autocad pankaj

8/2/2019 autocad pankaj

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ATTDISP

Function:Globally controls visibility of block attributes in a drawing

View menu:Display Attribute Display

Command entry:attdisp (or 'attdisp for transparent use)

Enter attribute visibility setting [ Normal /ON/OFF] :The drawing is regenerated after one changes the visibility unless

REGENAUTO, which controls automatic regeneration, is off.


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The current v isibility of attributes is stored in theATTMODE system variable.

Normal Retains the current visibility of each attribute. Visibleattributes are displayed. Invisible attributes are notdisplayed.

On Makes all attributes visible.

Off Makes all attributes invisible.


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AutoCAD 2007 provides three basic methods for creating surfaces the 2D Solid,3D Face and Region commands. The three commands were developed parallelto the historical development of the different types of computer modellers.

2D Solid: The first generation surface command available in AutoCAD. Usedmostly to fill an area in the sketch plane of the current UCS. This type of surface is not a true 3D surface.

3D Face: Creates a true 3D planar surface (allowing X, Y and Z coordinates) of three-sided or four-sided shape. This is the type of surface developed primarilyfor creating faceted surface models.

Region: Creates a 2D surface of arbitrary shape from existing 2D entities. Thiscommand creates the most flexible and the most complicated type of surfaceavailable in AutoCAD. This command was developed to allow manipulation of 2D surfaces using one of the solid modeling construction techniques, namely,the Constructive Solid Geometry method.


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3D InterfaceAutoCADs 3D Interface consists of three mainareas

The dashboardAnchored palettesA 3D workspace


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3D Dashboard

The dashboard consists of a set of control panelsorganized by function.

For example, the top control panel containscommands that create and modify 3D solids; thesecond control panel contains commands andcontrols used to navigate 3D models.

Click on any one of the panels to expand thedisplay to show a slide-out panel that hasadditional controls.


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3D Viewports


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Working with a 3D model has many advantages over 2D representations, including:Ease of visualising from any view point.

Ease of creating 2D draughting views.Creation of photo-realistic images, animations and virtual reality presentations.Use of geometry for computational analysis, e.g. FEA.Use of geometry for CNC manufacturing processes.

3D CAD offers tools to work not only on a plane, along the x and y axes as with2D CAD, but also in 3D space along the z axis, giving depth to the drawing. Thethree primary types of 3D modelling are :

WireframeSurfaceSolid


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Specifying and using coordinatesystems in 3D space.The WCS:

When one uses the snap tool, the pointer jumps around on an invisiblegrid system, enabling you to quickly place the pointer precisely onpoints of that grid.

The snap grid system lies on a flat surface defined in space by thecurrent coordinate system.

The primary coordinate system used to define this plane is called theWorld Coordinate System, or WCS, and its x and y axes define the planeitself. The WCS is the absolute reference AutoCAD coordinate system

The UCS:One can define own coordinate systems, make them current and usethem as aids to editing geometry, etc. These types of coordinatesystems are called User Coordinate Systems, or UCSs.


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WireframesA wireframe model is a skeletaldescription of a 3D object. Thereare no surfaces in a wireframemodel; it consists only of points,lines, and curves that describe

the edges of the object.One can create wireframemodels by positioning 2Dobjects anywhere in 3D space.AutoCAD also provides some 3Dwireframe objects, such as 3D

polylines (that can only have aCONTINUOUS linetype) andsplines.


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Surfacing in 3D.Surfaces, mathematicallyspeaking, have no thickness.They do however have twosides (or faces) and they haveedges (or boundaries).

They can be shaded andcan be used to provide goodvisual representations of solidobjects.

Surface modeling is moresophisticated than wireframemodeling in that it definesnot only the edges of a 3Dobject, but also its surfaces.


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Solid modelling.

Solid modelling provides the same displayinformation as surface and wireframemodelling. It also offers the advantage of representing the entire volume of thedesign.

The model can therefore be analysed forvolume related properties such as mass,moments of inertia, center of gravity, andthe model data can be used for 3D CNCmachine programming and 3D FEA.(Investigate what FEA is, perhaps using theinternet.)

Primitive solids.Composite solids.Extruded and revolved solids.


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Visual StylesA visual style is a collection of

settings that control the displayof edges and shading in theviewport.

1. Open a drawing with 3D objectsand display in a 3D view.

2. Choose View, Visual Styles andone of the following styleoptions.

2D Wireframe3D Wireframe3D HiddenRealisticConceptual


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3D Faces

3DFACE creates a three or four sided surface anywhere in 3Dspace. One can specify different Z coordinates for each cornerpoint of a 3D face.3DFACE differs from SOLID, which creates a three- or four-sidedsurface that is parallel to the current UCS and can be extruded.

1. Type 3DFACE at the command prompt.Command: 3dfaceFirst point: pick

Second point: pickThird point: pickFourth point: pickThird point: enter


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3D WIREFRAME LINES 3D FACE


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3D Move

Command entry: 3dmoveDashboard: 3D Make panel, 3D MoveSelect objects: Use an object selection method and press ENTER when you finishSpecify base point or [ Displacement ] : Specify a base point orenter dSpecify second point or : Specify a point orpress ENTERIf you are working in a viewport with 2D Wireframe set as the visual style,3DMOVE temporarily changes the visual style to 3D Wireframe for the durationof the command.The move grip tool is displayed at t he specified base point. For more informat ionabout using the move grip tool, see Use the Move Grip Tool to Modify Objects .Click an axis handle to constrain the movement to an axis.The two points you specify define a vector that indicates how far the selectedobjects are to be moved and in what direction.If you press ENTER at the Specify Second Point prompt, the first point isinterpreted as a relative X,Y,Z displacement. For example, if you specify 2,3


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for the base point and press ENTER at the next prompt, the objectsmove 2 units in the X direction and 3 units in the Y direction from theircurrent position.Realigning the UCSYou can press CTRL+D to turn on the dynamic UCS to realign the griptool as you move the pointer over faces, line segments, and polylinesegments. The grip tool orients the workplane depending on which edgeof the face the pointer crosses. You can click to place the grip tool (whichwill constrain the direction of the move operation). Specifiedcoordinates are relative to this workplane.Pressing CTRL+D again to turn off dynamic UCS before placing the grip

tool reverts the grip tools orientation to match the static UCS. DisplacementSpecify displacement : Enter coordinates to represent avectorPlaces the move grip tool at the origin (0,0,0). The coordinate valuesthat you enter specify a relative distance and direction.

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