There is a method to blur them however. It requires blitting the FB and sending it to a blur shader, then rendering it with the proper blending over your screen. It's actually quite visually accurate and impressive, but shadows at a distance are quite blurry, and it's also hell on performance. We used to have this code in CRX, but have since stripped it out and gone solely with shadowmapping. The performance and appearance is vastly improved, although in our current code there are still the occasional annoying artifacts. We are still in the process of cleaning it up and optimizing, but you can view the code here - it's quite simple really. http://svn.icculus.org/alienarena/trunk/source/ref_gl/
The files to look at are:
http://svn.icculus.org/*checkout*/alien ... xt%2Fplain
http://svn.icculus.org/*checkout*/alien ... xt%2Fplain
The gist of what occurs is that you render the caster that is going to cast a shadow on the bsp into the depth buffer, then switch back to the main framebuffer and re-render the nearby bsp surfaces that the shadow will be on(rendering the shadow onto white surfaces, and blending into the scene). Then, switch back to the depth buffer and render any casters that might cast a shadow on the original entity(using the original entity's camera perspective), then render the entity using the completed shadowmap. This method has very little overhead as long as you're using VBO. The result is you get shadows on the bsp, and self shadowing plus nearby caster shadowing on the entity. My next goal is adjusting the frustom and perspective of the depth buffer and camera to make more efficient use of the depth buffer, and possibly get some better resolution and performance.
Here is an example of what it looks like - pay no attention to the fps, these shots were taken on my laptop which generally has roughly half the fps of what I get on my NV560 card. However, that same scene, when using blurred stencil volumes was less that half the FPS that you see here
