Month / November 2014

by mikechristenson

Step-by-Step: Image Trace in Illustrator

Illustrator’s Object > Image Trace commands are used to automatically trace a raster image, creating vector geometry. These commands are especially useful as a step in constructing digital contour models from scanned topographical maps, and other similar tasks.

AN IMAGE TRACE WORKFLOW:

1.  Open a raster image (e. g., a scan or a photograph) in Photoshop.

2.  Using Photoshop, convert the image to a bitmap figure-ground. You will probably need to experiment with the right combination of options to achieve good results. Try using Photoshop’s Filter > Gaussian Blur command to blur the image before converting it to a bitmap (Image > Mode > Bitmap). When converting the image, the 50% Threshold option will usually give the best results. After converting it, change the image mode to Grayscale, and try blurring it again. (The right combination of commands will depend on the resolution and composition of the image.) Save the bitmap image as a TIF file.

3.  Open or Place the image in Illustrator.

4. Use the Selection tool (the arrow tool) to select the image.

5.  Choose Window > Image Trace. This brings up the Image Trace options panel.

6. In the Image Trace options panel, set the Preset to Line Art.

7. Experiment with other settings (including the Advanced settings) to achieve optimal results, depending again on the resolution and composition of your original image.

8. After completing the trace, click on the resulting object and choose Object > Image Trace > Expand.

9. Copy the resulting object into a new Illustrator file. You can also save it as a .DWG or .DXF file, which you can open, import, or link to Rhino, AutoCAD, SketchUp, or Revit.

by mikechristenson

Illustrator: Artboards

Every Illustrator document contains one or more rectangular Artboards (up to a maximum of 100 per document). An Illustrator artboard is analogous to a rectangular piece of paper on which artwork is drawn or pasted. It is similar to an AutoCAD Layout space.

STARTING A NEW FILE.

Whenever you use File > New to start a new Illustrator file, you are prompted to select the number of artboards. By default, the value is 1 (one) artboard, but a single Illustrator file can have up to 100 unique artboards. Entering any number greater than 1 will cause Illustrator to prompt you to select a numbering/display order for the artboards.

EDITING ARTBOARDS.

While working on an Illustrator file, you may need to edit (or add or delete) artboards. This can be done at any time by choosing File > Document Setup and clicking on the Edit Artboards button. The resulting interface includes an options bar (top of the screen) with several customizing options as detailed below. (Note that in the case of multiple artboards, each artboard can have unique settings such as size and orientation.)
The Presets box allows you to select from several standard, predefined artboard sizes. (Artboard sizes can also be customized by dragging handles or by entering custom values for the Width and Height settings.)

The Orientation toggle allows you to select the orientation (portrait or landscape) of the selected artboard.

The Name box allows you to specify a unique name for the selected artboard.

The Move/Copy Artwork with Artboard toggle is either on or off, and controls whether Illustrator objects move if the artboard is moved.

Clicking and dragging within the interface creates a new artboard.

Clicking within an artboard selects the artboard.

Clicking the selection tool (the arrow tool) closes the artboard editing interface, saving your changes, and returns you to the basic Illustrator interface.

TO PASTE ARTWORK ON MULTIPLE ARTBOARDS:

1. Select and copy the artwork you wish to paste.

2. Choose Edit > Paste on All Artboards.

by mikechristenson

Photoshop: Selection

Photoshop allows you to define areas upon which you will apply a tool or command. The act of defining such an area is called selection. The simplest selection tool is the marquee, or rectangular selection tool.

USING THE MARQUEE SELECTION TOOL:

1.  Select the Rectangular Marquee Tool (upper-left-hand corner of the tools palette).

2.  Drag the mouse within the image to draw a rectangular area.

3.  Apply one of the Image > Adjust tools (such as Image > Adjust > Color Balance) to see its effect.

4.  Choose Select > None to clear the selection boundary.

THE LASSO TOOLS:

The lasso tool makes freely curved selections and the polygonal lasso makes polygonal selections.

THE MAGIC WAND TOOL:

The magic wand tool selects adjacent pixels with similar levels of brightness. In the options palette (along the top of the screen), you can set the tolerance of the wand, from 0 (highly discriminating) to 255 (does not discriminate between different values).

Using the magic wand tool:

1.  Choose the magic wand tool from the toolbar. In the options palette, set the tolerance to 30 or 40.

2.  Click within an area of solid color in your image.

3.  Apply one of the Image > Adjust tools to see its effect.

4.  Choose Deselect from the Select menu and then repeat the above steps with different values for tolerance.

SELECTION TOOLS UNDER THE SELECT MENU:

Select > All  selects the entire image.

Select > Deselect  deselects everything.

Select > Reselect reselects the last selection.

Select > Inverse selects any deselected areas while unselecting any selected areas.

Select > Color Range produces similar results as the Magic Wand followed by Select > Similar, although Color Range gives a greater degree of control.

Select > Modify > Border selects a border of specified width along the current selection boundary.

Select > Modify > Feather makes the selection edges soft rather than sharp.

Select > Grow enlarges any selection(s) to include adjacent areas with similar colors.

Select > Similar selects pixels similar in brightness to the currently selected pixels.

Select > Transform Selection allows you to stretch, distort, or rotate a selection boundary.

MOVING AND COPYING SELECTIONS.

Use the Move tool (upper right-hand corner of the Tools palette) to move or copy selected areas. To move selected pixels, choose the move tool and drag the selection with the mouse. To copy, hold Alt while dragging the selection. Hold the Shift key down to constrain the movement of the mouse to horizontal, vertical, or 45 degree motion.

DISTORTING SELECTIONS.

Options under Edit > Transform are useful for scaling, rotating, or otherwise transforming selected pixels. To accept a transformation, press Enter.

To distort a rectangular selection:

1. Use the marquee tool to select a rectangular area.

2. Choose Edit > Transform > Distort. You will see “handles” appear at the corners and sides of the selected area.

3. Use the mouse to move one or more of the corner handles. The selected area will distort to the modified boundary. Press Enter to complete the action.

SAVING SELECTIONS.

Once a selection is defined, it can be saved for later use. (Note that what is being saved is not the content of the selected area, but the shape and quality of the selection border.)

Selections are saved in Channels. Channels are simply grayscale images that correspond to the overall shape of your Photoshop image. The level of gray in a channel corresponds to the “amount” of selection – completely black areas are 100% unselected, and completely white areas are 100% selected.

by mikechristenson

Photoshop: Layers

Photoshop images can be composed of more than one layer. Layers are like sheets of transparent film on which pixels are painted. Layers may be edited separately and individual layers can be made visible or invisible. Layers can be rearranged; their opacity may be changed; their blending mode can be altered, providing different overlay effects. Be aware that each new layer adds a significant amount of information to your file size.

Once selected, a group of pixels can be copied and pasted within its original image or into a new one. The act of pasting creates a new layer (see Windows > Layers).

A multi-layered image can be flattened to save file space and reduce printing time, but the flattened layers cannot be separated. For this reason, it’s good practice to choose File > Save As before flattening layers in a Photoshop image.

LAYERS PALETTE BASICS:

Make a layer current by clicking its name in the Layers palette. Any actions you perform will (in general) affect only the current layer.

Click on the eye symbol in the Layers palette to make a layer invisible or visible.

Change the opacity of the current layer by sliding the bar at the top of the palette. (Note: you cannot change the opacity of the Background layer.)

Change the display order of layers by dragging them up and down on the list.

LAYER BLENDING MODES:

Normal assumes that the top layer is opaque, unless adjusted by some other means (e. g., the Opacity setting in the Layers palette).

Multiply treats white pixels in the top layer as transparent. 50% white pixels are treated as 50% transparent, and so on.

Screen is exactly the opposite of Multiply. Black pixels in the top layer are treated as transparent.

Overlay combines the effects of Multiply and Screen. 50% (gray) pixels in the top layer are treated as completely transparent. Dark pixels become darker and light pixels become lighter.

LAYER ACTIONS:

To add a new layer: In the Layers palette, choose Layer > New Layer and give it a name. By default, new layers are totally transparent in Photoshop until you paste something onto them or paint on them.

To combine layers: In the Layers palette, choose Layer > Merge Visible to combine the visible layers onto the current layer.

To make the entire image into a single layer: In the Layers palette, choose Layer > Flatten Image.

COPYING BETWEEN LAYERS:

1.  Activate the layer you want to copy from and make the selection. Choose Edit > Copy.

2.  Activate the layer onto which you want to paste the selection. Choose Edit > Paste. Photoshop will automatically create a new layer above the current layer.

3.  (Optional.) Click on the new layer in the Layers palette and choose Layer > Merge Down. (This combines the new layer with the layer immediately below.).

 

 

by mikechristenson

Photoshop: Image Resolution

Every Photoshop image is rectangular in shape, corresponding to a fixed measurable size (in inches), and exists at a fixed resolution (usually expressed in pixels per inch).

72 pixels per inch is appropriate for on-screen display (e. g., websites).

300 pixels per inch is appropriate for printed photographs.

600 pixels per inch is appropriate for printed vector drawings and/or text.

Image resolutions greater than 600 pixels per inch might arise in the case of scanned slides.

Use Photoshop’s Image > Image Size command to change an image’s measured size and resolution.

by mikechristenson

What is Photoshop?

Photoshop is an image-editing program – its images are composed of a grid of pixels and closely approximate continuous-tone photographs. Photoshop provides tools and commands used to edit images on a pixel-by-pixel basis.

In general, most operations in Photoshop are of the following form:

1.  Use a tool or a command to select pixels within the image.

2.  Perform an action on the selected pixels to change their color.

by mikechristenson

Step-by-Step: 2D Projections in Rhino

Rhino models can be “projected” into 2D line drawings for use in presentations or construction documentation.

A 2D PROJECTION WORKFLOW:

1.  Open a Rhino model.

2.  Set the view you wish to project (e. g., a perspective view or an orthogonal projection like a plan or elevation).

3.  Enable a clipping plane if required. (See information on CLIPPINGPLANE.)

4.  Type MAKE2D [Enter].

5.  Select the objects you wish to project. Press [Enter] when done.

6.  In the 2-D Drawing Options dialog box, select Current View. Choose other options as appropriate for your situation. (For example, if you check Maintain Source Layers, the resulting 2D drawing will be organized according to the same layering scheme as your Rhino model.)

7.  Click OK.

8.  Although you may or may not see the result of the MAKE2D command on your screen, Rhino has created new objects representing a 2D vector projection of the objects you selected above. Before doing anything else, immediately choose File > Export Selected.

9.  Select the .dwg file format and save the drawing.

10.  After the drawing is saved, immediately click Delete. (This erases the projected geometry in Rhino and allows you to proceed with modeling.)

11.  The resulting .dwg file can be opened in AutoCAD and checked for scale, layers, etc. It can be dimensioned and saved in AutoCAD and/or opened in Illustrator for further editing and annotation.

by mikechristenson

Step-by-Step: 2D AutoCAD to Rhino

Two step-by-step methods for moving from 2D AutoCAD drawings to Rhino:

IMPORT/EXTRUDE METHOD:

This method begins with a set of pre-drawn AutoCAD plans, although the plans could also be drawn directly in Rhino using 2D drawing commands.

1.  Import the AutoCAD drawings to Rhino. [Type IMPORT.]

2.  Create a new layer for the plan drawings. Group the imported drawings into this new layer. [Type LAYER; create a new layer; select objects; type CHANGELAYER.]

3.  Create another new layer for new walls.

4.  Make sure OSNAP is turned on (toolbar at the bottom of the screen). Check END to lock to endpoints.

5.  Invoke the POLYLINE command to trace the wall surfaces from the AutoCAD drawings. (Alternatively, create the wall surfaces as polylines in AutoCAD prior to import.)

6.  Invoke the EXTRUDECRV (“Extrude Curve”) command to extrude the walls to their proper height.

7.  Invoke the CAP command to close the top and bottom of the extruded walls.

8.  Use the BOOLEANDIFFERENCE command to “subtract” openings from the walls.

IMPORT/CONSTRUCT METHOD:

This method begins with a set of pre-drawn AutoCAD plans, although the plans could also be drawn directly in Rhino using 2D drawing commands.

1.  Import the AutoCAD drawings to Rhino. [Type IMPORT.]

2.  Create a new layer for the plan drawings. Group the imported drawings into this new layer. [Type LAYER; create a new layer; select objects; type CHANGELAYER.]

3.  Create another new layer for new walls.

4.  Make sure OSNAP is turned on (toolbar at the bottom of the screen). Check END to lock to endpoints.

5.  Use the BOX command to construct boxes of correct height and size on the AutoCAD drawings.

6.  Use the BOOLEANUNION command to join separate walls together.

7.  Use the BOOLEANDIFFERENCE command to “subtract” openings from the walls.