Shocking Family Secrets Revealed

April 8th, 2014

Introduction

The following topics in this article are a culmination of years of secrets that I have used to build my Revit families. Most of it has been shrouded in secrecy. I have kept the secrets to myself, but I want to finally take this opportunity to share them with the Revit community. Read on and enjoy!

How to Cut the Long Sides of Beams

How do you cut the long side of a beam using the cut command and a reference plane when Revit only allows you to cut the short side of the beam? This is illustrated in Figure 1.

Figure 1: How to cut the long end of a beam

I have seen this question asked again and again on different Revit Forum Sites and I thought it was time to explain how I have done it in the past.

Follow the steps below and watch the scrolling image to learn how.

  • Draw a reference plane at the far end of the long side of the beam to be cut.
  • Cut the beam with the cut command.
  • Move the reference plane to the desired location and presto the long side is now cut!

Why did the Revit developers only allow users to cut the short side of the beam by a simple cut and pick command? I don't know, but I am sure the Revit developers had their reasons for making this the current workflow.

IMHO: The important thing to remember when solving Revit problems is to take matters into your own hands, and find ways to solve these problems yourself. Don’t wait for the Revit developers to change the program. Instead, change your way of thinking about the program. Having a positive attitude has always helped me solve my Revit problems.

For example, when I solved this particular problem, I didn't get angry at the Revit developers for making this limitation. I thanked them for programming in Revit the ability to MOVE a reference plane, which ultimately helped me solve this problem. Thank you, Revit Developers!

The Jet Engine

The following will show how to make the shape of the jet engine. The jet engine was used as part of the 747 jumbo jet modeled in Revit shown in Figure 2.

Figure 2: The Revit 747

How do you make a 747 engine when the profiles that are selected result in the following form?

Well, the developers did not allow profile order to be selected when creating a form. So should you give up, or wait for the developers to add that feature? Right! Take matters into your own hands and create the form, them MOVE THE PROFILE! Follow the steps shown in Figure 3.

Figure 3: How to move profiles of forms

“Ride the Rail” Rotation Method

Figure 4: The traditional rotation rig

The traditional method, shown in Figure 4, uses the angular dimension command. It is not a secret that it has been known to sometimes break at a zero value and at other angles. Because of this, I have created an alternative rotation method called “Ride the Rail” for use in the mass and adaptive component family environment.

Figure 5: Ride the Rail rotation rig

As shown in Figure 5, the rotation rig, Ride the Rail method does not use the angular dimension. Instead, it uses the power of the reference point to “ride” the “rail” of the circle or curve to control the angle. The next section will show an application of the Ride the Rail rotation method. 

Introduction to Inverse Kinetics

Let’s use what we just learned about the Ride the Rail rotation rig and apply it to a piece of construction equipment, shown in Figure 6 to animate the “arms.” This is the same concept as creating bones to drive the motion of character.

Figure 6: The Revit lift family

To make the bones in Revit, simply create a circle on each successive rotation point and make the element span between these points. This will result in a series of hosted Ride the Rail rotation rigs.

Draw a reference circle whose center is on the first center of rotation.  Then draw a circle where the radius is as large as the next closest rotation point as shown in the figure below.

Continue to draw circles at each node as shown in the previous step until all the joint locations have nodes with reference circles as shown in Figure 7.

Figure 7: Hosted rotation rigs

  • To add an angle parameter to each swing rig, select the hosted node on the circle and change the measurement type to angle and assign or create an angle parameter.
  • To add length parameter, do not use an aligned dimension. Take advantage of the rotational rigs that were just created. Since each segment of “arm” spans from hosted node to hosted node, then to make the “arm” longer just make the radius of the circle a parameter.

Because this is a piece of construction equipment, there will need to be some limits on the parameters that were just assigned. These booms are not allowed to move past a certain point as spelled out in the equipment specifications. Therefore, it is important to add some sort of limitations to the parameters. The fastest way to do this is simply “cut” the circle so that it results in an arc that starts and stops at the limits of the equipment as shown in Figure 8.

Figure 8: Limiting the rotation of the rig

“Revolve” Rotation Method

The Ride the Rail method has one drawback: It is not able to be used in the traditional family environment. However, when you apply the principle of the Ride the Rail method to a “Revolve” in the traditional family editor as shown in Figure 9, you get the same result.

Figure 9: Ride the Rail versus Revolve Rotation method

It was this fundamental concept that had me realize that the Revolve element could have a constant angle value and have its start and end angles move together. Also, you are able to define the end of an open revolve element as a work plane. Yes!

Figure 10: Revolve Rotation method

From this I created the “Revolve” rotation method as shown in Figure 10. Note that it uses the preset revolve form parameters of the start and end angles to control the angle—NOT the angle dimension.

The Revit Pumpkin

In this section we will learn how to model the Revit pumpkin as shown in Figure 11. I built the Revit Pumpkin as an entry in a pumpkin modeling contest (http://buildz.blogspot.com/2011/10/happy-halloween-iii.html) and I won first place for scariest pumpkin!

Figure 11: The Revit Pumpkin

  • Open up a new adaptive component family. Insert an image of the side view of a face in the left view of the elevations. Sketch in profile 1 first using the spline thru points command. It should look similar to Figure 12. I chose not to follow the shape of the face exactly since I was already using the “approximate” method. Also, the face was just a guide.

Figure 12: The profiles

  • Create the rest of the profiles 2, 3, 4, 5, and 6 in the same view using the previous method.
  • Create reference lines in a radial pattern and place the profiles with the dimensions shown. The profiles will be located at 5 degree intervals except profile 3 and 4, where they are located 2.5 degrees off of profile 2.
  • Copy profile 1 and paste it into the new adaptive family. Since the profiles were built in the “left” elevation view, then all the profiles will need to be separately pasted to the plan view and “rotated” into place.
  • Copy profile 2 and paste it into the Revit family. Repeat this process until all the profiles are created. Go back to the plan view and copy and mirror all six profiles.

Figure 13: The plan view of profiles

  • Select the 13 splines shown in Figure 13 and click “create form.” The final model should look similar to Figure 11.

The Revit Cow

You will be shown how to model The Revit Cow, shown in Figure 14. This example illustrates how I used Revit and other software to create the Revit Cow. However, this does not mean that you have to choose the software I was using. What is important is that you follow the fundamental steps that are involved no matter what software you are using.

Figure 14: The Revit Cow

Instead of creating the cow model from scratch, which was how I modeled the Revit Cow originally, just take pictures of a cow out on the farm and load it into 123 D Catch, which is free from Autodesk and make our own Cow model using the .obj extension. 

Open the .obj file in Autodesk® 3ds Max® and delete any extra mesh or vertices. Save the model and export the file as a dwg.

Open Rhino and import the exported cow from Max as a dwg format into Rhino. Select the dwg (mesh) and use the “mesh to nurbs “command.  Draw a plane that cuts the cow and go to a side view and replicate by array the planes as shown below. Select the planes and cow and use the “intersect” command. This will create all the profiles necessary to make a form in Revit. The profiles are radial from the back feet to the middle of the cow as shown in Figure 15. This was set up so that when the form is created in Revit there is less chance of it being successful because there are “smooth” transitions between each adjacent profile.

Note: You could alternatively use 3ds Max to create these profiles by using the spline intersect function.

Figure 15: Slicing up the profiles of the cow

Once the cow profiles are imported into Revit, simply select the spline thru points command and click the ends of each straight line segment. Repeat for each profile until all the profiles are completed as shown in Figure 16. With all the reference lines selected, click the “Create Form” button.

Figure 16: The Revit Cow Profiles and Nodal Points

This is only one half of the cow. If you want to make the other half simply mirror the forms at the centerline of the cow and it will create two halves that make a whole cow. Now that you have seen how all these families were created by revealing their secrets, go out and make some shocking families.

So that does it for this installment of Shocking Family Secrets Revealed. Good luck!

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About the Authors

Marcello Sgambelluri

Marcello Sgambelluri is the BIM Director at John A. Martin & Associates Structural Engineers in Los Angeles, CA. He has been using Autodesk products for more than 15 years including AutoCAD, 3ds Max, and Revit Structure. Marcello is devoted to helping advance the use and knowledge of BIM solutions within the AEC community. He frequently presents at Autodesk University and The Revit Technology Conference. He can be reached at marcellojs@johnmartin.com.

 

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