Importing Models

3D Canvas provides the ability to import models from several popular 3D file formats.

To import a model:

  1. On the File menu, select Import.
  2. A sub-menu will provide you with a list of importable formats. Choose the format of the file you want to import.

Importing an model is often only half the job. In the world of 3D there are a number of ways of representing 3D co-ordinates. In 3D Canvas X represents left and right, Y represents up and down and Z represents depth. In other programs Y represents depth and Z represents up and down. Even those programs that agree that Z is the depth of the scene may disagree on which direction is positive and which negative.

Also some programs have polygon faces that are two-sided and some have polygon faces that are single-sided. Single-sided faces are visible on one side and invisible on the other. This is a little trick that results in higher rendering rates for real-time 3D software. Typically the invisible side will be inside a solid object and not viewable, so there is no reason to render it. Again, there is no consistency as to what defines the visible side. With some programs visible is a face that has points defined in a clockwise order relative to the viewing camera and with others it is points defined in a counter-clockwise order.

What makes things worse is that with some formats you never know what you are going to get.

With 3D Canvas Y is up and down and Z represents depth and away is positive. Also, a face is always single-sided and visible if its points are defined clockwise.

3D Canvas makes an effort to correct problems while importing, but does not always succeed perfectly.

This tutorial assumes that you have are rendering single-sided faces. To switch to this mode, select Options from the File menu, Select the Device tab and de-select Render Two-Sided Faces. Once you are happy with the imported model you can re-enable Render Two-Sided Faces.

 

This is a model of a helicopter that was imported from the wrl format. It is an ideal example because it shows virtually every problem that one could have with an imported model.

The object is inside-out. This means that the original program either had double-sided faces or faces that were defined to be visible if counter-clockwise.

You can correct this problem by selecting the object and clicking Operation-Invert.gif (516 bytes) which is the Invert operation. This turns the object right-side out. The Invert operation reverses the order of the points on the faces that make up the object.

 

TutorialImport1.gif (6857 bytes)
The object is now right-side out, but it still has problems. There is a hole in the object near its nose.
TutorialImport2.gif (7677 bytes)

 

Also, the rotor blade is only visible from the top. This is a fairly common occurrence. Designers often use a single polygon for very thin objects. Both this problem and the hole in the nose can be corrected.

The first step is to select the object and click Operation-Triangulate.gif (523 bytes) to Triangulate the object. This operation converts all faces in to triangles. More on this later. The next step is to fill the holes by clicking Operation-Solidify.gif (523 bytes), which is the Solidify operation. Note that the Solidify and Triangulate operations are only available with 3D Canvas XE and 3D Canvas Pro.

 

TutorialImport3.gif (7334 bytes)


This has corrected the problem with the rotor.
TutorialImport4.gif (6718 bytes)

 

It also filled the hole in the nose.

When solidifying objects 3D Canvas also deletes any orphaned faces. Orphaned faces are single faces that are not attached in any way to another face. Normally this is the correct behavior to fix model problems.

In this particular model however the designer decided to use a single face as the rotor and did not connect the rotor to the body of the object. Triangulating caused the single face that made up the rotor to be broken up into several connected triangles. This resulted in the rotor no longer being classified as an orphan face.

 

TutorialImport5.gif (7559 bytes)
Even after using the Solidify operation there can still be holes in an object. This is a relatively rare occurrence. This is typically caused by inward facing faces. The only way to cure this problem is to look inside the object for a face that is facing inwards.
TutorialImport6.gif (3615 bytes)

 

Using the navigation control you can move into the object and examine it from the interior. In this case there is a single inward facing face. It can be quite difficult to find these problems because it can be difficult to navigate within an object.

Once you find the problem face, select it and then click the Invert Operation-Invert.gif (516 bytes) operation to correct it.
TutorialImport7.gif (1263 bytes)

 

This has corrected the final problem with this model.

The final step is to select the object and click Operation-Optimize.gif (521 bytes) which is the Optimize operation. This operation removes any redundant faces and points. Note that the Optimize operation is only available with 3D Canvas XE and 3D Canvas Pro.
TutorialImport8.gif (3321 bytes)