Geometric Point Manipulation: Parametrics Made Easy

You should always try to be as efficient as you can when making Revit families. Always try to keep them as neat and organized as possible. Sometimes doing things the quick way can cause issues and take up more time down the road if updates are needed.

When creating families for Revit content it is important to get the most out of your models. Sometimes it’s more efficient to have one parametric family that contains twenty configurations rather than twenty static models: it helps to lower the impact on your project’s file size and gets things running smoothly. Another bonus is that time is saved when making an edit: changing multiple families when they could have been one is a time-waster. However, if a family is not built properly from the ground up it can still have a big impact on your project.

There are quite a few methods that lead to more parametric models. One of the biggest impacts on file size is from having a large number of lines (or geometry). Keep in mind that Revit doesn’t just track each extrusion but every line they are created from, so it is best to keep that number as low as possible.

One way to build numerous products into a single family is to use multiple sets of geometry and visibility parameters. Say, for example, that you need a table family with differently shaped table tops. By using this method, you would make all the different table tops as separate extrusions and control their visibility through parameters. This may not always be the best approach: each additional table top drawn adds more file size.

Another, more economical, method includes having a single extrusion that is manipulated to change between different configurations. One way to accomplish this would be to constrain the points (edges) of the extrusion. For this example we will build a table family that will have multiple table tops all varying in size and shape. It’s best to start with the most complex version, or the one with the largest number of sides. We will start with an octagon and have it change into a hexagon and then to a square.

  • The easiest way to start this extrusion would be to use the polygon tool to draw an eight sided shape.
  • Draw reference planes at every intersection where two lines meet. There should now be a total of ten reference planes, including the Center Left/Right and Center Front/Back if drawn in plan view.

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  • Now you can constrain all of the points of the polygon to their respective planes. Consider this creating an axis for each of the points. Keep in mind that at an intersection of two lines only one needs to have its point constrained.
  • Draw dimensions between the outer reference planes to set the overall width and depth of the table top.
  • Set dimensional parameters from the inner reference planes to the outer ones. These will be the offset parameters that allow you to control the number of sides on the table. To change the table top from an octagon to a hexagon, we just need to reduce the right and left offset parameter to zero. Similarly, if we want a square top we need to also change the front and back offset parameter to zero. This allows us to manipulate extrusions a little more by controlling the number of sides of our polygons: complexity of the geometry is altered using only length parameters.

Image 2Image 3

Another way to make families more parametric is through the use of nested families. Nesting families is a great way to save time and add more functionality to your models – but using nested families also brings up your file size quite a bit. Nesting a lot of families into one model can quickly bloat file size, especially when there are families nested several levels deep (nestception). If a nested family is needed it is best to have as few of them as possible. Try to make your nests as efficient as you can, since one complex nested family will have less of an impact than multiple simple ones.

For complex models, getting lost in your reference planes is a common issue. There are a few solutions for this as well. If you have overlapping planes, it is best to name the individual planes so you can keep track of what is locked to which plane. You also have the option to constrain within the extrusions by drawing reference planes within the sketches. When you do this, the reference planes will not be visible outside of editing the extrusion. When constraining inside the sketch, make sure that you don’t find yourself drawing redundant reference planes. Also, one of the major issues to watch out for is if someone else is trying to modify your model, it might not be apparent to them that the reference planes are there. If someone tries to constrain geometry (that is already constrained inside the sketch) to an outside plane, then they will start to get over constraint issues. It is always best to try and make the families in such a way that anyone can open it up and make changes without any prior knowledge of the model.

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