Create 3D Solid Objects

Create 3D Solid Objects by 2D Projection Views

Add 3D Thickness to Objects Lecture Five and Six 1 Overview of 3D Objects Add 3D Thickness to Objects 2 Create Wireframe Models 3 4 Create Surface Meth Models Create and Display 3D Solids in Viewports * 5 Modify 3D Solids * 6

1. Overview of 3D Objects 3D modeling has several advantages: 3D objects can be represented by simulated surfaces (3D thickness), as a wireframe model, as a surface model, or as a solid model. Three types of 3D modeling are supported: wireframe, surface, and solid. Each type has its own creation and editing techniques. 3D modeling has several advantages: View the model from any vantage point Generate reliable standard and auxiliary 2D views automatically Create 2D profiles Remove hidden lines and do realistic shading Check interference Export the model to create an animation Perform engineering analysis Extract manufacturing data

Overview of 3D wireframe objects A wireframe model is a skeletal description of a 3D object. There are no surfaces in a wireframe model; it consists only of points, lines, and curves that describe the edges of the object. You can create wireframe models by positioning 2D (planar) objects anywhere in 3D space. Some 3D wireframe objects are also provided, such as 3D polylines (that can only have a CONTINUOUS linetype) and splines. Because each object that makes up a wireframe model must be independently drawn and positioned.

Overview of 3D Surface modeling Surface modeling is more sophisticated than wireframe modeling in that it defines not only the edges of a 3D object, but also its surfaces. The surface modeler defines faceted surfaces using a polygonal mesh. Because the faces of the mesh are planar, the mesh can only approximate curved surfaces. With Autodesk Mechanical Desktop®, you can create true curved surfaces. To differentiate these two types of surfaces, faceted surfaces are called meshes.

Overview of 3D Solid modeling Solid modeling is the easiest type of 3D modeling to use. With the solid modeler, you can make 3D objects by creating basic 3D shapes: boxes, cones, cylinders, spheres, wedges, and tori (donuts). You can then combine these shapes to create more complex solids by joining or subtracting them or finding their intersecting (overlapping) volume. You can also create solids by sweeping a 2D object along a path or revolving it about an axis. With Autodesk Mechanical Desktop, you can also define solids parametrically and maintain associativity between 3D models and the 2D views that you generate from them.

About conversion of three modeling type Each modeling type uses a different method for constructing 3D models and editing methods vary in their effect on the different model types. It is recommended that you not mix modeling methods. Limited conversion between model types is available from solids to surfaces and from surfaces to wireframes; however, you cannot convert from wireframes to surfaces or from surfaces to solids.

2. Add 3D Thickness to Objects Thickness is a property of certain objects that gives them a 3D appearance. The 3D thickness of an object is the distance that object is extended, or thickened, above or below its location in space. Positive thickness extrudes upward in the positive Z direction; Negative thickness extrudes downward (negative Z). Zero (0) thickness means that there is no 3D thickening of the object. The thickness property changes the appearance of the following types of objects: 2D solids , Arcs, Circles, Lines, Polylines (including spline-fit polylines, rectangles, polygons, boundaries, and donuts) Text (only if created as a single-line text object using an SHX font)

3. Create Wireframe Models You enter coordinates that define the X, Y, and Z location of the object by using Line, Polyline and 3DPolyline command in X-Y-Z coordinates system. Setting the default construction plane (the XY plane of the UCS tool) on which you will draw the object and view it by view tools

4. Create Surfaces The surface modeler creates faceted surfaces using a polygonal mesh. Because the faces of the mesh are planar, the mesh can only approximate curved surfaces. The mesh density controls the number of facets on a surface, and is defined in terms of a matrix of M and N vertices, similar to a grid consisting of columns and rows. M and N specify the column and row position, respectively, of any given vertex. A mesh can be open or closed. A mesh is open in a given direction if the start and end edges of the mesh do not touch, as shown in the following illustrations.

Several methods for creating meshes (1) Create a Predefined 3D Surface Mesh The 3D command creates the following 3D shapes: boxes, cones, dishes, domes, meshes, pyramids, spheres, tori (donuts), and wedges by surface toolbar. To view the objects you are creating with the 3D command more clearly, set a viewing direction with 3DORBIT, DVIEW, or VPOINT. In the following illustrations, the numbers indicate points you specify to create the mesh and used tools.

(2) Create a Tabulated Surface Mesh With the TABSURF command, you can create a surface mesh representing a general tabulated surface defined by a path curve and a direction vector. The path curve can be a line, arc, circle, ellipse, elliptical arc, 2D polyline, 3D polyline, or spline. The direction vector can be a line or an open 2D or 3D polyline. TABSURF creates the mesh as a series of parallel polygons running along a specified path. You must have the original object and the direction vector already drawn, as shown in the following illustrations.

(3) Create a Revolved Surface Mesh Use the REVSURF command to create a revolved surface, also called a surface of revolution, by rotating a profile of the object about an axis. REVSURF is useful for surfaces with rotational symmetry. The profile is called a path curve, which can be any combination of lines, circles, arcs, ellipses, elliptical arcs, polylines, or splines, closed polylines, polygons, closed splines, or donuts.

(4) Create a Ruled Surface Mesh With RULESURF, you can create a surface mesh between two lines or curves. You can use two different objects to define the edges of the ruled surface: lines, points, arcs, circles, ellipses, elliptical arcs, 2D polylines, 3D polylines, or splines. Pairs of objects to be used as the “rails” of a ruled surface mesh must both be either open or closed. You can pair a point object with either an open or a closed object. You can specify any two points on closed curves to complete RULESURF. For open curves, construction of the ruled surface is based on the locations of the specified points on the curves.

(5) Create an Edge-Defined Surface Mesh With the EDGESURF command, you can create a Coons surface patch mesh, as shown in the following illustration, from four objects called edges. Edges can be arcs, lines, polylines, splines, and elliptical arcs, and they must form a closed loop and share endpoints. A Coons patch is a bicubic surface (one curve in the M direction and another in the N direction) interpolated between the four edges.

(6) Create a Rectangular Mesh With the 3DMESH command, you can create polygon meshes that are open in both the M and N directions (similar to the X and Y axes of an XY plane). You can close the meshes with PEDIT. You can use 3DMESH to construct very irregular surfaces. In most cases, you can use 3DMESH in conjunction with scripts or AutoLISP routines when you know the mesh points. In the left example of text on the command line, you enter the coordinate values for each vertex to create the mesh in the illustration.Example: .

5. Create and Display 3D Solids in viewports Viewports are areas that display different views of your model. As you work on the Model tab, you can split the drawing area into one or more adjacent rectangular views known as model space viewports. Viewports created on the Model tab completely fill the drawing area and do not overlap. As you make changes in one viewport, the others are updated simultaneously. Model space viewports are shown in the illustration.

Create 3D Basic Solids You can create solids from Solid tool bar box sphere cylinder cone wedge torus You can also create basic a solid shape by extruding a 2D object along a path or revolving a 2D object about an axis. Extrude and Revolve

6. Modify 3D Solids Once you have created a solid, you can create more complex shapes by combining solids. You can join solids, subtract solids from each other, or find the common volume (overlapping portion) of solids. UNION INTERFERENCE SUBTRACT INTERSECT

Modify 3D Solids by Slice and Section Command: _slice Select objects: 1 found Select objects: Specify first point on slicing plane by [Object/Zaxis/View/XY/YZ/ZX/3points] <3points>: yz Specify a point on the YZ-plane <0,0,0>: Specify a point on desired side of the plane or [keep Both sides]: -10,0,0 Command: _section Select objects: 1 found Select objects: Specify first point on Section plane by [Object/Zaxis/View/XY/YZ/ZX/3points] <3points>: xy Specify a point on the XY-plane <0,0,0>:

Modify 3D Solids and 3D Operation Color Face Shell Chamfer Fillet Mirror 3D 3D Array Rotate 3D Align Extrude Face

Example One 0f Creating 3D Solid Subtract Cylinder - Five Prism

Example One 0f Creating 3D Solid Slice command slicing plane by 3point Keep Both Side Cut Face One: Points 1-2-3 Cut Face Two: Points 2-3-4 Cut Face Three: Points 4-5-6

Example Two 0f Creating 3D Solid (1). Extrude (2). Rotate 3D 2D Projection Views (3). Align (4). Shade Gouraud (5). Intersection

Example Three of Creating 3D Solid (1) Box-UCS-move-Polyline 2D Projection Views (2) Extrude-Select-polyline

Process of Creating 3D Solid (3) Subtract Vertical Cylinder (4) Subtract Horizontal Cylinder (5) Wedge Mirror 3D Move (6) UCS-move Box Copy (7) Union Wedge Subtract Box (8) UCS-move UCS-rotate Box (9) UCS-move Polyline Extrude Mirror 3D (10) Union Box Subtract U-block

Example Four 0f Creating 3D Solid (1) Extrude Loop (2) Solidedit-Shell (3) Subtract Cylinders (4) UCS-new-3point (5) Box Mirror 3D (6) Subtract Boxes

Exercises Five After Class Creating 3D Solid by 2D projection views and dimensions

Exercises Five After Class (2)Creating 3D Solid by 2D projection views and dimensions