Category / AutoCAD

by mikechristenson

AutoCAD: Importing and Exporting

TO EXPORT A MODEL OR DRAWING FROM AUTOCAD:

AutoCAD offers a small number of writeable file formats. The most versatile and useful of these are the DWG and DXF formats. Use AutoCAD’s SAVEAS command to export your AutoCAD work in several versions of these formats. (Note, for example, that some software cannot read a 2010 DWG or a 2013 DWG file, so that you may need to SAVEAS a 2007 DWG file to ensure legibilty.)

AutoCAD’s WBLOCK (Write Block) command is useful if you want to export just part of a drawing or model to a new DWG file.

AutoCAD’s EXPORT command is minimally useful: it allows you to export your AutoCAD information in one of a few non-AutoCAD formats.

 

TO IMPORT A MODEL OR DRAWING TO AUTOCAD:

To get the best results for importing vector information to AutoCAD, the vector information should be previously saved in the DWG or DXF format. Most modeling and drawing software (Rhino, SketchUp, Revit, Illustrator) can write information in one or both of these formats. Use AutoCAD’s File > Open command to open files of either type (DWG or DXF).

AutoCAD also has an IMPORT command which is minimally useful in opening files of non-AutoCAD format.

Edit > Paste can be of use in specific situations when copying and pasting vector information from one document to another.

by mikechristenson

Techniques for Reducing File Size

This page summarizes file-size reduction techniques for several software applications. File-size reduction strategies are usually directed toward managing the overall size of a package of documents.

NOTE: As a general rule, full-size (non-reduced) copies of important documents should always be archived and backed up: reduced-size copies are not usually meant as a replacement for full versions.

REDUCING FILE SIZE IN PHOTOSHOP IMAGES:

MANAGING LAYERS. A reduced-size Photoshop image, regardless of file type, should always be “flattened” into a single layer. Use the Layer > Flatten Image command.

MANAGING IMAGE RESOLUTION. Use the Image > Image Size command to adjust image dimensions and resolution. Images measuring approximately 5” or 6” in their longest dimension, with a resolution of 150 or 200 pixels per inch, usually represent a good balance between file size and image quality.

CHOOSING THE PROPER FILE TYPE. Generally, though not always, the smallest Photoshop files will be met by using the JPEG file type. Use the File > Save As command. Setting the JPEG quality to “Medium” will represent a good balance of size and quality. In the case of images with large areas of solid color, using the TIFF format (with LZW compression) will usually result in a smaller file.

REDUCING FILE SIZE IN ILLUSTRATOR DOCUMENTS:

CHOOSING THE PROPER FILE TYPE. Illustrator uses two different “native” file formats, AI and PDF. To reduce file size, use the File > Save As command to save your Illustrator file in PDF format. When prompted to choose an “Adobe PDF Preset,” choose “Smallest File Size.”

ADDITIONAL OPTIONS. Refer to this site for a detailed description of Illustrator optimization techniques:
http://helpx.adobe.com/illustrator/kb/optimize-native-pdf-file-sizes.html

REDUCING FILE SIZE IN PDF FILES:

COMBINING DOCUMENTS IN ADOBE ACROBAT. If you choose to combine files into a single PDF, click the “Smallest File Size” icon. Use the “Single PDF” rather than the “PDF Portfolio” option.

PRINTING AS THE SMALLEST FILE SIZE. Open a PDF in Acrobat. Choose File > Print. Select PDF as your printer (Adobe PDF or a PDF Writer). Click the “Properties” button. Under “Default Settings,” choose “Smallest File Size.” Click OK, and then click Print.

REDUCING FILE SIZE IN AUTOCAD DRAWINGS AND MODELS:

PURGING THE AUTOCAD DRAWING. AutoCAD drawings often contain unnecessary information (e. g., unused blocks, layers, text styles, etc.). Type PURGE at the command prompt to eliminate such information. Follow the PURGE command with the File > Save As command.

THE OVERKILL COMMAND. Type OVERKILL at the command prompt to delete certain kinds of information in the drawing, e. g., lines which overlap other lines.

FILE > SAVE AS. Use this command to save a new copy of your AutoCAD file. This will usually reduce file size.

REDUCING FILE SIZE IN REVIT MODELS:

PURGING UNUSED ITEMS. Under the Manage tab, Settings panel, choose Purge Unused. This tool will tend to have a greater effect on Projects than Families.

[APPLICATION MENU] > SAVE AS. Use this command to save a new copy of your Revit file. This will usually reduce file size. Test the effect of checking the “Compact File” option while saving (Click Options in the Save As dialog box).

REDUCING FILE SIZE IN RHINO MODELS:

PURGE THE MODEL. Type PURGE at Rhino’s command prompt.

FILE > SAVE AS. Use this command to save a new copy of your Rhino file. This will usually reduce file size.

REDUCING FILE SIZE IN SKETCHUP MODELS:

PURGE UNUSED. Choose Window > Model Info > Statistics; click Purge Unused. Follow this with File > Save As.

ELIMINATE TEXTURES. A copy of your model saved without textures will be much smaller than the same model with textures.

FILE > SAVE AS. Use this command to save a new copy of your SketchUp file. This will usually reduce file size.

 

 

by mikechristenson

AutoCAD: Inserting, Scaling, and Clipping Images

INSERTING IMAGES: AutoCAD can import Photoshop-readable images, in either the .tif or .jpg format, into drawings for use as backgrounds for tracing, or for applied material textures in 3D models.

Before inserting an image, create and set as current a new layer for images, to preserve the ability to control the image’s visibility separately from other objects in the drawing.

Use the IMAGEATTACH command to bring a Photoshop-readable image into an AutoCAD drawing. In the resulting Image dialog box, specify an insertion point, scale, and rotation, or set these to specify on-screen. Because the image can be moved, scaled, and rotated at any time after being inserted, the entries in the Image dialog box are inconsequential to long-term work.

The DRAWORDER commands prevents images from obscuring other objects in the drawing. However, because AutoCAD rearranges objects following certain commands, it may be necessary to manually reorganize objects repeatedly.

SCALING AN IMAGE: Use the SCALE command to scale an imported image (such as a map or an elevation-oblique image) to its true scale.

1. Type SCALE. When prompted to select objects, select the photograph by clicking on its edge.

2. When prompted to specify a base point, click on any point in the AutoCAD drawing.

3. When prompted to specify a scale factor or [Reference], type R for Reference.

4. When prompted to specify a reference length, click on two points in the image, the distance between which you know.

5. When prompted to specify a new length, type the desired (i. e. the known) length.

 

scale_reference

CLIPPING AN IMAGE: Use the IMAGECLIP command to clip an image to a rectangle or other polygonal frame.

by mikechristenson

Scale Factor

Scale factor is a means of expressing the relationship between a measured object and its representation, or sometimes between a digital drawing and a printout.

Determine the scale factor for common architectural scales by expressing the scale designation as a ratio in the form of 1 : x, as shown here:

232-autocad-guide-04-38

 

Be aware of the visual meaning of scale factor:

ruler

by mikechristenson

AutoCAD: Object Snaps

Object snaps are used to create precise drawings. Use the [F3] key to turn the automatic object snap function on and off. When it’s on, this function automatically “locks” the drawing commands to predefined points (like endpoints and intersections of existing lines).

Type OSNAP at the command prompt to specify the points to which AutoCAD will automatically lock.

Even if the automatic object snap function is off, you can still force AutoCAD to temporarily lock to a specific point in the middle of a drawing command. While drawing, when you’re prompted to specify a point, type the first three letters of the desired snap function (e. g. END for endpoint, MID for midpoint, PER for perpendicular, etc.).

osnaps_01

Note: The NODe object snap locks to points. Points are zero-dimensional AutoCAD objects, the appearance of which is controlled using DDPTYPE. Use the DIVIDE command to automatically draw points at a whole number of equally-spaced divisions along a line, circle, or arc; use the MEASURE command to automatically draw points at predetermined equal intervals (e. g. every inch) along a line; lock to these points with the NODe snap.

 

TRACKING. The object snap tracking function ([F11]) extends the functionality of the basic object snaps. The tracking function “sees” distant points as you’re drawing. When it’s on, and while you’re drawing, move the mouse (without clicking) over a point, and then move the mouse away. The [F3] key must also be “on” in order for [F11] to work.

 

SCREEN CONTROLS. Related: Instead of clicking [F3], you can click the OSNAP button at the bottom edge of the screen. Instead of clicking [F11], you can click the OTRACK button.

by mikechristenson

AutoCAD: Saving and Opening Drawings

SAVING AUTOCAD DRAWINGS:

To save your work, choose [Application Menu] > Save. Always keep at least one fully updated backup copy of your work in a safe place (e. g. one copy on a flash drive and another copy stored online).

 

OPENING AUTOCAD DRAWINGS:

To open a saved drawing, choose [Application Menu] > Open.

 

DIFFERENT EDITIONS OF AUTOCAD:

If you intend to work between two different editions of AutoCAD (for example, edition 2015 at school and edition 2007 on Granny’s laptop), remember that the older edition of the software cannot read drawings produced by the newer edition unless the drawings are deliberately saved in a compatible format. To do this, choose [Application Menu] > Save As in any edition of AutoCAD; choose the appropriate format from the available list.

by mikechristenson

AutoCAD: Special Keys

In AutoCAD, the [Enter] key and the space bar, for most purposes, are identical in function. (For example, typing LINE followed by Enter is equivalent to typing L followed by the space bar.)

Typing the space bar at the Command prompt after a command is completed will repeat the last command typed.

Click the [esc] (escape) key two or three times in succession will cancel any command and return to the Command prompt.

Each of the function keys has a special function in AutoCAD.

by mikechristenson

Linetypes

CONVENTIONAL USES FOR LINETYPES:

Dashed lines are often used to indicate items above the plan cut or in front of the section cut, or objects below or beyond a visible surface.

A “center” linetype (a repeated pattern of single long dash and single short dash) is usually used to indicate gridlines or center lines of objects or spaces.

Specialty linetypes are often used by various engineering disciplines to indicate utility routes; such linetypes often consist of a dashed or broken line annotated with the service description.

by mikechristenson

Lineweights

Lineweight is the visual thickness of lines. The use of lineweight is critically important to maintaining good legibility and professional appearance in drawings.

The following pair of drawings of the Robie House in Chicago illustrate conventional uses of lineweights:

 

 

robie-plan

 

LINEWEIGHT CONVENTIONS:

Discerning objects cut by a plane. Relatively heavy lineweights (e. g. in excess of 0.5 mm) are usually used to designate objects cut by a plane. For example, in a plan drawing, a lineweight of 0.5 mm might designate walls and columns; in a section drawing, the same lineweight might designate floors, walls, and the ground.

Discerning changes in observable planes. Relatively medium lineweights (e. g. 0.3 mm or so) are usually used to designate objects observed against a background. For example, in a plan drawing, a lineweight of 0.3 mm might designate a countertop, an item of furniture, stairs, a balcony edge, and so on; in a section or elevation drawing, the same lineweight might designate the outline or edge of a wall against a distant wall, or an opening in a wall. In an axonometric drawing (such as the one of the Robie House to the left), a medium or heavy line might outline solid objects against a background.

Discerning changes in material occurring on a single plane. Relatively thin lineweights (e. g. less than .1 mm) are usually used to designate changes in material occurring on a single plane. For example, in a plan drawing, a lineweight of less than 0.1 mm might designate a threshold at a door, or the spring point of a ramp; in a section or elevation drawing, the same lineweight might designate trim around a door or window.

Designating material or texture. The thinnest possible lineweight (0 mm) is often, though not exclusively, used for hatch patterns in plans, sections, and elevations. Note that 0 mm does not indicate “no line”; rather, it indicates the thinnest line producible by the selected output device.

by mikechristenson

AutoCAD: Linetypes

Like lineweight, linetype is a property assigned to layers, and by extension, to objects assigned to those layers. Although it’s considered good practice to use layers to organize object linetype, object lineweight is often set on a per-object basis.

LINETYPE SCALE IN AUTOCAD.

All AutoCAD linetypes, with the exception of the default CONTINUOUS linetype, are subject to the LTSCALE system variable. As a general rule, if LTSCALE is increased, the size of the pattern (e. g. the dashes in the line) will increase. However, each different LINETYPE bears a different relationship to LTSCALE. For example, if you set LTSCALE to 1, the DASHED linetype looks like this:
linetype-dashed
Meanwhile, the HIDDEN linetype looks like this:
linetype-hidden
A good rule of thumb for LTSCALE is as follows. Consider the scale at which you’ll print the drawing. Convert this scale to a ratio (e. g. 1/4” = 1’-0” is equivalent to 1 : 48). Set LTSCALE to the right half of this ratio (in this example, to 48). This rule works because if you print your drawing at a comparatively small size, the dashes in the lines should be large relative to the size of objects in the drawing.

TO LOAD A LINETYPE INTO A DRAWING:

1.     Type LINETYPE.

2.     In the resulting Linetype Manager dialog box, click Load.

3.     Choose the linetype you want to load and click OK.

4.     Click OK again to close the dialog box. The linetype is now available to be assigned to layers and/or objects (see below).

 

TO CHANGE LINETYPE ON A PER-OBJECT BASIS:

1.     Load a linetype into your drawing. (See above.)

2.     From the View tab, Palettes panel, click Properties to display the Properties palette.

3.     Click on an object, or a group of objects. Click next to the word “Linetype” in the Properties palette and select a new linetype from the pulldown menu. Click the escape key to deselect the object(s).