Stop rasterizing the gradient on an object when expanding its appearance
When you expand the appearance of an object with a gradient, the gradient is rasterized, which I believe, defeats the purpose of using it considering the results. The resulting image has a lot of erroneous White specs. If there is a stroke aligned to the center, it creates two layers with the same gradient, which means you have to unite them with pathfinder. A layer that's shaped the same as the rasterized object with the gradient is the color gray.
The workaround is to apply a solid color, then expand, then reapply the gradient, but it took me some time to realize that would solve the problem. It would be better for Illustrator to be more direct and simply not rasterize the gradient when expanding appearance.
What can be done, I suppose, is converting these former gradient fills to freeform gradient ones (triangular mesh inside), but this would require some fat math and doubtedly a thing you want.
A mode where a gradient would be kept live but thus displayed wrong on a rotated surface (because it is, even if you use 'Off-Axis Front' that looks quite similar, because it feels like rotating along one axis only)... well, maybe. But the 3D in Ai is terribly dated and will not be fixed until is completely rewritten, which I suppose is in the development, according to some public hints from the management. Let’s hope that it will not worse.
I know its normal behavior, but it isn't practical to do a workaround.
Well, it the different story. This is not a bug. It is a completely normal behaviour.
Gradient in 3D gets distorted along two axes and thus can’t stay as a linear live gradient after you expand it.
That is why it warns you about it. So you do everything correct to workaround it.
Gradients are rasterized when you expand the 3D effect. It says it on the dialog for the 3D effect and the dialog when you expand the object.
What type of gradient are you talking about exactly?
This is not how it works for me.
Can you please provide steps and a test file or a video that demonstrates it?