There will be times when you will be rushing to get a rendefing do~e and don’t want to wait for each trial rendering to become visible. AutoCAD offers several tools that can save you time by limiting the resolution or area being rendered.
]Suppose you just want to render the area where you’ve added a tree to make sure
it is in the right location. The following exercise will show you how this is done.
1.Choose View >Named Views, and then restore the 3DFront view.
2 Open the Render dialog box and set the Destination option to Viewport.
3 Click the Crop Window check box to activate this option, and then click the Render button.
4 The prompt Pick Crop Window to Render: appears. Select the area , indicated by the rubber-banding square. Once you select the window, AutoCAD renders only the area you selected.
The Crop Window option is a worktng tool and is not available when File or Render Window are selected as destinations.
You can also select specific objects to be included in the rendering by checking the Query for Selections check box in the Render dialog box. This option asks you to select a set of objects before it proceeds to render. You can render to all three destination options with Query for Selections turned on.
If you want to get a quick rendering with a reduced resolution to check composition, you can use the Sub Sampling drop-down list. Try the following exercise to see how it works.
1. Open the Render dialog box, and then open the Sub Sampling drop-down list.
2. Choose 3:1 from the list, make sure the Crop Window option is unchecked, and then click the Render button. Your view will render faster, but will look a bit crude
The different ratios in the Sub Sampling option tell you how many pixels are being combined to reduce the resolution of the image. For example, 3:1 combines three pixels into one to reduce the resolution to a third of the original.
Smoothing Out the Rough Edges
The Sub Sampling option increases the jagged appearance of your rendering because of the reduced resolution. For your final rendering, you can actuallv improve the smoothness of edges and thereby increase the apparent resolution by using the Anti-Aliasing option in the Render dialog box. This option performs a kind of computer trick that reduces the jagged appearance of object edges. Anti-Aliasing blends the color of two adjacent contrasting colors. This gives the effect of smoothing out the “stairstep” appearance of a computer-generated image. The improvement to your rendering can be striking. Try the following exercise to see firsthand what Anti-
Aliasing can do.
1. Open the Render dialog box, and tlu-n click the More Options button.
2. In the Raytrace Rendering Options dialog box, click the Medium radio button in the Anti-Aliasing button group, and then click OK.
3. Select 1:1 from the Sub Sampling drop-down list, and then click the Render button. The rendering takes several minutes, so you may want to take a break at this point. When the rendering is done, it will look similar.
Notice that the edges of the buildings are much smoother. You can also see that the vertical mullions of the office building are more clearly defined. One negative point is that the texture effect of the Facade model has been reduced. You may have to increase the scale value for the Granite Pebbles material setting to bring the texture back.
As you can see from this exercise, you trade off rendering speed for a cleaner image. You will want to save the higher :Anti-Aliasing settings for your final output.
In this chapter, you’ve participated in a guided tour of AutoCAD’s rendering tools and have seen the main features of this product. Because of space considerations, this chapter didn’t go into the finer details of many of its features) but you now have the basic knowledge from which to build your rendering skills. Without too much effort, you can adapt much of what you’ve learned here to your own projects. If you need more detailed information, use the Help button found in all the Render dialog boxes.
Computer rendering of 3D models is a craft that takes some time to master. Experiment with these rendering tools to see firsthand the types of results you can expect. You might want to try different types of views like an Isometric or Elevation view, the latter.With a bit more detail added, this’ rendered elevation could fit nicely into a set of renderings for a presentation.