Updatenormals should do the trick too, but you're right, CountTriangles(surf)-1, tho it seems to work anyway.
Render times heavily depend on the situation, since this will generate more surfaces, you need to use it in the right way. eg. maybe you should lower the number of clusters, even 3*3*3 may be useful.
And this thing may also be a basement for an automated VIS system. you could precalculate the visibility of all clusters from inside every cluster. Using the old ICU Method of recognizing unique colors and Terabits speed boster could make it a real useful thing.
Render times heavily depend on the situation, since this will generate more surfaces, you need to use it in the right way. eg. maybe you should lower the number of clusters, even 3*3*3 may be useful.
And this thing may also be a basement for an automated VIS system. you could precalculate the visibility of all clusters from inside every cluster. Using the old ICU Method of recognizing unique colors and Terabits speed boster could make it a real useful thing.