![Johnson Lim© 2005 All Rights Reserved
More Examples
• You can also use this method to quickly draw
a rectangle of known size.
• Say you needed to draw a rectangle 20
drawing units wide and 10 drawing units high
and you didn't mind where exactly the
rectangle is drawn, you could do this:
Command Sequence
Command: RECTANGLE
Specify first corner point or
[Chamfer/Elevation/Fillet/Thickness/Width]:
(pick a point near the middle of the drawing area)
Specify other corner point or [Dimensions]: @20,10
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chapter 2 Coordinate Systems.ppt
- 1. Johnson Lim© 2005 All Rights Reserved Chapter 2 Coordinate Systems in AutoCAD
- 2. Johnson Lim© 2005 All Rights Reserved Using Coordinates… • A good understanding of how co-ordinates work in AutoCAD is absolutely crucial to construct drawings more easily. • Co-ordinates fall into two types, namely Cartesian and Polar. • These two co-ordinate types can be either Absolute or Relative. • Knowing just when and where to use the various types of co-ordinate is the key to efficient drawing with AutoCAD. Courtesy of CADTutor (2005)
- 3. Johnson Lim© 2005 All Rights Reserved Cartesian Co-ordinates • Named after the French philosopher and mathematician René Descartes (1596-1650) • Standard co-ordinate system • The position of a point can be described by its distance from two axes, X and Y. • This results in a simple point description using two numbers separated by a comma e.g. 34.897,45.473. Courtesy of CADTutor (2005)
- 4. Johnson Lim© 2005 All Rights Reserved Examples of Cartesian Co- ordinates Courtesy of CADTutor (2005)
- 5. Johnson Lim© 2005 All Rights Reserved Some extra… • AutoCAD allows you to use co-ordinates to draw objects rather than using pick points. • For example you could draw a line like this: • This sequence draws a line between the two co-ordinate points specified. Command Sequence Command: LINE From point: 34.897,45.473 To point: 54.896,65.395 To point: (press enter key to end) Courtesy of CADTutor (2005)
- 6. Johnson Lim© 2005 All Rights Reserved Polar Co-ordinates • Polar co-ordinates use one distance and one angle to describe the position of a point rather than the two distances in the Cartesian system. • The distance and angle measurements are made relative to an origin. Courtesy of CADTutor (2005)
- 7. Johnson Lim© 2005 All Rights Reserved Examples • This results in a point description which looks like 34.897<30 where the first figure is the distance (in drawing units) and the second is the angle. • AutoCAD angles start at 3 o'clock (i.e. along the positive portion of the X axis) and increase in an anti- clockwise direction. Courtesy of CADTutor (2005)
- 8. Johnson Lim© 2005 All Rights Reserved The UCS Icon • This is called the UCS (User Co-ordinate System) icon and it is there to remind you which is the X axis and which is the Y axis. • The empty box at the intersection of the X and Y axes is there to remind you that you are using "World" co-ordinates and that the UCS icon is not positioned over the true origin of the current co-ordinate system Courtesy of CADTutor (2005)
- 9. Johnson Lim© 2005 All Rights Reserved Absolute & Relative Co-ordinates • Both Cartesian and polar co-ordinates come in two flavors, absolute and relative. • The distinction is quite simple, absolute co- ordinates relate to the X and Y axes and the origin of the current co-ordinate system, whilst relative co-ordinates relate to the current pick point. • To specify a relative co-ordinate you need to use the "at" symbol as a prefix. • "at" symbol = @ Courtesy of CADTutor (2005)
- 10. Johnson Lim© 2005 All Rights Reserved Examples… • Relative co-ordinates are very useful for drawing objects which you know the size of. • For example, you could draw a square of 12 units with its lower left hand point at 30,40 as follows: Command Sequence Command: LINE From point: 30,40 (an absolute Cartesian co-ordinate) To point: @0,12 (a relative Cartesian co-ordinate) To point: @12<0(a relative polar co-ordinate) To point: @0,-12 (another relative Cartesian co-ordinate) To point: C (to close) Courtesy of CADTutor (2005)
- 11. Johnson Lim© 2005 All Rights Reserved More Examples • You can also use this method to quickly draw a rectangle of known size. • Say you needed to draw a rectangle 20 drawing units wide and 10 drawing units high and you didn't mind where exactly the rectangle is drawn, you could do this: Command Sequence Command: RECTANGLE Specify first corner point or [Chamfer/Elevation/Fillet/Thickness/Width]: (pick a point near the middle of the drawing area) Specify other corner point or [Dimensions]: @20,10 Courtesy of CADTutor (2005)
- 12. Johnson Lim© 2005 All Rights Reserved Display Controls • Display controls enables users to have easier viewing of their drawings. • These includes zooming and panning of drawings. • The commands include zoom, pan, redraw, regen, aerial view etc.
- 13. Johnson Lim© 2005 All Rights Reserved The Zoom Commands • Zoom Window : Select a window over the location to zoom into. AutoCAD will zoom in close to the object including everything within the selection box. • Zoom Dynamic : Enables the user to set the size of a standard zoom window type box, then use this box to select zoom in views of the drawing with this box with clicks of the mouse button. Courtesy of AutoCADCentral.com (2005)
- 14. Johnson Lim© 2005 All Rights Reserved Zoom Windows… Courtesy of AutoCADCentral.com (2005)
- 15. Johnson Lim© 2005 All Rights Reserved The zoom continues… • Zoom Scale : Enables the user to zoom into the drawing to a known scale • The value you enter is relative to the limits of the drawing. For example, entering 2 doubles the apparent display size of any objects from what it would be • If you enter a value followed by x, AutoCAD specifies the scale relative to the current view. For example, entering .5x causes each object to be displayed at half its current size on the screen. • If you enter a value followed by xp, AutoCAD specifies the scale relative to paper space units. For example, entering .5xp displays model space at half the scale of paper space units.
- 16. Johnson Lim© 2005 All Rights Reserved Zoom Command • Zoom Centre : Specify a centre point, then a radius and AutoCAD will centre this view to fit your screen. • Zoom In : zooms into the drawing slightly • Zoom Out : zoom out of the drawing slightly • Zoom All : Zooms to the extents of the drawing limits. Don't worry about this just yet.
- 17. Johnson Lim© 2005 All Rights Reserved The Zoom Command • Zoom Extent : One press will zoom to the extent of the entire drawing enabling a very quick overview of the project and an easy starting point to zoom into a more precise area of the drawing with one of the above tools. • Zoom Realtime : will zoom in and out of the drawing dependant on how far you move your mouse. Left click and hold the left mouse button down. AutoCAD will zoom in further into the drawing the further you move you mouse up (away from you). Try pulling the mouse down with the left button still held down, AutoCAD will zoom out.
- 18. Johnson Lim© 2005 All Rights Reserved Panning… • Concept: moving your drawing paper by hand • Drawings are neither zoomed nor scaled. • Pan Point : Require point to put and place • Realtime Pan : Can pan in real-time by holding mouse clicks.
- 19. Johnson Lim© 2005 All Rights Reserved Other Display Controls… • REDRAW/REDRAWALL: redraws the current viewport, removing marker blips and display artifacts (stray pixels) left by editing commands. REDRAWALL did the same thing in all viewports • REGEN/REGENALL: REGEN regenerates the entire drawing and recalculate the screen coordinates for all objects. It also reindexes the drawing database for optimum display and object selection performance. • REGENAUTO: drawings regenerate automatically. If you are working on a large drawing, you may want to set REGENAUTO to off to save time.
- 20. Johnson Lim© 2005 All Rights Reserved One last command… • VIEWRES: controls the appearance of circles, arcs, ellipses, and splines using short vectors. The greater the number of vectors, the smoother the appearance of the circle or arc. • For example, if you create a very small circle and then zoom in, it might appear as a polygon. Regenerating the drawing updates and smoothen the circle's appearance.