Autodesk Impression

It's not very often that I get the opportunity to review a brand new product, so it's always a special occasion when I do. The first version of Autodesk Impression has just been released, after being in a "technology preview" stage on Autodesk Labs for almost a year now. Initially code-named Vespa, Autodesk Impression is an illustration tool that lets you create presentation drawings by applying artistic effects to a plain 2D drawing generated from AutoCAD or other design applications. I have to admit that my initial reaction to the sneak peaks of the product given at Autodesk University in December 2005, and subsequently at the AIA 2006 National Convention, was that of being somewhat under-whelmed. After all, Google SketchUp had already announced a similar capability in the form of their Grizzly tool, which has subsequently been integrated into the main SketchUp application as LayOut (see my recent review of SketchUp 6). Also, Piranesi has been around for quite a while, which not only lets you apply sophisticated rendering effects to drawings but also understands depth and perspective of 3D scenes (see my review of Piranesi 4.0). Then, of course, there's the quintessential imaging tool, Photoshop, which is ubiquitous when it comes to image editing and compositing in architectural firms—it also includes a wide array of filters for applying different kinds of artistic effects to an image.

Thus, while Autodesk Impression seemed to be a very useful application for those who want to generate artistic renderings from their AutoCAD drawings, it didn't seem particularly original. But as they say, the devil is in the details, and a closer look at Autodesk Impression revealed that there is a lot more to it than what meets the eye in a quick demo. This review starts off by exploring the basic functionality of the application, and then moves on to look at its more advanced capabilities.

The Basics of Using Autodesk Impression

The starting point for working in Impression is a drawing containing the CAD geometry captured in either a 2D DWG or DWF file. These file types can be directly opened in Impression. Alternately, you can start a drawing from scratch using an Impression template and then import DWG or DWF content into it. In the case of a DWG file, Impression gives you the choice of opening or importing the model space, any of the layouts, or even just a specific viewport within a layout. Figure 1-a shows a layout drawing in AutoCAD, which is subsequently being opened into Impression for the purpose of illustrating it. The layout in AutoCAD was a copy specifically prepared for use in Impression, in which all unneeded layers such as those containing text and dimensions were turned off. There are several additional guidelines recommended for preparing AutoCAD files to get the best results in Impression, which will be discussed in detail later. As you can see from the Open dialog for Impression shown in Figure 1-b, if the source DWG file uses a plot style, you can retain those color, lineweight and linetype settings in Impression. You can also set a stroke type to instantly create a consistent, hand-drawn look for all the incoming geometry. The Open dialog has an option to change the measurement unit, as well as some additional options that can be seen by expanding the dialog using the Arrow button on the bottom right corner. These relate to the more advanced features of Impression which will be discussed in the next section.

The AutoCAD layout now appears in Impression as shown in Figure 2, with the stroke style selected in the Open dialog. As you can see, the interface of Impression is clean and uncluttered, with the bulk of the screen real estate devoted to the canvas where the drawing is displayed. The three main palettes of the application, Layers, Style Editing, and Styles, are contained in a single dashboard, which is positioned on the right of the window in Figure 2. There is an optimal set of geometry, text creation, and some additional tools which are concisely captured in a single toolbar running at the top of the window. Most of the settings and options associated with the different tools and palettes can be seen and accessed in flyout panes that are opened when you move the cursor over the white flyout arrows (some of these are visible in Figure 2) instead of in separate dialogs. This makes the application very easy to learn and navigate.

Every Impression drawing has an organizational hierarchy made up of sketches, layers, and objects. When a drawing is opened that was created in an application such as AutoCAD, each viewport in the layout is converted to a separate Impression sketch with its own set of layers, even if those viewports shared the same geometric model and the same layer structure. Thus, as shown in the Layers Palette in Figure 2, the four viewports have become four sketches with distinct sets of geometric objects and distinct sets of layers. The Layers palette works a similar way as in other CAD programs, with options to make a layer current, turn its visibility on or off, and lock or unlock it for editing. You can also associate a display style with a layer which will be applied to all the objects on it. Layers also determine the draw order of the objects contained in them, and they can be re-positioned as required by dragging them around in the palette. You can create layer groups as an organizational unit for grouping layers based on draw order and related appearance styles. A quick preview of all the objects in a layer, layer group, or sketch can be obtained by moving the cursor to the corresponding flyout arrow in the Layers palette.

The next step is to start illustrating the drawing using the wide variety of styles that are provided with the application. This can be done in three ways, all of which are illustrated in Figure 3. You can select one or more objects and apply the desired style directly to them by double-clicking on it in the Styles palette. This works well for line objects or for filled objects that have been created as closed polygons, such as the window panes shown in Figure 3-a. For those parts of the drawing that have not been created as filled polygons, the object-selection method will not work. An alternate Area Fill tool is available, which can be used to fill an enclosed area with the selected style, such as the wall expanse shown in Figure 3-b. The third method is to apply a style directly to a layer by dragging and dropping it from the Styles palette to the Layers palette. All the objects on that layer will now be displayed in that particular style. However, this works well only if objects have been properly organized into layers for the purpose of being illustrated in Impression, and I found this to be true only of the sample files that came with the application. For regular AutoCAD files, even those created with the correct layering standards for CAD tasks, the layering will not be suitable for using the layer method of style application in Impression, as shown in Figure 3-c. This is unfortunate, because if layers are used to stylize the illustration, those settings can be captured in a Style Map which can then be applied to other drawings with the same layers to instantly stylize them with the same display settings. We will get back to looking at style mapping in more detail later.

Let's look at styles in a little more detail, as they are the essence of Impression. The application ships with several libraries containing a wide array of styles, ranging from line strokes that look like pencil work, fills that resemble markers and watercolors, texture maps, gradients, and so on (see Figure 4-a). Each style in turn is made up of one or more style elements, whose parameters can be seen and edited in the Styles Editor palette to fine-tune the exact look and feel of a particular style (Figure 4-b shows some of the settings for the style used on the wall in Figure 3-b). You can also add more style elements such as strokes, hatches, outlines strokes, effects such as drop shadows, and so on to an existing style, set the parameters of the new elements to desired values, and save that as a new style if required. Figure 4-c shows a new Stroked Fill style element added to the style from Figure 4-b and the resulting change in the appearance of the wall to which that style was applied. You can also start with a clean slate and create a brand new style from scratch, adding all the style elements you need set to the desired parameters. The number of style elements and the vast range of their individual settings makes it possible to create an almost infinite variety of styles in Impression, which can be saved in files that can shared with other users and re-used in other drawings. Thus, individual users as well as firms can create their own signature styles and apply them across all the drawings in a specific project or across all their projects for a trademark look and feel to their presentation drawings.

In addition to stylizing the geometry that was imported from the CAD file, you can also embellish the drawing by creating additional graphics and annotation objects within Impression using the drawing and text tools. You can also add entourage elements such as trees, people, cars, skies, and so on from the set of block libraries that ship with the application. The scale of these blocks can be adjusted so that they can be used in drawings of all scales. All this additional content could be created on new layers to separate them from the original drawing content. Once the illustration is finished, it can be saved in a variety of standard formats such as BMP, JPEG, DWF, EPS, PDF, and PNG, in addition to IRF, the native file format for Impression (IRF stands for Impression Rendering Format). The Impression file can also be saved with its layers intact in Photoshop's PSD format, so you could subsequently open it in Photoshop for further refinement of the individual layers if necessary. For printed copies of the illustration, you could print directly from Impression or using any of the above-mentioned formats that have high print fidelity.

Advanced Capabilities

Let's look more closely at the style mapping capability that was mentioned in the last section. If the drawing has been prepared in the authoring CAD application in such a way that objects of the same type that need to be rendered in the same way are created on the same layer, the best way to stylize it is by applying styles to the layers rather than to the individual objects or by using the Area Fill tool. This is because all the layer-to-style mappings are captured in a style map, which is saved along with the file. If you now open another drawing that has the same layer structure, you can use the Import Style Map command to apply the style map of the saved Impression file to the new file. All its layers will get immediately associated with the same styles and the entire drawing will be displayed with the same settings as the saved file, with no additional investment of time and effort. Figure 5-a shows a completed Impression rendering for an elevation drawing in which all styles were mapped by layers, and the subsequent import of its style map to instantly render another elevation drawing that has the same layer structure, shown in Figure 5-b. In order to be able to use style mapping in Impression in this manner, properties such as color and lineweight should be assigned by layer instead of by object in AutoCAD. Also, hatching should be avoided to simplify the drawing as much as possible.

Another very useful and time-saving feature in Impression is block substitution. Not only can you add blocks to embellish a drawing in Impression, you can go a step further and replace all the instances of an existing block (such as the foliage blocks created in AutoCAD shown in Figure 6-a) with a new one in a single step. All that you need to do is drag the desired block from the Blocks palette and drop it on top of the old block in the drawing. The application automatically detects that you are trying to replace a block and opens up a dialog where you can fine-tune the substitution settings (see Figure 6-b). All instances of the old block in the drawing will now get replaced by the new block. You can set the scale and rotation of the blocks to vary by a selected value, which is very useful when displaying trees or foliage, for example. You can even group a number of blocks into a "multiblock" and use that for the substitution—it will replace the old set of blocks randomly with different instances of the new blocks, as shown in Figure 6-c, which has four different types of foliage blocks grouped into a multiblock. Just as with styles, you can create and save block substitution maps that can be used to speed up the block substitution process in many drawings of the same type. You can also create new blocks from any selected objects and save them in libraries to be used across projects.

Any rendering that is created in Impression from a DWG file can be updated if the geometry in the original file is modified. You can choose to update the entire file or only specific sketches or layers. This capability is very handy as it allows users to develop presentation drawings even while the design is being developed, without having to start over as you would have to do if you were creating presentation drawings manually or using another illustration tool.

Additional features of the application include the ability to automatically remove hidden lines when 3D views are being imported, and the ability to import hatches, clipped objects, and wide polylines from the CAD file. Also noteworthy is the fact that all the objects created in Impression are vector-based and can be easily modified using grips.

Strengths and Limitations

Autodesk Impression is a visually pleasing, fun, and easy to use application. I found that the overall style of its interface—the fluidity, simplicity, intuitiveness, and general look and feel—was very reminiscent of Autodesk Architectural Studio, Autodesk's well regarded conceptual design product that it was unfortunately forced to discontinue in 2004 (see AECbytes Newsletter #13). It is possible to get into Impression and convert a drab-looking computer drawing into a decent-looking presentation drawing in less than an hour, even for those who are not particularly artistic. And in the hands of professional illustrators, Autodesk Impression can become a powerful tool for creating beautiful-looking renderings a lot more quickly and efficiently than by hand-drawing or by using another imaging tool. Its power lies in the fact that it is specifically designed for creating illustrations from CAD drawings as opposed to being a general image-compositing tool. The near-infinite variety of styles that can be created and applied to drawings provides users with ample scope to design their own very unique signature styles that look very different from those created by other users. Advanced capabilities such as style mapping and block substitution can lead to much faster turnaround of presentations drawings for a project, and the ability to update the drawing with any changes made to the CAD geometry ensures that the time spent on developing the presentation drawing is not wasted even if the design is changed. And the best part is that these advanced capabilities are not "in your face," so to say, and do not overwhelm the user in the initial stages of getting familiar with the application. They can be explored and used once a comfort level with the basic illustration features of the application has been achieved.

Autodesk Impression is well supported by plenty of learning resources, both included with the application as well as online, making this easy-to-use application even easier to learn. For the first few times, the application launches with a Quickstart Tour that walks you through three basic steps of the application—applying a style to a layer, using the Area Fill style to apply a style directly to areas in the drawing, and substituting an Impression block for an existing one—with the use of three different sample files. There is also a Quick Start Guide that provides a more in-depth introduction to the application using a series of animated demos and feature overviews. Both of these are in addition to regular Help system that provides detailed information on each tool and process. Additional tutorials are available in the form of videos on the Autodesk Impression website. There is also an Impression Community website which functions as an overall resource hub for Impression users.

I found that the biggest limitation of Autodesk Impression was with respect to its style mapping capability, which was technically a great feature but not very useful in practice, as drawings are rarely generated in the layering style needed for this to work. This is true even when AutoCAD is used to create the original CAD file. When it comes to other applications like Revit that do not work with the layers concept to begin with, the usefulness of style mapping is even more limited. You could export a Revit sheet to DWG format, which does some mapping of Revit objects to layers, but the mapping doesn't work well enough to be used for style mapping in Impression (see Figure 7).

I also found that the process Impression follows of breaking up the different viewports in a layout drawing into different sketches with their independent layers goes against the potential benefits of style mapping. Assuming that the original AutoCAD drawing had layers properly set up for style mapping in Impression, you would not be able to map styles to layers for all of the viewports at once. Since each viewport is now a separate sketch, you would have to go through the style mapping exercise for each viewport separately, even if you wanted all of them to have a uniform look, as in the case of the sheet with the four elevation drawings shown earlier in Figure 2.

While Autodesk Impression works wonderfully for illustrating 2D views, it lags far behind Piranesi's technology for the rendering of 3D views, which understands perspective and depth and can therefore automatically adjust the size of a texture applied to a surface according to its depth. Thus, for instance, if a brick texture is applied to a wall in a perspective view in Piranesi, the tile sizes will automatically recede along the vanishing point of the view. Even entourage elements, placed as cutouts, are automatically sized to scale depending upon the scale of the model and the position of the cutout, so that the further away you move the cutout from the eye position in the scene, the smaller it gets. Also, the new version of Photoshop scheduled to be released this month has been enhanced with 3D capabilities (look out for its upcoming review in AECbytes). Autodesk Impression does need to rethink how it works with 3D views, which are currently illustrated in the same way as 2D views.

Given the competitive landscape in which it plays, comparisons of Impression with SketchUp's LayOut capability are also inevitable. While both products seemed somewhat similar in earlier demos such as those given at last year's AIA Convention, I found that the two products were actually quite different after getting the opportunity to work closely with both of them. Recall from my recent review of SketchUp 6 that LayOut is, first and foremost, a page layout utility for SketchUp models, making it more like AutoCAD's Layout tabs or Revit's Sheet functionality. It works only with SketchUp models and is not intended to be a general illustration tool like Impression. LayOut is also totally lacking the ability to create and apply new presentation styles and has to rely on the styles that have been created in SketchUp's modeling environment to display the images in a specific way. On the other hand, styles are the "bread and butter" of Impression, so to say—it couldn't operate without them.

Conclusions

Given the usefulness of Autodesk Impression in creating the kinds of 2D illustrations that were the mainstay of architectural practice for so many years, it seems a real pity that Autodesk Impression wasn't developed 10 or even 5 years earlier when 2D drafting was still the norm. It would have been a runaway success by making life much easier for so many architects—including myself!—who had to painstakingly generate artistic looking images from the sterile-looking output of their CAD programs. Ironically, Autodesk Impression is being introduced at a time when an increasing number of architectural presentations are featuring highly photorealistic renderings of 3D views and animated walkthroughs of 3D models. Despite this, Impression would still be compelling if it could integrate with Revit and other BIM applications as well as it works with output from AutoCAD, along with overcoming the style mapping limitations described in the last section. Having an understanding of perspective and depth like Piranesi would also be useful, given the increasing focus of design presentations on 3D views rather than on 2D plans, elevations, and sections. Let's hope future releases of Autodesk Impression address these issues and imbue this otherwise delightful new tool with sufficient staying power in the AEC industry.

About the Author

Lachmi Khemlani is founder and editor of AECbytes. She has a Ph.D. in Architecture from UC Berkeley, specializing in intelligent building modeling, and consults and writes on AEC technology. She can be reached at lachmi@aecbytes.com.