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posted 06/27/07 by Todd Hunter All Around the Block

Working with Blocks in Autodesk Impression

Similar to AutoCAD and other CAD programs, Impression uses blocks for objects that need to be repeated, edited globally, and stored in libraries.

Blocks in Impression are also called Entourage because they are usually applied to illustrations as additional scenery to add detail and a sense of scale to the image.

Impression has many parallels with AutoCAD in terminology and workflow and the usage of blocks is very similar in the two tools.

Finding Blocks
Blocks are accessed through the blocks palette. This can be found in the Palettes pull down menu or it can be opened by hitting the F4 function key.



The blocks palette has two viewing modes: the thumbnail mode, and the navigation mode. The thumbnail mode uses the whole palette to show more thumbnail previews of blocks, and the libraries are accessed from a drop-down list a the top. When you toggle the Expand arrow in the lower left corner of the palette, the view turns to the Navigation mode. This splits the palette into a left and right pane, and allows you to navigate the block libraries and search filters more easily on the left and still gives you a smaller thumbnail preview window on the right



There are two areas on the left, the Libraries list and the Search Filter list. In the search filter list we have Saved Blocks and In Use Blocks. This IRF file has no blocks in it yet so the saved blocks and in use filters are blank. In the Libraries list, there is a list of default block libraries that is set up during installation.

These listed libraries are actually externally referenced files that are always available to browse and pull from. These files are really just .IRF files that contain one or more blocks. You can add as many external libraries as you want by navigating to the folder where the IRF is and then selecting the IRF file that contains the blocks you want to have available as a library.

Adding a Block Library
Let’s add a library of pre-made blocks to our library list.
Press the Link to Libraries icon (that looks like a blue folder) in the lower right corner of the blocks palette.
Navigate out to the impression install directory and find the subfolder called libraries\styles\plants.
Notice that there is a list of IRF files. Where applicable, the default library files have a naming convention that denotes whether the block image will appear in the background, midground, or foreground when placed your Impression illustration. There are some file names with either a BG, MG, or FG on the end of the filename (background, midground, & foreground respectively). This simply means that the blocks for the background are low in detail and blocks in the foreground will be higher in detail. You may choose to use a similar naming convention for block libraries that you create.
Select an IRF and preview the blocks in that file on the right.
Select the IRF you want and click the Open File as External Library button to add it to the list of libraries in the blocks palette.

Now you have an addition library to choose from that will remain in the list until you remove it.

Inserting a Block onto the Canvas
To insert a block in to your illustration first make sure the layer you want to insert the block on is current by checking the check to the right of the layer name, then simply select the thumbnail of the desired block and drag it from the palette onto the canvas. When you do that the Block Properties Summery appears. This tells you what size your block will print based on the scale of the current sketch (default canvas). Though you can edit size and scale here, this dialog is mostly informational and you can select to not have it appear every time you insert a block by checking the Don’t show me this again box in the lower left corner. Notice that now you have inserted a block, the block is listed in both the Saved Blocks and In Use Blocks Search Filters in the blocks palette.

Search Filters List
The Saved Blocks filter shows all of the blocks stored in the current IRF file. Remember that you dragged your block in from an externally referenced library. Now that it has been inserted it stays with the IRF file.

The In Use filter lists all of the blocks that are actually on the canvas. If you delete a block from the canvas, it no longer appears in the In Use filter, but it will remain stored in the IRF and listed in the Saved Blocks filter list.

Image

Block Scale and Size?
Although Impression is designed to open CAD files and illustrate them, the accuracy that CAD platforms offer is secondary when placing entourage in your Impression illustration. The size they will be when printed with the image is more of a concern and that is why the Block Properties Summery is mainly informational. However, the accuracy does exist in Impression. The pre-made block libraries that come with impression are created to the generic scale of 1/8” = 1’- 0”.

If you open a CAD layout that is at a scale other than 1/8” = 1’- 0”, when you drag a block onto the canvas, it may appear a little too large or a little too small. You can adjust the size in various ways. The simplest way is to select the block on the canvas and use the grips on the bounding box and drag the block to an appropriate size. You can maintain the aspect ratio of the block by holding the Shift key while dragging a grip. Holding the Shift while dragging will make sure your people entourage won’t get squished while dragging, however, you may want to freely drag planted or natural objects like trees and shrubs without the Shift key in order to make them appear random in size and shape.

There are ways to make entourage look varied, random, and natural but if you desire more accuracy, you can adjust the size and scale of a block with the Properties palette.

You can adjust the properties of an individual block by selecting the block and hitting the F2 key to open the properties palette. Any adjustments made here will affect only the selected block. You can also make an adjustment that will affect all blocks on the canvas that have the same name by going to the Saved Blocks filter and selecting the thumbnail of the block you want to edit. Right-click on it and choose Properties. Any changes made here will affect all blocks of that name.

What Layer is my Block On?
Your block was inserted onto the current layer. The layer of the block can be changed with the properties palette or by right clicking the block and selecting the Send to Layer option.
Creating Custom Blocks
Impression comes with a large library of blocks to get you started. There is also a collection of block content on the Impression community site on the web. If these blocks don’t suit the style of the illustration you are working on or a particular type of block does not exist, you can easily create your own blocks in Impression then store them in libraries to be referenced and used over and over.

Creating Blocks from Impression Geometry
You may choose to use the geometry creation tools in Impression to create your own custom blocks. This way you can use similar styles to the ones you are using to create your illustration. For example, you may be creating an all colored pencil rendering and you want the entourage to also be styled in colored pencil.

Before you create the geometry that will become a block, you should consider the layers and styles you will use. Depending on how you will organize the visibility of your blocks there are a couple of ways to set up layers for block creation. One way is to use no style overrides. This means that for every different part of the block that needs a different style, a different layer is created and a specific style is applied to that layer. For example: You are making a tree block. The tree geometry consists of two parts, the branches and the leaves. For the branches you will use a thick brown pencil stroke style and for the leaves you will use a green stroked fill style. First create two layers, one called Branches and the other called Leaves. Then apply the brown pencil stroke style to the Branches layer and the green fill style to the Leaves layer. As you create the tree geometry, make sure you are on the proper current layer for each element in the block.

After you have created your geometry that you want to make a block from, making a block is quite easy.

Open the Blocks palette
Select all of the geometry for the block
Pick the Create Block From Selection icon at the bottom of the Blocks palette

Your block is created and automatically added to the Saved Blocks filter list. A thumbnail is created and the name field is flashing, prompting you to name it. If you don’t name it at the time of creation, an incremental default name is given to the block. You can rename the block at any time.

The base point of the block is always the center mass of the bounding box around the selected objects.
Redefining Blocks
You can redefine any block by selecting the new geometry or image you want to redefine the block with, and choosing the Redefine Block icon at the bottom of the blocks palette. A Redefine Block dialog will appear with a dropdown list of all of the blocks currently saved in the IRF file. Use the list to select the block you want to redefine. You can also select a new base point for the block. Be aware that if you change the base point when redefining a block, it will cause all blocks with that name to move from their current inserted point.


Creating Blocks from Raster Images
You may have existing libraries of entourage that you have been using with other graphics products that you want to incorporate into Impression libraries. Creating blocks from raster images is as easy as creating block from Impression geometry described above.

Let’s assume you want to create a custom library of blocks from raster files. It is best to start off with a blank canvas. You might want to create descriptive layer or set of layers for your blocks to be created on.

The procedure is thus:

Make sure you are on the desired current layer for the block to be placed on
From the File menu, select Import (or hit Ctrl-I)
Navigate to the raster file you wish to import
Click OK

Your raster image will come into the canvas at whatever pixel resolution it was created with. In most cases it will need to be resized to something more appropriate for the scale of your rendering. You can resize it by holding the Shift key while dragging the grip handles on the bounding box. This will let you give it an approximate, visually correct size. You can also adjust the height and width in scaled inches of the raster image with the Properties dialog by selecting the image and hitting the F2 key. This value in inches is based on the scale of the current sketch or canvas.

Once the image is the proper size, simply select the Make Block From Selection icon in the blocks palette, and give your new block a name.

To continue making a library of raster images, just repeat the procedure. It might be best to organize to images on the canvas in rows and columns for better management, but since this library will be used as an externally referenced library, all that matters is that the blocks exist in the Saved Blocks search filter.

Why PNG?
PNG raster files work best for blocks in Impression because they mask unwanted background color. Below is an example of the steps to take for converting a JPG of a tree and converting to a PNG file with Photoshop.

1. Open the jpeg file in Photoshop (if you are scanning in Photoshop, then you can omit this step and work directly on the unsaved file).
2. Go to “Select” menu and pick “Color Range”.
3. Click in the black preview area (avoid clicking on the tree itself).
4. Adjust the “Fuzziness” value (this value could change for different images, but I guess 50-80 would usually work) till you see most of the tree becomes black.
5. OK and you have just selected the white background.
6. Go to “Select” Menu and pick “Inverse”, now you’ve selected the tree itself (could also include some white back ground if the color range selection is not so perfect).
7. Remove any obvious white background from the selection (by obvious, I mean the background that gets selected pretty away from the tree).
8. Go to “Edit” menu and “Copy”.
9. Start a new file, be sure to set the “background content” to be transparent.
10. Paste the tree.
11. Save as a PNG file.

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