More Tips for Importing Files from AutoCAD to 3DS

When you import a dwg file from AutoCAD to 3Dstudio, examine the model carefully. You might notice that some surfaces/objects are missing! There could be any number of reasons, and below are the most typical ones. At the end, I also add one useful tip regarding changing color of objects for easier selection.

1. Options in the dialog you get when importing AutoCAD .dwg file into 3DStudio
   1. General Options:

      Skip off and frozen layers:

      Setting this option on provides no transfer of objects on AutoCAD layers that are off or frozen

   2. Geometry Options:

      Weld:

      This option combines adjacent surfaces if their edge points are closer than the threshold. The advantage is that this usually makes your file smaller and faster to render. However, if you turn this option on and use a large threshold value (relative to the precision of your model), vertices of objects may get welded incorrectly and you will have some surfaces (ones smaller than the threshold value you set) disappear in 3DS. If that is the case, try using a smaller threshold value, or turn this option off completely.

      Unify Normals:

      If your model is made by AutoCAD solid modeler, set this off. VIZ will not change the visible side of solid's surfaces, which are supposed to be adjusted correctly by AutoCAD already. If your model includes objects made by AutoCAD surface modeler, you might like to turn this on. VIZ will then try to adjust the visible side of each surface.

      ACIS Options:

      the values specified here will control the number of facets derived from an AutoCAD solid which has curved surfaces. Decreasing this value makes the curved surface smoother at the cost of larger data and slower speed. I recommend you to set this to a larger number first and check the transfered curved surfaces in 3DS. Then decrease the value and re-transfer the model only if you need a finer model. For planer surfaces, this value has no effect.

2. Force 2-sided option
   By default, 3DS sees only one side of any surface and not the other side. The visible side is the side of the surface normal direction. Most surfaces made in AutoCAD using solids look fine with this setting. However, if you find some objects with lost surfaces from one view angle but not in another, it is likely that the file transfer from AutoCAD to 3DS could not orient the surface normal correctly. To change the setting so that 3DS sees both sides of the surface.
   1. Quick viewing in viewport's shademode:
      Right click the viewport's name>configure>Rendering Method>Rendering Option>Force 2-sided
      Right click the viewport's name>configure>Rendering Method>Rendering Level>Smooth
   2. Rendered Image:
      Rendering>Render...>Common Parameters>Options>Force 2-sided
      This method is a quick fix that applies 2-sided option globally to all the surfaces and slows the rendering. Later on, you may instead want to consider using 2-sided option per object's material, or flipping the surface normals manually.
3. Object's color
   By Default, objects in 3DS gets their color from AutoCAD. Thus white objects in AutoCAD becomes white in 3DS. This is a problem. Why? 3DS indicates object selection by turning it white in wireframe mode and if the object is white to begin with, you cannot tell if it is selected of not. So, it is recommended to change the color of an object from white to something else. You can just select Modify button (One of the 6 buttons on the right of 3DS screen which looks like this ) and click a white object. The area below the button tells you its name and color. Hit the color and change it. Then deselect the object to see that the object got the color you chose. You can also change the name of an object this way.