Three reasons for AutoCAD "truss fabrication"
in the last article, I briefly mentioned a small example of AutoCAD 3D modeling (truss production), but I didn't expect that some friends soon wrote to me that they didn't understand my way of truss production and had questions. I feel that this can be my problem. Maybe I didn't explain some problems thoroughly, and I feel it's not easy to write an article. Therefore, I would like to take this opportunity to analyze several issues. I hope I can make it clear this time. I have summarized the following questions: how to change the 3D viewpoint? Why use UCS? What is the significance of building tetrahedral frames at first
first of all, I want to tell friends who want to know about 3D viewpoint switching. It's very simple. You can select the view/toolbars/viewpoint option to open the viewpoint toolbar to make the polishing damage layer shallower (or right-click on any toolbar, and the toolbars dialog box will pop up to select viewpoint) as shown in the figure:
this toolbar successively includes the top view, bottom view, left view Right view, front view, back view and other four isometric views (southwest, Southeast, northeast and northwest), you will find that only in the isometric view, our screen space is three-dimensional. We can choose four isometric views in turn, and it feels like the viewpoint rotates around the three-dimensional model. Note that the basic direction in the figure is the same as that in the general map, that is, north facing up. In addition, we can also use the zoom realtime option to zoom in and out of the view in real time, and select the menu view/3d viewpoint/tripod option to arbitrarily change the viewpoint angle of the view. Do you feel a little bit. I think the first question can be put aside
then let's think about why we need to use UCS coordinates. I think we are used to drawing in plane coordinates at any time. At least I am. We know that the reason why a plane is a plane is that it has no z-axis coordinates. My understanding is that we build a three-dimensional model. The part of the plane needs to be completed in X and Y coordinates, and the three-dimensional operation is the operation of the z-axis; Therefore, can we say that the UCS we need is that the specimen is disc-shaped in order to define the X and Y planes of various angles and positions, and the Z axis of each UCS provided to us for three-dimensional operation. Take the truss for example. I define a UCS user coordinate for each truss beam in order to easily draw its cross section in the X and Y planes of each UCS. It is natural to say the last question here. I use each side of the tetrahedron to locate the direction of the Z axis of each truss beam, and complete the assignment of the Z axis length by clicking its starting point and total point. I think it should be clear when I look back now
well, let's look at the main cartons and see how to establish UCS. Let's open the view/toolbars/ucs option, as shown in the following figure
all the options are used to establish UCS coordinate system. Is it necessary to explain each option in detail one by one? I don't think it's necessary. I always think practice is a very important learning method. It's necessary for everyone to practice one by one. In fact, we don't have to remember every usage. I really can't remember it, but I'll try to remember several options that I think are easier to use and familiar. For example, the ninth option defines a UCS coordinate system according to the direction of the Z axis, which was used in the fabrication of trusses, remember?; In addition, the tenth option is also very useful. It uses three points to determine a plane to define the X and Y planes of UCS. I think the UCS option will be often used in our future modeling