Underlays - Odd Behaviour

[saeborne]

Hi all,

I'm having a strange issue with the display of underlays.

Let's say I have a 10 story project, and I'm in a 5th floor plan view. Under visibility properties, I set the underlay to be the 4th floor. All of the 4th floor furniture is visible, in a half tone. This is exactly how I expect it to look.

In that same floor plan, if I change the underlay setting to the 3rd floor, now my Level 5 slab object obscures the underlay. The underlay is only visible inside of shafts / slab openings.

I've tried in several other views also... Anytime the underlay is immediately below, everything looks fine. Any other level, then the slab obscures the underlay.

Any one have an idea as to what's going on?

Thanks,

Bryan

[sfaust]

underlays have always been a little goofy to me and I don't really think I understand how they are working, so I don't use them much. I would be interested if anyone has a good explanation of what it does...

[saeborne]

Here's a sample file that illustrates the problem. It's basically a blank revit file with some walls and floors. The walls spell out which level they are on.

Notice in the view "Level 4 - W/ lvl 3 underlay," I can see all of the 3rd floor walls.

However in "Level 4 - W/ lvl 2 underlay" or "Level 4 - W/ lvl 1 underlay" the underlay is obscured by the floor slab.

Strange, isn't it?

[twiceroadsfool]

Its not weird... Its the underlays range interacting with the view range of Level 4's Floor plan.

An underlay will exclude anything redundant that is in both the underlays *range* and the VIEW range of the view in question.

For instance: Level 4 with leve 3 underlay. The level 4 slab is in both, so its exluded from the underlay. Conversely, you see the level 3 furniture.

Level 4 with level 2 underlay: The slab youre SEEING is slab 4. But thats not whats hiding your furniture. whats hiding it, is the level THREE slab, which is visible in the range of the underlay (level 2- level 3). Hide the Level 4 slab, youll see the level 3 slab underneath it.

Make sense?

[saeborne]

Hi Aaron,

I suppose I understand in theory, but it doesn't behave as expected in practice. If what you're saying is true, then I should be able to modify the display of the underlay, but adjusting the depth of the view.

I've attached a new model that has two new views in it... They start with the name "Depth Clip."

By adjusting the view range in Level 4 plan views, I can't make Level 3 be obscured by the floor slab. Conversely, I can't make Level 2 NOT obscured.

Any thoughts on the matter?

[twiceroadsfool]

No, because underlays are based on LEVELS, not Views. Thats why i said *underlay range* and not *underlay view range*.

An Underlays range is from Its Level to the level above it... And you cannot adjust it. So if the view range of the view in question contains any elements that are also between the "Underlay level and the level above it", they are excluded.

If you want to test my theory, go in to your test file. In elevation, put an extra level between level 2 and level 3, midway up the flr height.

Then go to Level 4 with level 2 underlayed... Itll work perfectly.