Introduction to forms. In this video, we'll explain BREP versus T-Spline surfaces and identify a form body. In Fusion 360, we want to get started with the supply dataset BREP versus T-Spline. In this design, we have a single sketch that contains two rectangles. We're going to talk about the differences between a BREP or a boundary representation and a T-Spline or a form body. To get started, we're first going to go to create, revolve, and select one of the sketch profiles. Then for the axis of revolution, just select one of the vertical edges and create a new body. We want to bring back the sketch, but we want to talk about the fact that this is a BREP body. A BREP body is a solid body that's comprised of individual faces on the external portion of the body. When we create a form body, we're talking about a subdivision that allows us to have minute control over various areas of the design. In order to create a form body, we need to select "Create Form". Once we do that, we have several creation tools at our disposal. We can create sketches in here, we can use primitives to define, we can create faces, or we can use some of our standard tools such as extrude, revolve, sweep, or loft. In this example, we're going to take a look at using revolve and using that closed profile on the right-hand side, one of the vertical edges for the axis of revolution, and simply note on screen the differences between the creation of that revolve in the solid workspace and the creation of it here in the forms. You'll note that we do have some options for the number of divisions, the way that the spacing is defined, whether or not we have symmetry. For this example, we're not going to add symmetry, we're simply going to create this new body, and then we can hide our sketch. In the bodies folder you'll note that currently this looks like a surface body icon, but it's purple and it has divisions on the face. Whenever we're working inside of the form toolset, as long as we have a closed volume, that closed volume will be converted back to a solid BREP. As soon as we have an open volume, that open volume will be converted to a set of surfaces. In this case, if we finish form, it looks very similar. However, you will note that there is a division on that top face. We have two solid bodies that really appear no different at all when we take a look at them in the browser. Then if we look at the timeline, you'll notice that we have our revolve, and then we have a form feature. It's important to note that forms do not capture timeline history, however, we can go in and use direct modeling tools to modify it. For example, if we right-click on the form and select "Edit". If I use modify, edit Form, I can select individual faces. I can select edges or I can select vertices. I can manipulate them by translating them, by rotating them, or by scaling them. There are additional tools that we can use but for right now, this is the basis of how we can manipulate these form bodies. If we finish form, we're still converted back to that same solid body. However, you'll note that it no longer looks like a cylinder. We do have the option to convert solid geometry into form geometry, but of course there are limitations. If we select "Create Form," we have an option under utilities to select convert. When we select convert, we have the option to convert T-Splines to BREPs, BREP faces to T-Splines or quad meshes to T-Splines. Quad meshes are going to be outside of the topic here, but we're going to take a look at BREP faces to T-Splines. We're going to select a face, and note when do I select a circular face that I'm getting a quad patch. The quad patch has four sides to it and simply is encompassing everything that we've selected. If I select a cylinder, however, that is converted a little bit more cleanly because it can be broken down into these quad patches. Now, we have two separate foreign bodies that are inside of this form feature in the timeline. These can each be manipulated by selecting faces, edges, or vertices, and using tools like edit form. When we finish the form, these are both converted into individual surfaces. These surfaces are modified inside of the form workspace, but converted back to a boundary representation when we come back into our design workspace. Keep in mind when we begin working with forms, this gives us more control over creating these organic type shapes, but we do have to always be mindful of how we're starting out our shapes, and what the end goal is. Whether it's going to be a solid or a surface it really doesn't matter as long as we follow best practices as we're defining them. At this point, let's make sure that we save this design before moving on.
