Monday, November 30, 2015

Tone mapping colorful images

I recently noticed that a paper of mine from a few years ago had zero references.   This wasn't a paper with any deep research but instead was a "what is the simplest algorithm we can do that works" paper.   The idea was what to do with the practical problem of how most tone mapping pipelines kill bright blues.    Here is a figure from the paper on our inspiration for the user-controlled "dial" we added:

I think I figured out why nobody uses this paper-- we never put a copy online!   I just fixed that.  The paper is:
A copy is available near the bottom of my papers page.

Friday, November 13, 2015

iPad Pro with pencil stylus review

Summary:  Overall, the whiteboarding alone is reason enough for me to buy an iPad pro-- it has gone over that magic threshold of "good enough" that pads of paper will be a thing of the past for me.   Your excuse may be different (pencil drawing is a good one), so I think this device will be huge.

Dave Hart and Grue Debry got an iPad Pro with stylus for their company and they loaned it to me to try out tonight.   I used their limnu shared whiteboarding program to test it.

I tried it with the math I was messing with today (trying to meet Andrew Glassner's color space challenge to get uniformity into the prismatic color volume).

First, I **love** that I can rest my hand on the iPad while I draw (the iPad pro understands not to count that as a touch).

My hand is resting on the iPad as I draw and this is more important to my comfort than I would have thought
My biggest reaction was that this iPad is exactly the size I want.  It's about the size of 8.5 by 11 paper (actual working area size about 7 3/4" by 10 1/4"), so maybe that size evolved in paper to be the "right size" or maybe I am just so used to it that I like it.   Any bigger and it would be awkward to transport, and using this as a pad in a coffee shop is a great use case.   And of course you can pan so really it's a window into a much bigger sheet of paper.

The stylus is fantastic.   It feels good and has some features that has me not as eye-rolling about calling it a pencil.

As a white board marker I loved it.   Changing colors and nib sizes was more useful than I anticipated.   Using it as an eraser (which I had to do a lot as will be evident in some of the not very careful eases below-- I really do use limnu like a white board-- it's for blazing through ideas).   Here's my first screenful.  
A screenshot of my first session on limnu with the iPad Pro

 15 more 2x2 equations to solve (doing them as special cases to take advantage of zero dropouts) so I will definitely need the pan feature.   I used to use a big real white board or a giant artist pad for these situations, but I will most definitely use a tablet from now on.   Even without the saving and collaboration features I think it would be a win just because of physical portability and fluidity.  

Overall, the whiteboarding alone is reason enough for me to buy an iPad pro-- it has gone over that magic threshold of "good enough" that pads of paper will be a thing of the past for me.    I don't think it will make my laptop obsolete due to OS issues (Microsoft is making a better play for that now).   But the hardware of the iPad pro is in the laptop power zone.    John Gruber has a really interesting discussion of this hardware/software issue.

Tuesday, November 10, 2015

Cool 2D rendering project

Benedikt Bitterli has posted a really neat 2D rendering site that includes a javascript demo that he also has put on github.   (Via Dave Hart)

Monday, November 9, 2015

Uniform color models

I had an interesting discussion with Andrew Glassner (since this is often a ray tracing blog I'll tell the youngsters that Andrew is known for many things but he's also the inventor of the first sub-linear ray intersection algorithm!)  about the prismatic color model I have been touting.    Andrew points out that while it retains the good properties of HSV it also retains its worst property: terrible color uniformity.    The color scientists have long rightly held that it would be nice if a color space had intuitively similar changes in color for similar changes in distance in the space.   The so-called MacAdam ellipses on the CIE diagram (where each ellipse holds a collection of colors that are nearby) can be used to warp the CIE space to a more uniform one.

Each MacAdam Ellipse has a set of colors you can barely tell are different.   A "uniform" color space would have disks of the same size for these.   Source wiikipedia.

Andrew rightly points out that for a color space to be kick-ass (my term) it should be at least somewhat uniform.   So a challenge to all of you out there: create a uniform space that is RGB-centric.   Or if you know of one, tell me!

Thursday, November 5, 2015

Tech Report on the Prismatic Color Space

Dave Hart and I have written a tech report on our Prismatic Color Space.  Please let me know if you use it for anything fun.