The rendering of transparent objects is not an easy task when using z-buffering. The reason is that the way z-buffering works requires to draw all transparent objects from back to front. However, this is not always possible since, for example, two triangles (or objects) could intersect each other, making it impossible to tell which one is in front of the other. To solve this problem, you need an algorithm which is order independent, hence the name order independent transparency. There are already a few algorithms for this: Using an A-Buffer, Depth Peeling , Screen-Door-Transparency and Stochastic Transparency, which I implemented as a test for another demo.
When I had a day off, I thought it would be fun to write a small viewer for LIDAR point cloud data.
Most of the LIDAR data which is freely available in a simple ASCII format or in the LAS file format. While it is quite easy to read the point data from both formats, the LAS format is more flexible and requires more implementation effort.
After writing the reader I tried to render aerial LIDAR point data directly, but it didn’t work as expected. The reason: The file format stores an x, y and z coordinate, but it doesn’t say in which coordinate system. Most of the time, cartographic coordinate systems are used. Fortunately, there is the PROJ4 which allows you to project the point data to a coordinate system which is more useful vor visualization. Since I’m more interested in terrestial LIDAR data, I decided to implement PROJ4 later.
There isn’t much terrestial LIDAR data available for free, however, the UC Santa Barbara provides terrestial LIDAR scans of their campus in the ASCII format. Some data sets are locally aligned, making them well suited for direct rendering.
The following screenshots show my first results, with three data sets which contain about 11.2 million points in real time:
I’m not sure if I continue this project, but the next steps would be to see how many more points can be rendered in real time, to implement a spatial hierarchy and to evaluate other rendering techniques.
My game OctaCore is now available for free : Download now from the OctaCore Homepage
It has been almost three years since my last post. There are two reasons: First, I’m busy at my current job as a software developer with ask GmbH, where we offer innovative visualisation solutions, automated document generation, and broadcast computer graphics. Second, there weren’t many exciting new algorithms or techniques in the last years. Combined with my lack of time and a few other reasons which I may explain in their own posts, I wasn’t able to do anything new worth posting.
So what’s new for 2013? As you can see, I migrated the old page to WordPress, giving the site a modern layout and making it easier for me to post new stuff. Since making new computer graphics demos with state of the art graphics becomes more and more time consuming, I’ll post less of them and try to focus on new articles and tutorials in the future.