### Metric of solid

When calculating the dimensions of solid parts (Solid 3d), my plugins calculate and preserve the so-called metric of solid. The metric allows you to distinguish the details from each other and find the parts mirror to each other. If all the data in the metric is the same - then the program will assume that it is the same part. Although in fact there may be a mistake, because the accuracy of the calculations is limited.

Use the Lay, Saw, AVCNum or SolSize commands to measure solids. All these commands will record the results in xData of solids and you will see them in the Metric section if you install the Names plugin. The metric includes:
• Length - maximum of the three overall dimensions.
• Width - third of the three overall dimensions
• Thickness - minimum of the three overall dimensions
• Volume - real volume of solid (not product dimensions). In the millimeter drawing, the area will be converted into cubic meters.
• Area - the area of the greatest flat face of the part. You can use it to calculate the quantity of materials. In the millimeter drawing, the area will be converted into square meters.
• Perimeter - perimeter of the outer contour of the largest flat face of the part. You can use it to count the number of edges. In the millimeter drawing, perimeter will be recounted into meters.
• Faces - number of faces of the solid.
• Asymmetry - Indicator asymmetrical: the distance from the boxing center to the center of mass. It allows you to identify the offset holes, and others.
• AsymVector - The direction of the center of the box to the center of mass in three dimensions XYZ. It differs from the mirrored parts
• Technology - Method of manufacturing parts. At the moment, the algorithm is as follows: if you mark detail as a Sweep, the "Sweep" is written. For parallelograms without holes "Box" is written. If all the faces are flat and there are not more than six of them, then the "Saw" is written. If the faces are flat or cylindrical - write "Milling". Otherwise, "3D milling". Thus, in most cases, you can easily select the parts that can be made on a sliding table saw using tilt of saw blade. Or you can easily select details those that can be made on a 2D+ CNC-milling cutter. Of course, this simple algorithm does not cover 100% of the cases. Therefore, the results of this algorithm should be treated critically, the responsibility always remains on the engineer and technologist.

All these properties - read only. And they will all be zero, until the solid measurement is made. Call one of the commands: Lay, Saw, AvcNum or SolSize. Then the solid will be measured and the dimensions will be retained within the solid (in xData).  Now program can show the metric. Any change in solid, as well as in moving and copying, metrics will be reset to zero. And again you will have to call the measurement command. Automatic measurement is not implemented because it strong loads AutoCAD and takes a long time. After you change the properties of the SWEEP as required manually call one of the measurement commands too.

## Metric measurement rules

The measurement program is made for use in the design of sheet material parts. These parts always have a main plane, on which it is determined how to lay out the part. This algorithm does not work for spheres, tors, shafts and sculptural details. The program can measure the simplest sweep of bent parts, but they must be specially marked. To do this, you need the Names plugin.
The program is looking at each solid front (main) surface. This surface should be in the XY plane on the LAY command. When choosing a front side, surfaces are given an advantage in the following order of priorities:
1. Flat faces. If suddenly the program ignores the face, check that during the explosion it turns into a Region, and not in the Surface.
2. Faces having an oppositely directed pair. Thus, any inclined ends are discarded.
3. A surface marked with color (even if it is small). Thus, you can force the program to select the face you want.
4. Maximum in area. Thus, faces with blind holes and dadoes are sifted out.
5. The coating material is assigned. You can assign material to laminated or painted surfaces and they will be considered front side. But this will work when choosing one of two identical large surfaces. Thus, you can easily assign materials to the edges - the part will not stand on the end when laying out.
6. Initially turned up (top-side priority). This will help to lay out the details of the catwalks and floors. Also works only for the same largest surfaces.
Color marking and top-side priority can be turned off in Common Options.

In addition, the part rotate around Z so that the longest edge of the solid extends along the X axis (or Y if the Texture property is = Across). When searching for the longest edge, the priority of the right angles is taken into account. Those a rectangular triangle will not be laid along the hypotenuse. Only after laying and rotating the program measures the smallest box, which will fit solid. Dimensions of this box along the axes XYZ are considered the dimensions of the part. The largest dimension is length, medium - wide and least - thickness. The volume is also calculated only after the layout. AutoCAD can give different volumes when you rotate the same solid. The distance from the center of the box to the real center of mass of the part is considered an indicator of asymmetry. For simple boxes, this distance is zero. If the parts have identical metrics, but different directions of asymmetry - then it is considered that the parts are mirror to each other.
Note that the area and perimeter are not calculated for the entire solid, at the same time for one largest flat surface, which the program considers the base. Usually this is the area of the facade of the part.