Lesson Plan: Drafting and Design J6-2

What is 3D solid modeling? How do 3D solid modeling programs work?

Boolean operation digital platform direct input entry primitive geometries sweeping texture map 3D extrusion 3D solid modeling

A. 3D solid modeling is the process of constructing complete geometric forms that can have surface and core properties. 3D modeling uses computer software to create three- dimensional virtual forms from geometric or mathematical input.

The solid modeling software has the ability to apply properties to the exterior and interior of the model. 1. A person can rotate 3D models completely around so the design can be explored from all perspectives. 2. Portions of the model can be removed, pulled apart, or joined to understand how the design works.

B. 3D models have a tremendous advantage over 2D drawings when it comes to building or machining and to understanding the fabrication process. Solid modeling also has an advantage over plain surface modeling as the object contains internal properties or mass. 1. Much of the machining industry uses a solid form of a material that is shaped or extruded into a product. 2. Having the data of a solid model allows machining mills or tools to calculate the necessary processes to fabricate a design. 3. The data in solid models can be used for rapid prototyping, which is a modeling process used in product design, manufacturing, and the medical industry.

C. The form of solid models can also be generated from digital data. This process of forming is based on parametric modeling. 1. Data input can arrive from any source. 2. Solid models are used to study, predict, and experiment with information. Meteorologists; architects; engineers; and physical, social, and behavioral scientists use them.

D. 3D solid modeling software is efficient to use and can be easily integrated across digital platforms. A digital platform is the electronic media, software, and interface used to exchange digital information. Advanced 3D modeling software allows for full integration. 1. Files can be converted into various formats to be shared for multiple uses. 2. Mathematical data from one source can be input into the 3D modeling software. The software then converts the data into a 3D form. 3. The accuracy of the 3D model allows for precision in fabrication and manufacturing.

A. Modeling programs can build 3D solid models in several ways. The two primary ways are to extrude the form from a 2D line drawing or to use primitive 3D geometries. A 3D extrusion (in CAD) is a form or shape created by pushing or pulling a 2D geometry along a third axis.

Primitive geometries are basic forms that include spheres, squares (or rectangles), cones, pyramids, and cylinders. 1. To create 3D extrusions from 2D line drawings, a line drawing is created and then imported into the 3D software.

2. A 2D line drawing is usually imported at a 1 to 1 scale, so the model will be its real (virtual) size. The 2D geometries can be extruded up or out into 3D. a. First, the 2D drawing must be traced. b. Second, the traced geometry is extruded into a third dimension for its height or length. 3. Basic 3D modeling has the option of direct input entry or physical adjustment of the shape with the aid of a mouse or tablet. Direct input entry is the process of applying geometric dimensions to 2D or 3D objects through numeric input.

B. Primitive geometries 1. It may be appropriate and efficient to create some 3D forms by using primitive geometries, which involves several basic steps. The geometries can be used in conjunction with other geometries or forms to create more complex objects. A Boolean operation is the process of intersecting multiple 3D forms that result in a union, a difference (subtraction), or an intersection.

2. When two geometries are joined together, a union is created. The combination of the forms creates a new 3D solid model. 3. One geometric form can be used to subtract or remove a portion of another form. In this case, the two are intersected, and one is used to cut away or subtract the difference from the other. 4. The Boolean operation can be used to intersect two geometries and may use the area where they overlap to generate a new solid form. The shape of the intersection of the geometries becomes a third geometry, or form, in this case.

C. A hand sketch can be used to generate a form. First, the sketch is scanned into the software. Once imported, dimensions can be applied, and 3D geometries can be extruded.

D. Sweeping (in 3D modeling) is the process of running a 2D geometry along a path to create a 3D volume. The modeling technique allows an individual to draw a path in the model space or to use the edge of an existing form and run geometry along the path to develop complex forms. 1. Sweeping may be used to erase a portion of a 3D volume. 2. The 2D object is a cutter that is run along a path inside another form. The intersection is removed; this is similar to how a cutter works in milling and manufacturing.

E. The geometries and forms created in 3D software have no physical properties, other than a shape, until they are applied. 1. A texture map is an image of a visual and often tactile quality applied to the surface of a model. The texture can be applied as a texture map or as a real 3D- created texture. 2. The surface can have lighting attributes applied to it. The attributes can range in their degree and may be reflective, transparent, or dull. 3. Some software can apply additional physical properties, including density, stiffness, and malleability. They can be used for testing purposes and to see how they react to applied forces.

F. Rendering 1. To view the model and its applied properties, an image must be rendered. Most 3D modeling software has at least one basic built-in renderer. 2. Rendering software calculates all the lighting and material affects, including generating shadows, highlights, and surfaces that absorb light or reflect it with different levels of transparency or opacity. 3. The more realistic the 3D model, the more time it requires to apply all the correct surfaces and lighting properties. It also takes much longer for the renderer to generate the realistic image.

What is 3D solid modeling? How do 3D solid modeling programs work?