Underlay Behavior EXPLAINED

[mschroeder]

If you have ever wondered why some walls don't show up in underlays or show up inconsistently from floor to floor, or why roofs and view ranges affect their behavior, then read on.

First rule of underlays: Underlay view extent properties (cut, range, depth) are not user modifiable and not coupled to any other view's properties.

For "Plan orientation" underlays:
The cut plane of the underlay is always taken at the level above the selected underlay level and looks down to the selected underlay level.
If you try to underlay the highest level then the underlay cut plane is set infinitely above the top level.

"Reflected Ceiling Plan" orientation:
The cut plane of an underlay is set to the selected underlay level and looks up to the level above the selected underlays level.

It's also been mentioned "If objects are visible in the view range of your current view, AND in the view range of your Underlay, they are automatically hidden in your underlay, so there isnt a double instance."
I can find no evidence of this. Instead, the object's line style switches from an override state to normal object style when the object is within the view range.

I hope some of you find this useful.

[twiceroadsfool]

It's also been mentioned "If objects are visible in the view range of your current view, AND in the view range of your Underlay, they are automatically hidden in your underlay, so there isnt a double instance."
I can find no evidence of this. Instead, the object's line style switches from an override state to normal object style when the object is within the view range.

I hope some of you find this useful.

This occured on one of our roof plans, which prompted my searching for it. thats why i mentioned it yesterday.

We have a roof plan with a cut plane of 45' (first floor plan) and a bottom and view depth of 10' (first floor plan).

If you underlay the First Floor Plan, (cut plan of 4' (first floor plan), top of 8' (first floor plan) , the walls on the first floor plan will NOT show up for us.

They are taller than 10 feet, so they show up in both view ranges. The underlay will be missing all of those walls.

[mschroeder]

This occured on one of our roof plans, which prompted my searching for it. thats why i mentioned it yesterday.

We have a roof plan with a cut plane of 45' (first floor plan) and a bottom and view depth of 10' (first floor plan).

If you underlay the First Floor Plan, (cut plan of 4' (first floor plan), top of 8' (first floor plan) , the walls on the first floor plan will NOT show up for us.

They are taller than 10 feet, so they show up in both view ranges. The underlay will be missing all of those walls.

Can you post an example?

[twiceroadsfool]

See the attached. The three walls that are visible in the underlay are ONLY visible in the View range of the First floor plan (the underlay). The View range of the roof plan itself does not extend down that far, so it will display the information in the underlay.

The other three interior walls show up in BOTH view ranges. Becayse theyre already *visible* in the roof plan, they will not display in the underlay. If you edit the roof plans view range so it doesnt go down to intersect those walls (put it at 3' below the roof plan) then youll notice that they suddenly show up in the underlay, because they are now not *visible* in the roof plans view range.

Yesyes?

[mschroeder]

The other three interior walls show up in BOTH view ranges. Becayse theyre already *visible* in the roof plan, they will not display in the
underlay..
These walls are just obscured by your roof (temporary hide the roof and see what I mean)



If you edit the roof plans view range so it doesnt go down to intersect those walls (put it at 3' below the roof plan) then youll notice that they suddenly show up in the underlay, because they are now not *visible* in the roof plans view range.

Right, but let me reiterate "the object's line style switches from an override state to normal object style when the object is within the view range." Revit does not hide anything from you.

[twiceroadsfool]

These walls are just obscured by your roof (temporary hide the roof and see what I mean)



Right, but let me reiterate "the object's line style switches from an override state to normal object style when the object is within the view range." Revit does not hide anything from you.

Um, youre not getting what im saying...

If i wanted to see the walls by hiding the roof, i wouldnt be using an underlay at all. The whole point is to work on the roof WHILE looking at whats below. While it may change the line styles, it DOES remove those walls from the underlay.

If you hide the roof, you arent seeing walls in the underlay, youre seeing walls in the actual view. For instance:

In the attached file, the exact conditions i presented before are present, except there is now a floor at the third level. So temporarily hide the roof: The three walls that are *in both view ranges* STILL dont show up in the underlay, and now that the floor is in the way you cant see them.

[mschroeder]

Um, youre not getting what im saying...

We're going in circles. Believe me, I've had Autodesk clarify this through support requests, and even though this feature is working as programmed, they understand the confusion and have submitted it for enhancement.

No sense in beating a dead dog - I thought that a concise description (It's not covered well in Revit's help) of the underlay behavior would help some people understand why certain things don't show up, which is why I submitted it to the forum in the first place.

[twiceroadsfool]

Understandably so. Likewise, im trying to clarify for people who have the same mishap with their underlays, that items in their underlays WILL disappear depending on the view range of the view they are putting the underlay in, and the objects in the underlay themselves.

I too have had this clarified:

http://usa.autodesk.com/adsk/servlet/ps/item?siteID=123112&id=7150411&linkID=3770375

Quoted from Autodesk: Issue


When you tried to underlay a floor, only doors and windows were visible.


Solution


This issue occurs because there is an incorrect view range in the main view. If the view range intersects the geometry of a level in your main view, that level cannot be used as an underlay in the main view.

For example:

In the main floor level, the bottom of the primary range is set to main floor with an offset of -1’-0” and/or the View Depth has similar settings. The level below will not be an option for an underlay because it is already part of the primary view.

To correct this issue, you will need to reset these values to have no offset.

So for people who need view depths set extremely to achieve their goals (such as a roof plan that reachs down almost to the ground plane), then their underlays will have items removed, as i said in my first post.

[dbaldacchino]

For "Plan orientation" underlays:
The cut plane of the underlay is always taken at the level above the selected underlay level and looks down to the selected underlay level.

This doesn't seem to be the case and I'm still struggling to figure out what's the logic that Revit is using to display an underlay. See attached file. I have an underlay set to level 3. Per your explanation, the underlay cut plane should be at level 4 looking down on to level 3. So in theory, my underlay should look like Level 4 plan in the example (I set the cut plane here to have a 0 offset). But when I underlay Level 3 in Level 1, I get a roof plan view with nothing being cut. Why?

[amara]

I would expect an underlay be used to show overhead elements - beams, canopies, etc. Unfortunatly this is not the case. Beyond what's being mentioned I suppose there is a place for improvement where visibility control (both visibility of elements and individual view range control) be set for the underlay (underlayed ceiling plan for example) individually to show only certain elements and specifying linetypes for these elements. I wonder how others are dealing with the issue of overhead elements other than simply drafting lines.

[dbaldacchino]

Well I'm trying to understand Revit's thinking just for that reason....I want to turn certain underlays on and then use the linework tool to set certain edges to <overhead>. When the underlay is turned off, the linework stays. Now that brings another point....I wish we could specify whether this linework acts as detail lines or model lines, as right now I have to make these changes in ALL plan sheets separately, including the "working" plan views, in order to show overhead items. Sure, I can use model lines and lock them, but I don't like that workflow. I think the the underlay should let the user choose from existing views in the project, thus giving you totla control over HOW the unedrlay looks, and also being able to pick a color/opacity.

[amara]

Furthermore underlays don't print or export. So it seems they are meant to be only for editing purposes. The potential is much more.

[dbaldacchino]

Update:

I heard back from Support about the behavior of underlays.

"There is no cut plane corresponding to the underlay. What you specify is an underlay range and any element which overlaps that range is displayed in its entirety. Setting Level 3 as the underlay results in an underlay range extending from Level 3 to Level 4, which results in the display of the entire roof."

Check the example file I posted....this response is in relation to it. It makes sense now. For example, go to Level 1 and set the underlay to Level 2. The roof will show up in its entirety. That might be confusing, but if you go to an elevation view, you'll see that the roof starts between level 2 and 3, so Revit displays it all. Now give the roof an offset of 3' so it starts exactly on Level 3. Look at the underlay.....the roof doesn't show up anymore.

As to Phasing, the phase is controlled by the view you're in and the Phase Filter settings for the view. So if your view is set to New Construction, your Underlay will display as New Construction with the same Phase Filter settings applied to the view (colors and linetypes for the Underlay change too, but they show in halftone).

[FOUTJM]

for structural framing your underlay will not show if it is on coarse detail level as well. it will have to be on medium or fine.

[tedg]

for structural framing your underlay will not show if it is on coarse detail level as well. it will have to be on medium or fine.

Thanks for this little nugget!
It was the reason I searched for this topic.
I have framing plans (set to course view) where I wanted to show the framing below as an underlay, and for some reason joists show up but W-beams don't?
I suspect it has something to do with how joists are shown in the course view setting vs w-beams.

Now to see if I can force a work around, but this helped to understand the issue.