In a previous article, I began using 123D Catch to create a 3D model from still photographs. My project is to print some replacement feet for a patio chair. These were originally made from injected molded plastic. Several have gone missing over the years. Before I can print the replacements, I need a model. I can create this in CAD, or by using 123D Catch. I thought the latter would be easier and faster. But from where I am on the learning curve, it might not be.

There seem to be two problems using 123D Catch to create a 3D part replacement model. The first is specific to my part. It is nearly symmetric, the same on both sides. The part is basically the same on its narrow sides, and nearly the same on its wide sides. The main difference is that one of the wide sides of the part is flat, the other is sculpted. Since these two sides are so similar, 123D Catch seems to try to combine them into one side. The result is a blurred capture shown in the picture on the left, above.

The other problem is that when using 123D Catch, the software seems to think all of the pictures are taken from just one hemisphere. This is shown in the middle picture, above. I think this relates to the near symmetry. But, also, 123D Catch is rejecting most of the pictures taken on one side of the part, and accepting pictures taken on the other side.

So, I put some red markers in different places on the part, as shown in the picture on the right, above. These were just small pieces of red duct tape. I made sure that I placed them in different locations on the different sides. My theory was that the non-symmetrical placement of the red markers would help 123D Catch differentiate between the sides. As shown on the right, above, this did not help.

I concluded that the problem was ambient lighting being different in the different directions. These captures were taken outside on a relatively cloudy day. But still, lighting in each direction varied.

Using 123D Catch – Almost Success

This morning, before the sun came up, I tried another capture session in the kitchen using 123D Catch. The kitchen is lit by a “sunshine ceiling” and there was no sun shining through the windows. And, what do you know? Almost success. I got an almost perfect 3D part capture using 123D Catch, as shown below.

There are still some “holes” in the model on the top and bottom. I need to take more pictures from those directions. This capture used 36 pictures. Hopefully, the next article will describe complete success. Once I have the complete 3D part replacement model created using 123D Catch, I will move on to editing the model, and then printing the part.

This has all taken far too long, but using 123D Catch requires experimentation and learning. The main things that I have learned are that:

• The most critical aspect of capturing a 3D model using 123D Catch is smooth ambient lighting in all directions.
• If your part is near-symmetrical, apply random markers to help the software differentiate between the various sides.