Eliminating Errant Objects

Fixing Problems in CAD Models

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Autodesk 3ds Max Tutorials > Project Management > Fixing Problems in CAD Models > 

Resolving Other Common CAD Problems

Many companies that use AutoCAD have vast archives of drawings that were originally created many years ago. If you need to work with any of these drawings or models, you can encounter problems in 3ds Max because of the way older AutoCAD settings and objects are now interpreted. Such common problems involve the following:

• Great distances between objects in the CAD drawing and the drawing origin.
• The use of the Thickness setting to display objects that projected into the Z-axis, like extrusions.
• Imported objects are not as smooth as you would like them.
• Unit settings saved with the CAD model need rescaling.
• Texture maps applied to a CAD model, are not found when the model is opened in 3ds Max.

Drawing origin placement:

Large scale drawings can pose problems due to objects being placed at vast distances from the drawing origin.

1. In AutoCAD, open ts_cad_2.dwg or ts_cad_2_r14.dwg, depending on the version of AutoCAD you're running.
2. Choose File menu > Save As and save the file as myImport3.dwg.

   Once again, you're doing this to preserve the original drawing so the tutorial can be easily repeated.

3. Minimize AutoCAD.
4. Open 3ds Max or choose File menu > Reset to reset the scene.
5. Choose File menu > Import and open myImport3.dwg.
6. On the AutoCAD DWG/DXF Import Options dialog, turn on Rescale in the Scale group and set the Incoming File Units to Feet.
7. After you click OK in the AutoCAD DWG/DXF Import Options dialog, a warning indicates a potential problem with the file. Click Yes to proceed. You’ll deal with this in a later step.

   

8. In the Perspective viewport, zoom in to get a better view of the scene. You'll see several objects, but not all of them on the ARWALL layer. These objects have vertical faces with normals pointing in a number of directions.
9. Reset and minimize 3ds Max.
10. Restore AutoCAD and initiate the Move command.
11. Select the entire drawing and when asked to specify a base point, pick a point near the center of the drawing.
12. When asked to specify a second point of displacement, enter the coordinates 0,0,0 and press Enter.

    This moves all the objects to the origin and allows 3ds Max to more accurately determine location data.

13. Perform a Zoom Extents and then save the drawing.
14. Restore 3ds Max and choose File menu > Import.
15. Open myImport3.dwg and make sure to turn on Rescale.
16. Set the Incoming File Units to Feet and click the OK button.

    You have now eliminated the warning message that displays while importing the drawing.

    For more information about the importance of keeping the model close to the scene origin, refer to the System Unit Setup Dialog topic.

Remove line thickness:

While a drawing that contains lines with thickness may give the appearance of a 3D model in AutoCAD, the lines only display a framework. These can sometimes pose problems when imported to 3ds Max so this section demonstrates how to quickly rest them.

1. Continue from the previous section and minimize 3ds Max.
2. Restore AutoCAD and open the Layer Properties Manager and then make ARWALL the current layer while freezing all the others.

   

3. From the menu, choose View > Named Views. In the View dialog, select West, then click Set Current. Click OK.

   The view adjusts to a perspective orientation. Only lines have a Thickness value; therefore only they should be selected so the values can be adjusted at the same time.

4. Use Zoom Extents to see the entire drawing.

   

5. At the AutoCAD command line, type Change, press Enter, then type 'filter to begin the command and open the Object Selection Filters dialog.
6. From the Select Filter drop-down list, choose Line, then click Add To List, then Apply.

   

7. Using a selection window, select all the objects in the scene, then press Enter twice to return to the Change command.

   Only the Line objects, as defined by the Filter command, are selected.

8. Type P (for Properties) then T (for Thickness) and then enter 0 when prompted to specify a new thickness. Press Enter twice.

   

   The lines on ARWALL layer are now uniformly at zero thickness.

9. Save the drawing, then import the file into 3ds Max again.

Adjust smoothness:

There are two ways to deal with smoothness when you import or file link a 3D object to 3ds Max. You can make adjustments to smoothing groups that will give the illusion of smoothness when a model is rendered or you can increase the number of faces and surfaces of an object to get smooth results. This section addresses the two methods of handling smoothness.

1. Reset 3ds Max and choose File menu > Import.
2. Open canopy.dwg from the \tutorials\designviz folder, stopping when the AutoCAD DWG/DXF Import Options dialog opens.
3. Turn on Rescale and set the Incoming File Units to Inches.
4. Make sure Derive AutoCAD Primitives By is set to Layer, Blocks As Node Hierarchy, set Smooth-Angle to 15.0 if necessary, and then click OK.

   

5. Switch to the Perspective viewport to a User viewport by pressing U.
6. Using Zoom Region and Pan, zoom into the central part of the model until you can clearly see the canopy overhanging the main doors.

   You might have to use Zoom Region a couple of times and pan around a little.

7. Choose Rendering menu > Environment and turn off the Active switch in the Exposure Control rollout.

   If left on, the colors in the scene are over saturated and appear to be self-illuminated.

8. On the main toolbar, click Quick Render.

   The cylindrical canopy element is segmented rather than smooth, because the Smooth-angle value was too low during import.

   

9. Press H to open the Select Objects dialog and select the Layer:CanopyEnd object.
   TipUse the search field above the objects list.
10. Delete the Layer:CanopyEnd object.
11. Import the file again. Stop when the AutoCAD DWG/DXF Import Options dialog opens.
12. On the Geometry panel, turn on Rescale, set Incoming File Units to Inches, and make sure Derive AutoCAD Primitives By is still set to Layer, Blocks As Node Hierarchy. Set Smooth-Angle to 60.0 and then click OK.

    

13. Open the Layers panel and activate Select From List.
14. Click the None button, scroll to the bottom of the list and then choose the CanopyEnd layer. Click OK.

    

15. Zoom and Pan to the canopy and render the scene again.

    

    Notice that the object looks much smoother.

16. Right-click the User viewport label and change it to Wireframe.

    

    In this display mode, you can see that the Layer:CanopyEnd object does not have much detail and relies upon smoothing groups to derive its smoothness.

Adjust smoothness with File Link:

This section will basically repeat the previous section but incorporates the File Link Manager and also highlight the Surface Deviation setting for 3D solids. Surface Deviation is very useful when dealing with 3D objects that always seem to have jagged edges when they're imported or linked to 3ds Max.

1. Reset 3ds Max.
2. From the Customize menu, choose Units Setup, and then on the Units Setup dialog choose Generic Units.
3. Choose File menu > File Link Manager.

   Next you'll create a new preset to ensure that File Link uses a Derive By setting that shows the object colors.

4. On the File Link Manager dialog, click the Presets tab.
5. Click the New button; this opens the New Settings Preset dialog. In the New Name field enter Canopy and then click OK.

   The Canopy preset appears in the list.

6. Click the Canopy preset and then click Modify.

   This opens the File Link Settings dialog.

7. Click the Advanced tab and set the Derive AutoCAD Primitives By field to Layers, Blocks as Node Hierarchy. Click Save.

   This returns you to the File Link Manager dialog.

8. Click the File button and open canopy.dwg from the \tutorials\designviz folder.

   The file name and path appear in the File field.

9. From the Preset drop-down list, choose the Canopy preset.
10. Turn on Rescale, set the Incoming File Units to Inches, and then click Attach This File.
11. Switch the Perspective viewport to a User viewport by pressing U.
12. Use Zoom Region and Pan to zoom into the central part of the model so you can see the canopy again.
13. Choose Rendering menu > Environment and make sure the Active switch in the Exposure Control rollout is turned off.
14. On the main toolbar, click Quick Render.

    The cylindrical canopy element is segmented again. When doing a File Link, you don't initially have control over settings like smoothness unless you use a preset that's modified to do so.

    NoteIf your cylinder is already smooth, it is most likely because you already have a low surface deviation setting from a previous file link procedure.

    

15. On the File Link Manager dialog, click the Files tab.
16. Make sure Show Reload Options is on and click the Reload button.

    The File Link Settings: DWG Files dialog opens.

    

17. On the Basic panel, set Maximum Surface Deviation For 3D Solids to .05.
    NoteLowering this value results in greater detail in the geometry.
18. Click OK to reload the scene.
19. Render the scene again.

    The object is reloaded and is smoother, as in the previous exercise using the Smooth-Angle setting, but there is a key difference that is most apparent when viewing the scene in Wireframe mode.

    

20. Right-click the User viewport label and choose Wireframe.

    

    Notice how many segments make up the geometry of Layer:CanopyEnd. The key benefit to using the Surface Deviation setting for 3D Solid objects is the amount of detail that comes across to 3ds Max. Geometry with higher quantities of faces and surfaces are more refined which results in a smoother model.

    If detail is still missing, you can choose Reload and further reduce the Surface Deviation setting.

21. From the Customize menu, choose Units Setup, and then on the Units Setup dialog choose US Standard, and make sure the associated settings are Feet w/Fractional Inches and 1/32.

Rescale units and find missing maps:

The units used in the AutoCAD drawing must match the units used in the 3ds Max scene. The scene can either adopt the unit system used in the AutoCAD file, or objects can be rescaled as they are imported into 3ds Max.

1. Reset 3ds Max and choose File menu > Open. Set the Files Of Type to VIZ Render (.drf) format.
2. Browse to the \tutorials\full_house folder and open tut_living_room06.drf.

   This is an Autodesk VIZ Render file created with Architectural Desktop 2004 that causes the Units Mismatch dialog to appear. The dialog indicates the DRF unit scale is in meters while the 3ds Max unit scale is in inches.

   

3. Choose Rescale The File Objects to the System Unit Scale and then click OK.

   If you installed 3ds Max to a drive path other than the default path, you may encounter the Missing External Files dialog. The Missing External Files dialog appears and lists missing map files that 3ds Max cannot locate. If the map files are stored on your system, you will need to add their folder path in the Configure External File Paths dialog when you click the Browse button. If the files are not available, you will need to substitute them from the Material Editor.

   

   

4. Choose Customize > Units Setup. Set the Lighting Units to American and click OK.

   

5. Render the scene.