Preetham Sky Model

One of the topics that I am studying in my PhD required an implementation of a sky model and we chose to implement the Preetham Sky Model.

Although there has been some criticism about the accuracy of the model (mainly for turbidities farther from the "clear sky" value), in my opinion, it provides a good approximation of what we should expect. We did however found that sky chrominance values were a little bit "too red" when we got close to sunset and sunrise.

Sun radiance is also tricky to compute: you need to attenuate the radiance according to your position on Earth, appropriately accounting for the traversal of the atmosphere (a big thanks to Kevin Beason and Pierre-Yves for helping with this :)).

Command Line Screen Capture

Under Mac and Linux it is pretty easy to do a screen capture using the terminal. On Windows, the story is a little different. I could not find an easy way to do this (please let me know if you know of any solution that ships with Windows).

Command line screen capture can be very handy if, for instance, you would like to setup a script to take a snapshot of your desktop at every 30 seconds - we did this for a recent project in order to record the process of modeling a specific scene in 3D using Maya.

Since I could not find a free solution, I decided to write a small program in C# that does exactly this.

screencap.exe is a small and simple program that can be called on the command with one argument: screencap.exe filename.png. It then records a snapshot of your desktop to the file filename.png.

Download link is provided below. Use it at your own risk.

download screencap

Computer Graphics Corner

Hello,

This is a work/fun computer graphics logbook to share things that I have either developed or find it interesting enough to deserve a post. As the title says, it is mostly related to computer graphics but not exclusively.

Cheers!