Conveying Shape: Lighting, Shading and Texture
From Visualization Sp06
Lecture on Apr 4, 2006
Readings
- Perceiving Shape from Shading. Ramachandran (pdf)
- Using Non-Photorealistic Rendering to Communicate Shape. Gooch and Gooch. (web)
- Conveying Shape and Features with Image-Based Relighting. Akers et al. (html)
Optional Readings
- The lit sphere: a model for capturing NPR shading from art. Sloan et al. (html)
- Automatic lighting design using a perceptual quality metric. Shacked and Lischinski. (web)
- Maximum entropy light source placement. Gumhold. (ieee)
- Light Collages. Lee et al. (html)
Gwyu - Apr 04, 2006 04:00:02 pm
So here's a movie of the hollow mask illusion with a real mask. What's cool about this demonstration is that it's outside, so the illusion doesn't seem dependent on extremely controlled lighting conditions. However, it seems like cheating a bit because they paint the inside of the mask to emphasize the facial features. I'll try to find the one I saw before where the inside was unpainted.
Found it. It's at the bottom of the page.
Bryan - Apr 06, 2006 09:46:21 am
Reading Gooch's work makes me wonder whether the speed with which many modern renderers run would make it possible to automatically generate visualizations of shape and structure using a large family of parameters, displaying results to users who could compare two renderings, rate them, and guide the continued generation of renderings until an "optimal" visualization is reached. I liked the examples they present but they still seem pre-mediditated and so are probably still influenced by what the authors thought would work well.
Maneesh - Apr 07, 2006 11:23:47 am
Bryan - A design galleries approach to lighting design would put more control in the hands of the designers. Joe Marks has done some nice work in this direction (see the design galleries link) but I don't think they applied it to the Gooch model. One issue is that when the parameter space is large it can be difficult to show all the options at a reasonable size.
Noaa - Apr 08, 2006 04:39:25 pm
That mask thing seriously freaked the bejeezus out of me. I honestly had a hard time looking at it because I was freaked out. It's so strange when in classes you are shown things that put the limits of your perception and the subtlies of what the mind can process so distincly on display. Things like the mask, the gestalt principles, etc. It's kind of scary to be shown just how much you are not in control of your own perceptions, that even if you know full well that something isn't real, you can't help but see it anyway. Reminds you of the limits of being human I suppose.
Noaa - Apr 08, 2006 04:39:25 pm
That mask thing seriously freaked the bejeezus out of me. I honestly had a hard time looking at it because I was freaked out. It's so strange when in classes you are shown things that put the limits of your perception and the subtlies of what the mind can process so distincly on display. Things like the mask, the gestalt principles, etc. It's kind of scary to be shown just how much you are not in control of your own perceptions, that even if you know full well that something isn't real, you can't help but see it anyway. Reminds you of the limits of being human I suppose.
Yi-Tao - Apr 10, 2006 09:23:41 pm
The paper by Shacked and Lischinski was quite interesting. The details that can be seen in the optimized rendering of the steamboat is quite impressive. However, they don't go into any details about how they plan to deal with highly reflective surfaces. In that case, placing too many lights would make the object look odd. So I'm wondering if there's been any further work on the subject.
Brien - Apr 10, 2006 10:09:44 pm
I like the varied line weight effect mentioned on "node 5" of "Using NPR to Communicate Shape" (the right-most images). Tapering a line into the background adds perspective and adds to the interaction with the viewer. Something like a laser beam, the tapered line blasts my focus across the object, enhancing the overall experience. Maybe it's something else about Node5 that makes me feel sci-fi.
Raymond - Apr 11, 2006 02:19:11 pm
Here's a link to the optical mask illusion with the computer generated and real-life mask (insides not painted) side by side: optical illusions. Also note that if you go back to the main page one of the image links near the bottom has the mask rotating top to bottom and it also produces the same effect!
One the main page, http://www.michaelbach.de/ot/ there is also a section on optical illusions based on luminance and contrast for any that is interested.
Mattkam - Apr 11, 2006 02:34:54 pm
To follow up on the website that Raymond has found, there is this optical illusion that some of you might have already come across: http://www.michaelbach.de/ot/fcs_SpatFreqComposites/index.html. I'm not sure if bluriness and shading are related, but it does seem that if they are, then this is an example of how shading can be applied to convey different shapes.
