Wednesday, February 22, 2017

More Robot Driven Light Paintings

I created some new light painting. This is an extension of the work I originally posted about here. Using some new path code and a battery pack to power the lights gave me more freedom of movement. The photographs were taken by my Taubman College colleague Asa Peller.

Here's the robot and tool used to generate the images. The robot is a Kuka KR60. The custom made tool is 40" long and contains a line of 60 LED lights. Each light can be controlled individually and display up to 16 million colors. A small Arduino microcontroller controls the lights.

Here's a video demo showing the various light modes:

The images are captured using long exposure photography. A camera on a tripod sits in a dark room facing the robot. The camera shutter is opened, the robot moves along a curved path with the light tool on. When the robot stops the shutter is closed. The robot is in motion for about 30 seconds to generate these.

These images give you a sense of the space the robot moves within:

Here's a screen capture of the simulation of the robot. The robot follows a path curve. The path curve is divided into a certain number of points. For each point the tool remains tangent to the curve at that point. By changing the number of points you can dramatically change the nature of the motion generated.

It's a pretty close match between the simulated path and the actual robot path. But the spline interpolation is different between NURBS and what Kuka is doing with the Spline Movement motion type so they are not an exact match. It's always interesting to see the images produced by the robot.

Monday, February 20, 2017

ZBrush Portrait Sculpt Produced on 3D Printers

I finished a digital portrait sculpture and decided to realize it with 3D printing. I produced several reliefs prints and one full 3D print. This images shows three separate prints in a Walnut frame, 22" x 12" x 1.5".

Here's the full 3D print:

Sculpting Process

Here are some pictures of the digital sculpting process. I'm using a Windows laptop with ZBrush software. I can move around the model freely on a mobile stand.

I currently use a Wacom Intuos tablet (after using a Wacom Cintiq for years). I prefer this - it's cooler on the hand and much more of a relaxed position for my arm. And I can go for several hours without plugging in. Plus my hand is on the keyboard for shortcuts and Shift/Ctrl/Alt key combos which are essential in ZBrush.

Preparation for Fabrication

Here's the finished ZBrush model ready to prepare for routing and printing. At this point the hair, eyes, and face/shoulders are all separate objects. Doing that makes it much easier to sculpt. But they need to be one mesh to mill. The polygon count in ZBrush is 4.3 million faces. The polygon count needs to be reduced - a lot. Both DecimationMaster and ZRemesher were crashing in ZBrush. Very unusual. So I did it in Rhino using the ReduceMesh command. This is actually not nearly as good. But it was adequate.

Here's a comparison 4,300,000 faces on the left versus 360,000 on the right:

I had to fix a few really tiny naked edges and two non-manifold edges. This is fairly easy using Rhino's mesh tools (mainly DeleteFace and PatchSingleFace). I have to say - having a 3D Connexion mouse (I have the cheapest one) makes viewing and understand what to eliminate much easier. That's because you can twist the viewport so much more readily to see what's happening. In these detail cases you have to move the model while looking to understand it.

3D Printed Reliefs

Once fixed and solid I scaled 1D to push into a relatively high relief. Then I BooleanUnion a box onto the back. Here's the result - 9" high, 6" wide, 1.5" deep: 

Here's a three-quarter relief. Similar technique except rotating the 3D model first, then scaling along the axes of the CPlane. This is lower, about 1.3" thick total. 

Here's a side relief. Lower still - about 1.1" thick total.

The prints were done on a Stratasys Dimension 1200e, the one on the left. This is a ABS printer which requires support material.

The support material needs to be dissolved from the 3D print. It is soaked in a warm detergent bath for a few hours to do so.

Below you can see most of the darker support material is gone. A little remains on the edges - back into the tank. Also of note in this photo - that one was printed with the back plate flat on the printer bed. So the layers of the print look like contours across the face. Zoom in - you'll see this is a terrible idea. The print comes out just fine when printed vertically (face forward, not up).

Here's a comparison with the model, computer model, and 3D print.

In the Round 3D Print

The full 3D print was done on the printer below - a Stratasys uPrint. The printer took about 15 hours to complete the job:

Here's the finished print mounted on a Walnut base:

A Version Produced in Wood

Here's a post on CNC routing this same form in wood.