Sketching Tangent Lines

A post based on my responses at the Autodesk Forum: Tangent Circle to Tangent Circle.

It could be easier...

I see Revit behaving this way, they regard the first point as ineligible to being tangent because it depends on the bearing of the line, With that assumption or bias, the first point is necessary to make a tangent condition possible. I can easily snap to a location on the circle (a pulley for example) that couldn't be tangent to the next pulley.

AutoCAD deals with this in a clever fashion (when we invoke the tangent snap) by fixing (changing) the first point to be tangent after the second point is placed. If we aren't careful with our second pick point (snap tangent too) the tangent line might end up on the opposite side of the pulley.

In contrast, Revit handles it naively, because it regards our first point as ineligible to tangents because it isn't considering this particular end result: "I want to draw a line tangent to two circles". AutoCAD appears to know this by virtue of snapping tangent for the first point so it can adjust the final bearing, and attachment to the circle, of the line.

To get around this naiveté, I place the first point on the pulley where it looks like it can be tangent, to my eye. The second point snaps to tangent with the icon. I return to the first point and grip/drag it away and back to let the snap icon appear, to fix it for tangent, just to see if I was close. If my guess wasn't accurate, it is now.

After reading a reply to my comments I did a quick sketch in AutoCAD and then did the same sketch in Revit using the same pulley sizes and offset from one another (see Footnote). The tangent lines have the same x/y properties for start and end as the AutoCAD version, that I made using its snap tangent.

This is the native DWG sketch and properties screen captures for each element.

This is same information but for the Revit drafting view exported to DWG. When I create an External Reference of the exported Revit drafting view it lands right on top of the native sketch. If you look really closely you'll see a value is slightly different in the Revit version. I think that might be my fault, sketching. Regardless, I think close enough is fair.

Footnote: Regarding a drafting view aligning with a DWG file after export: It might not be obvious but drafting views have an origin. To test that claim link a DWG, that has a marker at the WCS origin, into one and you'll see where the origin is. I did that before I did any sketching so I'd know how to place the pulleys in the same place. That made it possible to compare the tangent lines after exporting it to DWG.

Also the Start and End X/Y values are reversed. That's either just how Revit interprets the vector of each line segment or it's because of the direction I chose to sketch them in Revit. In AutoCAD I started at the smaller pulley. I didn't make sure to sketch in the same way in Revit, sloppy scientist.

By Sketch Stairs and using Stair Path and Tread Number Annotation Tools

Since they revamped the stair tools in Revit 2013 and tweaked them slightly in 2014 and 2015 we've had two annotation tools, Stair Path and Tread (or Riser) Number, to place view specific stair annotation.

Sadly the Stair by Sketch method of creating stairs is not recognized by these relatively new stair annotation features.

You'll find Revit is unresponsive when you attempt to apply them to your stair. They only work with Stair by Component. However, we can create a Stair by Component and then use Convert to turn each run/landing into a sketch based component and the Stair Path and Tread Number tools continue to work.

I assume this limitation has something to do with built-in locations within the component stair elements to define where the annotation can appear. There is no way to provide equal representation within the sketch. For them to work on the sketch based stairs I imagine it would be necessary to add another type of sketch element like Stair Path and/or RiserTread Path, like we already have for Run, Boundary and Riser. Using Convert on a stair component allows for sketch based modification but retains its componentness, at least enough for the annotation tools to keep working.

For now it may suffice to start with Stair by Component and then use Convert to modify the sketch as required. Worth a try.

Dept. of Off Topic - openingdesign.com

Ryan Schultz with openingdesign.com has occasionally asked me to offer some feedback on what they are working on. They went live with their site in May. It isn't about Revit, rather collaboration in the A/E/C realm. Here's what their website says:

...snip
OpeningDesign.com is a collaboration platform for A/E/C professionals—offering a real-time sketching and markup tool, and a place building and construction professionals can exchange expertise.
...snip

On their home page it discusses "The Tool" and "The Network". Regarding each it describes a problem and their solution.

The Tool:
...snip The Problem: On the phone, it's often difficult for A/E/C professionals to communicate a ‘visual idea' to another member of the team—whether it be a change to a floor plan, or small amendment to a shop drawing detail....snip

...snip The Solution: SketchSpace is an online tool that allows you to upload a PDF and sketch or mark-it-up, in real-time. If someone draws a circle around a foundation detail in New Orleans, the same circle instantly appears in Chicago, or Singapore for that matter. We like to think SketchSpace is the digital equivalent of having your entire team huddled around a set of CD's. Give it a try... ...snip

It's this SketchSpace you can experiment with now and it's pretty neat. They are looking for feedback to help expand and improve on its current capabilities.

The Network:

...snip The Problem: Unlike larger A/E/C firms, smaller firms do not have the luxury of a broad and deep pool of in-house experts they can consult for help....snip

...snip The Solution: Although it's not quite ready yet, we are currently developing OpeningDesign.com into a community platform where A/E/C professionals can collaborate and share expertise with other fellow building professionals. Whether it's getting help on a building code question, or soliciting feedback on a schematic design idea. Shoot us your email and we'll let you know when its up and running... ...snip

They've got a video on their site to help get a sense of what it's all about.

What is OpeningDesign.com? from OpeningDesign.com on Vimeo.

Sketch Again

No I don't have a new plug-in to create that napkin sketch look in Revit, sorry! I did write a post in January 2008 to describe a neat technique that the Introducing Revit Architecture 2008 book showed in a couple images. I made my own examples, like this one.



When Revit got its start, round about tens years back, one of the intentional concepts it hoped to bring back to us is sketching. Again not necessarily the napkin-sketch-look but at least the idea that we can draw something without being too hung up (at first) with accuracy, exact dimensions or precise wall types.

You can draw walls that loosely define rooms/volumes/spaces and shapes. After messing around with the general form and arrangement you can force more rigor or rules on the concept. You know, like a grid layout, masonry brick/block coursing/modules or assumptions about minimum clearance or sizes. I still encounter users now and then that start out by drawing "lines" to decide where walls should go. No, No...missing something big here...

The key thing to appreciate is that you can just sketch first and refine next/later.

I realized shortly after starting to use Revit that I was conditioned to try to draw really accurately FIRST with AutoCAD and Microstation because it was a pain to adjust things. Don't get me wrong, some change is painful even in Revit. Completely throwing out a concept will inevitably require a lot of rework. Starting with a rectangular building and switching to an oval probably isn't going to just update nicely, completely.

With Revit routine adjustments to clean up a concept IS much more friendly. Some of the tools that let you refine your work are temporary dimensions, permanent dimensions, levels, grids, reference planes and parameters, editing tools like move, align, rotate, the Type Selector and a little smarts and intuition thrown in.

To support the somewhat arbitrary state of ideas that are not fully formed yet you can also work with placeholders for walls, doors and windows etc. This means that you CAN draw a nominal wall that is 4 inches (100mm) or 6 inches (150mm) or even 8 inches (200mm). We don't need anything bigger than that do we?? 8-)

As the design get resolved you can replace these nominal walls with ones that represent framing sizes, gypsum wall board choices and even finishes if you choose to. One excellent suggestion that I think was first offered by Phil Read in a session at Autodesk University several years ago is to use specific materials for all generic "placeholder" elements. He suggested a common color that used some sort of transparency setting so they were clearly different from "real/resolved" things. Since we tend to spend a fair bit of time looking at the model in 3D views with Revit these unresolved elements stand out in the crowd.

To further explain this stuff I recorded a short video embedded here and posted at OpEd Videos and You Tube.

Sketching in AutoCAD

Autodesk recently made a new sketching add-on available to AutoCAD, made possible via their Alias sketching technology. Lynn Allen, on her blog "Lynn Allen's Blog", provided a link to a YouTube video of an artist using the new features. It does create some serious feature envy. Watch and imagine using it in Revit elevations to dress them up for a presentation, or any other view for that matter?

Want to watch the video here instead?

Revit MEP - Temporary Dimensions/Dimensions

There seems to be some inequity in the implementation of dimension behavior with Revit MEP. When we use RAC and RST we find that we can use temporary or permanent dimensions to reposition most elements.

With RME however Revit does not conduct itself in the same fashion. As an example we need to just look at a pair of ducts that are parallel to each other. A dimension placed between them does not become editable when you select either duct, nor does the Activate Dimensions button appear on the Options Bar. No temporary dimension appears between them.

It is as if it has been determined that behavior that most Revit users have come to expect isn't relevant or appropriate in RME for some reason. The lack of this make it more tedious to place duct work precisely relative to other duct. An exception to this is when two parallel ducts are not connected to each other via another duct.

It is my humble opinion that this deserves another look by developers.