One extension I had been planning for my previous project involving terrain meshes was the addition of satellite imagery to add color to the models. Landsat, in addition to enabling important climatology research and other science missions, turned out to be a great source of open data to use for this.
A while back, I thought 3D printed models of the local terrain might be a cool gift idea. To make this a reality, I have implemented a simple Python utility to convert publicly-available terrain data into a format suitable for 3D printing.
In my last post, I explained how I reverse-engineered the Alesis SysEx protocol and detailed my findings. Now, two months later, I’ve finally decided to implement a tool for configuring these controllers on Linux.
I recently got back into music production and decided to order myself a MIDI controller. I got a few recommendations for the the Alesis V25, so I went ahead and ordered it. However, I was less than pleased to find that its configuration software wouldn’t run on Linux, even under Wine. Of course, this prompted me to reverse engineer the protocol that lets the software talk to the keyboard.
Yesterday, I took a glance at the Wikipedia page for the circular buffer and was intrigued by an alleged optimization technique that I was not familiar with: A circular-buffer implementation may be optimized by mapping the underlying buffer to two contiguous regions of virtual memory. (Naturally, the underlying buffer‘s length must then equal some multiple of the system’s page size.) Reading from and writing to the circular buffer may then be carried out with greater efficiency by means of direct memory access; those accesses which fall beyond the end of the first virtual-memory region will automatically wrap around to the beginning of the underlying buffer. When the read offset is advanced into the second virtual-memory region, both offsets—read and write—are decremented by the length of the underlying buffer