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Thursday, March 31, 2011

Revit & Inconsistent Units

Probably THE error box in Revit that have caused me the most grief, over the years I´ve spent hours and hours on trying to work around it. But once I got the hang of it, and not least once I understood WHY Revit would throw that error box at me, it´s not that bad. Hope some of you will find this helpful.

Let´s begin with some basic algebra:

<100 mm * 100 mm = 10,000 mm²>

So if you have a Length parameter, and try to use a (Length * Length) formula, you´ll get the " Inconsistent Units" error, because (Length * Length = Length Squared). Only way around is to neutralize the units on at least one of the parameters in the formula. The easiest way to neutralize a unit is by dividing by 1 (one):

<100 mm * (100 mm / 1 mm) = 10,000 mm>

Why? Because <100 mm / 1 mm = 100> (unit less) and <100 mm * 100 = 10,000 mm>

And another example:

<100 mm * 100 mm * 100 mm = 1,000,000 mm³>

So again, if you need to multiply 3 length units in a Area or Length parameter, you´ll need to neutralize the units as above.

<100 mm * 100 mm * (100 mm / 1) = 1,000,000 mm²>
<100 mm * (100 mm / 1) * (100 mm / 1) = 1,000,000 mm>

So far, dividing by 1 (one) have been a success, but in some cases it´s necessary to multiply by 1 (one) instead. An example: You want to multiply two Number parameters into a Length parameter:

<100.0 * (100.0 * 1) = 10,000 mm>

Another common situation for the "Inconsistent Units" error, is when quantifying costs in schedules

In the schedule you already have "Area" and "Cost" but want to add a Calculated Value "Total Cost":

<Area * Cost = Inconsistent Units>

<(Area / 1) * Cost = Total Cost>

There´s probably a gazillion other possibilities, but I hope that this explains why we are getting the Inconsistent Units Error, and how to work around it.

Wednesday, March 30, 2011

Win a Free Pass to AU 2011 in Las Vegas

Take a moment to complete this short survey by April 5, 2011, and be entered in a drawing to win a free AU 2011 3-Day All-Inclusive Pass.

Autodesk University 2011 Call for Proposals

Copy/Paste from AU Online:

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Submission Deadline: May 6, 2011

Wednesday, March 23, 2011

Revit 2012 - Round Function In Formulas

There has been lots of blogging about the new features in Revit 2012 over the last couple of days, but to my surprise I´ve not seen the the new rounding functions mentioned yet.
OK, it may be a minor feature to most, but I use formulas a LOT, and find these new functions pretty sweet.

I also posted this, and lots of other formulas to use in Revit, in this thread at the Revit Forum.

Values in formulas can be now rounded up or down. For example, when riser height is calculated, one needs the function “round” to find the appropriate value.
The round function returns a number rounded nearest to a whole number. It doesn’t take into consideration rounding direction (round up or down). If the number is (for example) from 24.5 to 24.9, the function rounds it to 25. If it is from 23.1 to 23.4, the function rounds it to 23.
round ( 23.4) = 23
Round ( 23.5) = 24
Round ( 23.6) = 24
Round (-23.4) = -23
Round (-23.5) = -23
Round (-23.6) = -24
The syntax for the round function is: round( number)
number is the number to round.
“x” is a unitless value that should return the largest integral value less than or equal to x.
For example:
roundup ( 23.0) = 23
roundup ( 23.5) = 23
roundup ( 23.9) = 23
roundup (-23.0) = -23
roundup (-23.5) = -24
roundup (-23.9) = -24
The syntax for the roundup function is: roundup (number)
number is the number to round up.
“x” is a unitless value that should return the smallest integral value greater than or equal to x.
For example:
rounddown ( 23.0) = 23
rounddown ( 23.5) = 24
rounddown ( 23.9) = 24
rounddown (-23.0) = -23
rounddown (-23.5) = -23
rounddown (-23.9) = -23
The syntax for the rounddown function is: rounddown (number)
number is the number to round down.
Note that when numbers such as 23.5 are rounded, they can result in either 23 or 24. To produce a stable result, for all the .5 cases, we round to the larger integer. That means that 23.5 is rounded to 24, while -23.5 to -23

Monday, March 14, 2011

Creating pleasant batters in Revit topography.

Preamble.... Ever tried to make the land around your building pad flow gently down to harmoniously meet the correct level only to find jagged surfaces and 'zigzagging'. Well now your woes are over.

1. In a plan view, mark out the area you wish to be flat (or evenly sloped with a minor tweak to the method) with model lines, ensure that they are a continuous chain for speed sake.

2. Use the 'split surface' tool and 'tab highlight chain' with the 'pick' tool and click to select the pad outline and 'finish' to split off the pad.

3. Use the 'split surface' tool on the remaining (outside the pad) surface and 'tab highlight chain' with the 'pick' tool with an offset of your desired batter distance (if it is steep terrain and you require a minimum grade you may want to manually draw these lines) and click to select the pad outline and finish to split off the batter.

You should now have 3 different surfaces, the building platform, the batter and the remainder...

4. Edit the building pad portion of your surface and delete any internal points then finish. Do the same with the batter portion being diligent to not delete ANY of the edge points.

I have tried for a few years placing points manually (0mm relative to surface) to make this work with mixed results. If you use the split surface tool, points are generated along the split lines based on the triangulation edges that define the surface and generate contours

5. Use the 'merge surfaces' tool to join the building pad and the batter sections of topography together. Ensure that the 'remove points on common edges' is unchecked.

6. Edit the newly joined toposurface. You will find a trail of points along the line of the recent join. select all these points and change their height to the desired level. If you require a slope to your pad, switch to the predefined elevation/section and 'rotate' the points to your desired slope, before losing selection. Finish the surface.

7. Use 'merge surfaces' to combine the two remaining surfaces, again ensure that the 'remove points on common edges' is unchecked.. The result is an accurate batter between the original topography and the desired pad.

If you create a building pad with the 'building pad' tool and cut sections, you will find that the surface is pretty damned accurate, almost indistinguishable in 3D

Thanks to Tim West, who wrote this tutorial on the Revitforum, and allowed us to repost it here.

Monday, March 7, 2011

Best post of the month - Febuary 2011

Kinda awkward to congratulate this months winner, since the winner was... well... me :p

It all started with a challenge to create an L shaped corner piece, and to control the angle of the "L" by a parameter, so that it could adjust to any angle between 5 and 355 degrees.
The challenge somehow got totally out of control, and ended up with a couple of us making fully parametric clocks ;)

You can read the entire thread, and download the .fra from here

I think this post was awarded, not for the parameters, but for the trick with using profiles to drive the Hands on the Clock.... Well, that, and maybe the digital display...

The runners-up this month were:

Second place:
Aaron Maller for his post in the Casework Thread, explaining when to use shared nested families, and when not to.

Third place:
Mark Balsom, for his post about Short Cut Key Magic