to perform some optimization? If it's during optimization, does this message occur at the beginning of optimization, or does it pop up part-way through?

Without being able to see your file, my first thoughts are that the added field points might have extended the semi-diameter of that surface such that it is attempting to define a sag which rays cannot intersect with. The workaround for this case would be to try and create a less-extreme sag definition so that rays can hit the polynomial surface, and optimization can be performed from there.

Of course, I think we could provide more insight if we were able to see file first-hand. Is that something you can share here? You can create an archive file (.ZAR extension) by navigating to the File tab...Create Archive -- this will allow us to fully reproduce your system. If you'd prefer, you can also create a case with us directly so that you can keep your file private.

Let us know how these thoughts work out for you!

~ Angel

In general, when designing with aspheres, always define enough field points that the aspheric surface is fully illuminated by rays from at least one field point over its whole aperture. If you don't, you can get 'dark regions' where no light hits and the asphericity produces an untraceable surface.

Always remember that spherical surfaces are defined across their whole aperture by a single variable, radius of curvature, so you can be sparing in the use of field points. Once you start using aspheres, always *start* with enough field points to illuminate the whole surface. More is better with aspheres.

HTH

- Mark