roof by mass not shown on sections continously?

[jianlin.sunXCKBF]

Hi I have a weird situation where I created a simple 50mm roof based on a mass on a topography. When I cut a section through the roof, it would only appear in the section at certain position of my section cut. No overrides on VG and everything is turned on. The weird part is that if I move the section cut by arrow keys it will show at certain locations but not others. However my section cut is certainly through the roof and I'm sure the movements by the arrow key is not changing the circumstances of where the section is cut. I hope the pictures below explains the situation. Is anyone experiencing the same situation?

[jianlin.sunXCKBF]

Just want to add my process here:

1. Create topography
2. split surface
3. isolate split surface in 3D
4. export to DWG
5. create in-place-mass
6. import same dwg file, finish creating mass. Now this mass is based on the DWG file which has the contour information on the topography
7. create roof by mass by selecting all the triangles in the mass. (additional question here: why can't i create a floor based on the mass?)
8. set roof to be "picked face location: face at the bottom of the roof"
9. cut a section through the roof
10. problem appears

If anyone has seen the same problem, please let me know maybe we can figure it out together. Thanks!

[Anonymous]

I know this doesn't directly answer your question but it seems like a fairly complicated workflow? why would you not just use one floor with Modified Elements instead of your mass roof? This might solve your visibility issues as instead of cutting through multiple roofs by mass it would be cutting one floor. 

[jianlin.sunXCKBF]

Because my contour next to the entry of the building is not linearly sloped so that sub-elements can be adjusted easily. I can sort of fudge the sub-element heights but I found it taking much more time than the workflow above. If I carry the steps above it really is not that hard for making site elements such as roads follow the surface levels of any topography easily. The only reason why I do this is because topography does not support surface patterns. In order for me to show roads, for example, even if only just a graphical presentation (not needing to show pavement thickness etc), I have to either use the site-designer addon, which is very difficult to use at least for me, or use the above method.