Page 249 - Enhancing CAD Drawings with Photoshop

4386.book Page 233 Monday, November 15, 2004 3:27 PM
RENDERING IN AUTODESK VIZ 233

NOTE See Chapter 1 for a discussion of why RGBA images have 32 bits per pixel.
9. The Targa Image Control dialog box appears. Click the 32 Bits-Per-Pixel radio button. Check
Compress for a smaller file size. Also, check Pre-Multiplied Alpha before clicking OK. Close
the RFW.

WARNING The alpha channel must be premultiplied for efficient compositing in Photoshop;
otherwise, transparency and anti-aliasing around the object boundaries are thrown off.
Congratulations, you have successfully rendered your first compositing image! We will
repeat the object rendering process once more so you get some practice performing these
steps manually.
10. Press Ctrl+Z to undo. This is an essential step in the object-rendering work flow! Undo doesn’t
count for the steps you performed in the RFW; in this case, it undoes the material assignment
from step 6. The objects return to their original materials, and the white triangular corner tabs
that appear in each corner of the Matte/Shadow sample slot disappear, meaning the material
is now cold (or unused in the scene).
11. In the Selection Floater dialog box, click the next object (in this case, Glass Curved). Click
Invert, and then click Select.

12. In the Material Editor dialog box, click Assign Material To Selection.
13. Press Shift+Q to do another quick render.
14. Click Save Bitmap in the RFW. Save the file in the same folder you used in step 8. Type Glass
Curved.tga in the File Name text box and click OK.

WARNING Always use the same filename as object name to avoid confusion.

15. Click OK in the Targa Image Control dialog box to use the same settings as you did in step 9.
16. Close the RFW if it’s in your way, and remember to undo once and only once; press Ctrl+Z to
do this.
At this point you could repeat steps 11 through 16 for each object in the scene. Because this scene
has only nine objects, this wouldn’t take long. Feel free to do this to practice the object-rendering pro-
cess until you understand why you are performing the steps—but the next section will show you why
you don’t have to do all the work.

Automating Output with MAXScript
One of the advantages of using Autodesk VIZ is the potential to use its powerful scripting language
called MAXScript to reduce repetitive tasks. I’d like to give you a script that I’ve written to help with
the more complex scenes you may be creating in your own projects. What if there are a few hundred
objects in your 3D scene? Who would want to manually repeat the object-rendering steps that many
times? In fact, by itself this MAXScript is worth the price of this book when you consider how much
time it can save you.