Tag Archives: Accuracy

BIM Element Wants and Needs

In recent project audits and reviews I noticed a few projects that had disconnected and un-parametric elements and objects to represent very simple model elements. A toilet, for example, with a separate drafted floor plan and 3d/elevation view.

It was explained that this was done to show the manufacturers specific dimensions, shape and style in plan. Although there are ways change or override an objects plan symbol to show exactly what is perceived as necessary, this raises a much bigger question. What really is necessary in a drawing/model element? We may want a plan symbol or elevation of an element to match identically to a manufacturers drawing, but is that really necessary? I would say an exact graphic representation to a manufacturers spec is very low on the priority list for a BIM element, at least in most cases.

The Needs

So what are the priorities for a BIM element? We can assign a hierarchy of what a BIM element should represent to better understand.

  1. A BIM element needs to be parametric with a single element representing all views. Without this criteria being met before all else, the drawings are prone to redundancies and inconsistencies, and we loose almost all efficiencies of a BIM model and BIM process.
  2. A BIM element should match the overall size of the manufacturers specifications. This ensures that critical clearances and space requirements of a specific model element are met. This is overall dimensions; because a basic 3D cube with an associated plan symbol may meet criteria #1 and would be far superior to disconnected 2d plan and elevation views of an element.
  3. A BIM element should be placed in the correct location as its overall dimensions relate to the space it will be installed/built in. It should be in the correct location in plan, elevation and 3d views to show its relationship to all other model elements.

After these criteria are met, an element will be consistent in all views, it will be easily managed, maintained and edited, it will represent the correct size and represent the design intent. Anything else a model element requires is not a project need, but simply a “want” of the designer.

What does this all mean? Simply that in most cases we do not need a manufacturers specific element. Rather we need a generic element that represents the manufacturers size and the designed location of an element.

The toilet, as in the initial example, could be a basic out of the box ARCHICAD toilet that was set to the manufacturers size and placed correctly in plan. This would be enough to convey the design intent and document the building sufficiently.

The Wants

There may be some obvious additions to the hierarchy above, but rarely if ever should these take priority over the needs of a BIM element.

  1. Elements that are not part of the documentation, such as furniture or decoration used for visualization only may not require much thought towards what the plan or elevation views look like, but only need to show a quality 3d view. Elements that are placed only for BIMx or renderings would be a waste of time to build a correct plan symbol and parameters for listing into the element.
  2. Elements that require a manufacturers specific appearance to properly leverage a models visualization to make selections. Appliances and plumbing fixtures may meet this exception, but these elements should also be modeled so that their plan symbol, elevation view and 3d representation may meet the BIM element criteria above.
  3. An element that needs a higher level of accuracy to show relationships to finishes may require additional criteria, but may not ignore the top 3 criteria listed above. For example, a wall mounted faucet may need to show relationship to grout joints. So an additional element criteria would be manufacturers detailed dimensions. For this type of element all other criteria must be met; which means a custom object would need to be built or downloaded to maintain the integrity of the model.

Thinking Outside the Box

A few weeks ago I gave an example from Rina & Maggie’s project using a fence object, complex profile, or morph object in place of multiple column elements.

Here is another example of that creative thinking. Using that same fence object Matthew placed dentils on his crown, making light work of what would have otherwise been incredibly tedious to place individual dentils. Of additional benefit, the spacing and “slat” dimensions are set right in the object, so spacing and sizing changes can be made and overall spans can be adjusted globally or per section of crown.

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Granted, we don’t do a lot of trim packages involving dentils, but this is the sort of out of the box thinking that can gain massive amounts of efficiency for any design. Using the right tool for the job is crucial to maximize efficiency, precision and flexibility.

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Simplifying Site Mesh

Some site surveys we get are very detailed, showing contours every foot even for very steep sections of the site. Some of these sites also have a high number of nodes associated with the original DWG file from the surveyor. In the image below, the bold gray line towards the bottom of the survey is actually the same line type/pen as the rest of the contours, but it is selected and all nodes show as gray. The nodes are so close that the line appears as a bold gray line.

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The result of this highly detailed site survey is a very high polygon count for the site model. An easy way to simplify this is to do a little editing before applying the contours. In illustrator you can open the original DWG and select simplify. If “Straight Lines” and “Show Original” are checked you will get a preview of the reduction in nodes/segments that will result from the operation. Adjust the Angle Threshold until you get a simpler but still accurate site survey.

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Next export the drawing from Illustrator back to DWG and place into the ArchiCAD worksheet as normal. A little additional drafting may be required (as is normal for any survey) to consolidate linework & make all polylines continuous. The result is a much simpler topo drawing that can be used for creating site models and for drafting 2d site plan elements.

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Notice the above image has much simpler contour lines. This image also excludes all property & setback lines. These should always be pulled from the original survey and reapplied to the revised topography to ensure all surveyed property line elements are at the original precision.


If you have worked with ArchiCAD door and window schedules for more than about 30 minutes you have faced the occasional stubborn door or window that either will not show up on the schedule at all, or will not populate the room name or home story column of the schedule.

Window/Door Will Not Schedule

There are a few trouble shooting items to review to help resolve this problem. If the object will not schedule at all, the simple solution is to verify that it is not being excluded from by the schedule criteria list. Some of these lists can get to be very complicated, in order to allow the use of the window tool to represent many different (non-window) elements, such as cased openings, fireplace components, wall niches, etc.

Take a quick look at the Schedule Scheme Settings in the upper right corner of the schedule window:

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Then review the Schedule Criteria List in the scheme setting dialog box. These settings should be as minimal as needed to exclude what shouldn’t show up, but leave what should. Here is a great example of a list that works for a very complicated 4 story remodel project:

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If this is not the cause of the problem check your schedules view settings in the view map. Verify the layer combination is not excluding the walls that contain the door or windows. Also, verify the renovation status is not excluding the walls OR door/window units that the elements are defined as.

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Room Name or Home Story Will Not Schedule

This can be a trickier one to track down, since there are several reasons this happens. The first step I recommend is to review the window or door in plan view to assess its relationship with the schedule it should be scheduling to. There is a great shortcut for opening a selected schedule item in plan (or 3d) views.

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Once you have the opening selected in plan view select the zone it should be related to.

Screen Shot 2014-12-08 at 2.01.30 PMEverything looks ok and W01 should schedule… But it doesn’t! So look closer and you may find the zone is not running to the face of finish. Walls may have moved or the zone may have not been updated if linked to a zone boundary.

Screen Shot 2014-12-08 at 2.01.40 PMIf this all checks out and the window still will not list a room name check the window or door orientation. Remember that doors and windows have an outside and an inside, even if the whole element is technically not part of the building envelope. When you place a window or door you define the exterior via the little “sun” icon designating the prescribed exterior face of the wall.

Screen Shot 2014-12-08 at 2.08.48 PMIt may not be extremely clear which side is designated as exterior AFTER the unit is placed. But you can try “flipping” the orientation in the window/door selection settings. This redefines the exterior as opposite the installed orientation. It also flips the doors orientation in the wall; but a simple rotate and click will put the unit in the correct orientation while maintaining the newly assigned “exterior” face.

Screen Shot 2014-12-08 at 2.08.57 PMIf THIS doesn’t work we will need to dig deeper. Doors and windows do not associate to a distance greater than about 42″ above or below their story extents, as measured from their insertion point. The insertion point is the Header or Sill to _______ definition. If you insert using a typical header to home story setting, the insertion point is the header. If that header point is below its home story, regardless of the location and association of the zone to that story there is no practical method of listing a room name.

The solution to this is to set up stories appropriately. Half stories should have their own designated stories; this is an easier solution earlier in the project so discuss with the DDC & your model manager as soon as possible. We can show walls on multiple stories and have near perfect graphic control of what is shown as cut through using the floor plan cut plane settings. But that is a story for another post…


Recently I have received several questions regarding the uses of the Hotspot tool. Fortunately we have several projects and AC users that exemplify the use of hotspots to streamline documentation.

Chris W. has developed a system of hotspots for interior elevations to create consistent drawing margins and to easily place on layouts with the proper and consistent drawing extents. His process is to place hotspots with consistent margins from the inside face of finish of the interior elevation (from ridge for vaulted rooms). See image 1.1.


Next the zooming in the view settings (view map) should be set to “Fit in window“. See image 1.2. This ensures that both the view when opened from the view map and the drawing when placed to the layout snap to the farthest extents of drawing content; which should be the hotspots from image 1.1.


The last step is to simply place on sheets; via the organizer, drag and drop or right click on the layout and select “Place Drawing“. See image 1.3.


For the pacific project we have a Cadimage covering to show a barrel tile roof. The covering object has a snap point that is not related to the actual ridge of the project. In order to ensure the dimension is showing precisely and in relation to the actual ridge a hotspot was placed. See images 2.1 & 2.2.



Another example of the use of hotspots is to set consistent floor plan drawing extents for multiple storied buildings or for multiple buildings laid out in one PLN file. See image 3.1 for an example of this.


Hotspots can also be useful in creating or editing 2d symbols or scripts of GDL objects. Lastly they are very useful when developing complex profiles. A hotspot added to a profile will show up as an alternate snap point at the ends of a profile applied to a beam or column.


Recently a question about beam and roof matching has come up. For example, if you place a roof at a 4.75:12 slope, your beam would need to be 21.5953º (and that is missing a few digits) to get close to matching. In the beam settings this would round to 21.60º by default, since we are only able to place beams to a two digit precision.

To match a beam precisely to the roof slope you will need a working section through the roof showing the full length of the roof and beam in an orthogonal elevation view.

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Start by aligning the top node of the bottom slope end of the beam with the appropriate skin or core line of the roof (this does not need to be an end node of the roof, but does need to be snapped to the roof skin separator line). Next select the top node of the top slope end of the beam and select the “modify angle” button on the pet pallet. Last move the top node to the same line as the bottom node previously aligned. Note that you will get a checkbox or solid pencil symbol next to the cursor when you are snapped to the line.

The beam settings will still show as rounding to the nearest two decimal places, but the beam will perfectly align with the roof slope no matter how close you zoom in. From here it is a simple eye-dropper and inject command to get the other beams elevations and slopes to match.

I would also like to mention one more time, this is another reason it is critical to give similar or identical items a common element ID to differentiate them from other elements. Using the find and select tool for all beams with an ID of “Typical Rafter” and a beam width of x” will allow you to quickly isolate the beams that need to be modified to match the one that now aligns with the roof.