highpoly model as lowpoly & subdivision count

Hey there

I have a 21M tri model in painter, it's suprisly going well until i try to give a displacement to the mesh with height channel.

Question: Can i turn OFF tesselation completely and just displace the vertexes with the height channel?

If i can't turn off tesselation, then subdivision count means "tri of my mesh x 4"?

Because then that's an u'lala but no go baby situation! 😛

Thank You for your answer in advance!