Preparing a “Blobby” Object for Printing with Shapeways

I have been working with a 3D blobby object for some of my pilot studies on shape from shading and texture that I would like to 3D print. Back at Rutgers University, we had a MakerBot Cupcake, but now that I am in Germany, I need to find alternatives. I have been looking into getting the 3D object printed using but there have been a few hiccups along the way, so I wanted to describe my experiences in the hopes that it might help someone else avoid these issues in the future. The object was generated in MATLAB using a simple script (see 3D “Potato” Generation using Sinusoidal Pertubations) and rendered in our 3D environment:


So the question is: What do I need to do to get this 3D object printed at Shapeways? Click through to see the steps that I took to get this 3D model printed economically.
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Arduino FIO LCD Oscilloscope

It has been 7 years (!) since I posted my PIC18F2550 KS0108 Graphical LCD Oscilloscope code and schematics. I have long since taken the circuit apart, sold my PIC microcontrollers, and moved on in my life (as one can surmise from my most recent posts detailing my graduate and postdoctoral work). However, I still get inquiries about the Microchip PIC oscilloscope, so I decided to recreate it using a simpler setup using my Arduino Fio.


Here’s a short teaser video just to show that, yes, it works (going through a couple different sine wave frequencies, some random noise, etc. just to illustrate it working):

Click through the break to get more information on the setup.
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Effect of Environment Map Blur on Perceived Surface Properties

Here are a couple of quick demos, illustrating how blurring a cubic environmental map can lead to a change in the perceived roughness of the surface of 3D rendered objects.

I created a series of HDR cube maps using NVIDIA’s CubeMapGen (currently hosted on Google Code). Starting with the Debevec light probes, I applied a Gaussian blur with increasing kernel size (10°, 20°, 30°, 40°, and 50°), creating 6 cube maps (one for each blur). In the videos, the cube maps have increasing blur from left-to-right, top-to-bottom. Note that I did not tone-map or account for changes in overall exposure (so the specular reflections can appear blown-out, especially for the higher blurs). After the break, you can see the effect using different light probes (and different shapes).

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Misperceived axis of rotation for objects with specular reflections

Katja Dörschner visited JLU last week and talked about her work investigating structure from motion with specular reflections and textures (see more info in her recent paper: Doerschner, Fleming, Yilmaz, Schrater, Hartung, & Kersten, 2011). She showed an interesting situation where the axis of rotation of a 3D teapot was misperceived due to the motion of the specular reflections on the surface of the teapot (see: Yilmaz, Kucukoglu, Fleming, & Doerschner, 2011), an effect first demonstrated by Hartung and Kersten (2002).

Using the OpenGL/Psychtoolbox framework I have previously described, I replicated this interesting effect. When you play the following movie, a 3D sphere (with sinusoidal perturbations) is rotated. Note the axis of perceived rotation when the object has specular reflections (1st half of the movie) and when the environment map is “painted” onto the surface (2nd half of the movie).

The physical motion of the object is the same in both cases — the object rotates around the vertical axis. When the object only has specular reflections, it appears to rotate around an oblique 45° axis, but when textured it rotates around the vertical axis. After the break, I show similar effects when the object is rotated around the horizontal axis, 45° axis, and when the spatial frequency of the perturbation is manipulated.

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