Friday, July 13, 2007


An antibug is a bug that combines with another bug and "fixes" it. Last night I found quite a few bugs and then had to spend most of the night finding the corresponding antibugs. These were infact quite big bugs in the sense that they where mathematical in nature. So if the size of the particles was changed, the results were quite simply wrong. Fixing this has meant some performance improvements as well. Unfortunately it means I didn't finish the plugin to a beta 0.5 yet. Also I have two more things to add to the list of todo's. Firstly I want to put in the advanced Options and a "reset" button.

So here is the suface version of the jump with the old code:
Old code Jump

Here is a new version of the jump with the fixed code:
New code Jump
New code Jump, Side View

Thursday, July 12, 2007

Reading the tea

So I hit the literature last night too see how much the field has progressed. How surfaces are generally done and incompressible SPH. There is finally a few papers on divergence free projection methods out there now. Because this has been used with other methods espisally for visually effects where accuracy is not so important (aka RealFlow I think) I was surprised that it took so long to be implemented with SPH.

In the future I will probably implement a divergence free fluid solver (via projection) as this will allow for very large time steps and allows for "vortex forcing", that is make the fluid more turbulent which is often the desired visual effect. As for surface tracking I will probably try a "colour" method to determine the normal at the surface. The unnormalized normal is a proxy measure of distance from the surface which provides a nice way to integrate with the isosurface solver in AoI.

Oh and here is a full simulation of the bent channel flow. It took 8 hours and has a maximum of 20000 particles with another 10000 boundary particles. This should be perhaps a bit faster really.
Zigging and Zaging
IsoSurface render

I also did a hydraulic jump. The iso render is cooking.
Jumping fluid

The reference to tea is because I cannot drink the large amounts of coffee I would usually drink. So now its lots of tea......

Wednesday, July 11, 2007

Final Beta 0.5 Stages

To my surprise I got to spend about 6 hours on the code yesterday. This was enough to get real close to a releasable beta.

What was added:
  • Moving fluid inflow
  • Moving fluid outflow
  • Improved GUI
  • Bounds parameter (removes particles outside the bound)
  • Max particle parameter
  • re-coded the interface between GUI objects and fluid Solver Objects
What needs to be done:
  • Add support for save and load.
  • Fix some minor bugs
  • Documentation. You will need some to use the beta (perhaps alpha?)
  • Add some parameters to the GUI, like max particle count.
  • Add tool tips. Makes docs easier.
There are some other issues that have come to light. First is that there will need to be some serious improvement on the surface representation to get a nice look. This could be some work and will be done later. Secondly without adaptive time steps there are large performance issues. In particular I want to add adaptive time steps both in time and space.

So the 2nd Generation Fluid solver will have adaptive time steps and support for multi core CPU's and will be what I work on after the beta release. The new surface stuff will need to be later. We will see. Anyway heres some movies of the latest incarnation of the plug in.

Ugly Surfaces
Same as above in preview mode(15MB)
30000 particles is a bit slow

Saturday, July 07, 2007


I have had a sore stomach for some time. It finally got bad enough that I couldn't go to work and had to see a doctor. To make a long story short I got my appendix removed, and spent most of last week in hospital. The good news is that the Austrian Health system is fantastic. All up its going to cost me 30 Euros!!. Seems I got lucky and went to one of the better Hospitals.

Of course the bad news is that work is now further behind along with the fluids plugin. I was hoping to do some while I was away from work. But unfortunately It looks like that won't happen. Sorry. There isn't much to do for a beta. But its still not ready. The goal is to be at version 1.0 by the end of the year.

I'm very sorry it won't be sooner. But quite a few things have gone a little pear shaped this year so far. Nothing serious of course, well not too serious, but enough that things just don't get finished when we wanted.

So thanks for all the comments, they do help. All i can say about the beta is that it will be out before duke nukem forever.