3D requires RGB or Grayscale mode. It also requires a compatible GPU and for that to be enabled in Preferences > Performance. Were the 3D features available previously?
Agree with conroy. Check your document color mode. also verify the document size. On weaker graphics hardware, the 3D features may not work because they do not have the necessary resources to use large layers as textures.
Can you provide more system details, as well?
Ps CS5.1 has a software fallback for some of the 3D features, so not all 3D menu items are greyed out with a disabled GPU.
Thank you very much for responses!
Yeah! Reason of my problem was CMYK color mode. I set RGB and it is working! But my graphics card is really weak, and after some time, but only sometimes, i get attention message, and work become slow.
And there is more question....
So difficult to explain it...
I need to make ONE 3d object with a few ojbects with different settings of a material. It will be rough board with glassy sticker. I want to choose scene or camera setting for both material.I noticed that layers (bump, diffuse...) in 3d object is simple SmartObjects, and at any time i can to change pictures(maps). But it would be not bad, if i could to add some layers. Can i do that? Or other way?I hope it clearly.