Archive for 2007

Plücker coordinates not so good for you?

Tuesday, July 17th, 2007 by Bramz

Christer Ericson, author of Real-Time Collision Detection has written a little article on Plücker coordinates and why they are considered harmful. It’s great. I never really understood what all the fuss was about, as I could do the Plücker coord tricks as easily with basic 3D linear algebra and its triple product. So, I’m glad […]

new URL for Subversion access

Tuesday, June 12th, 2007 by Bramz

As of 28 June 2007, Sourceforge will decommission the SVN access URLs starting with They are replaced by URLs with the project names in front. For LiAR, this looks like The new URL scheme is part of an upgrade of the Subversion access method to improve its stability. If your local working copy […]

we’ve moved to

Thursday, February 8th, 2007 by Bramz

We’ve successfully moved the LiAR home page to This should allow us to upload bigger renders, and get better search engine coverage. The old URLs starting with should redirect traffic to the new site so that no links get broken. Share and Enjoy!

things learnt while installing VS2005 SP1 …

Wednesday, February 7th, 2007 by Bramz

If you’re planning to install Visual Studio 2005 Service Pack 1, keep this in mind: Make sure you have at least three gigs of free space on your C: drive. To be on the safe side, make it four gigs. Windows Update tries to shove this up your arse as a security update, but don’t […]

overriding default compiler options in distutils

Monday, January 29th, 2007 by Bramz

While debugging another segmentation fault on linux, I was trying to run LiAR in gdb (actually KDbg). The program crashed somewhere in an allocator, but the reason why was almost impossible to see. The debugging experience was crippled because distutils compiles with full optimization -O3 by default, at least my linux box. If I was […]

shared libraries, RTTI and dlopen

Sunday, January 28th, 2007 by Bramz

When I tried to run a first render in linux, I got a segmentation fault in the photon mapper because there were no lights. Of course, this shouldn’t cause a crash (fixed by now), but why were there no lights? I was pretty sure I defined one, and a quick investigation of the scene graph […]

the bumpy road to the linux build

Saturday, January 27th, 2007 by Bramz

The description of LiAR says: “‘LiAR isn’t a raytracer’ is an open source, cross platform, object-oriented and extendable ray tracer written in C++ and Python by Bram de Greve”. However, that’s not entirely true since currently, LiAR only runs on the Windows platform. It’s time to live up to the promise. To be honnest, I’ve […]

clip mapping

Tuesday, January 23rd, 2007 by Bramz

I’ve added clip mapping (*) to LiAR, which is some sort of alpha channel for surfaces. It can be used to create holes in a surface using a texture. The texture is compared to a threshold to determine where the surface should be removed, so that rays can travel undisturbed through the removed parts. This […]

subdivision surfaces and UV interpolation problem

Wednesday, January 10th, 2007 by Bramz

I’m trying to use the subdivision surfaces I’ve implemented to get a smoother surface for car i’m rendering for PHD Motorsports. The original model has UV coordinates that need to be interpolated as well. As each triangle is split in four, each edge is split two. I’ve been using the naive assumption that for the […]