Hi
I am exploring pyro.Could some one guide me how an explosion from a window can be made.
do we need to shape the motion using particles and gas to particle field or we just need to tweak the values in pyro solver.
Any pointers on this would be really great for me to start thank you very much

What tests have you done so far ? if you look at all the shipping examples with Houdini there is enough information to let you certainly make some small tests

rob

hi
I did test by animating the fuel+temperature at high levels.
but seeing few examples from odforce.its seems that we need to use gascalculate fields for high moving fluids.so I did that way and I dont know how to proceed after this.the sim doesnt look like explosion as the fluid was attached to every particle.so i increased the max substeps to compensate that.but not getting perfect results

divergence is your friend (expand fluid shelf button). But making a good explosion takes time and depends on many factors (divergence, fuel distribution, initial source fields, diffusion, flame length, heat contribution etc.)

I would start off simple, get a look that you can work on. Don't try to nail it using a worst case scenario. Houdini 12 offers a lot of fluid customization methods and most if it depends on the right initial data (collision, fuel, temperature), shape operators and general sim settings (diffusion etc.) See for yourself what happens if yoyu alter these settings and the influence it has on the sim.

hi cklosters
thanks for the reply.I am a beginner in pyro and now learning.could you share a simple example on creating divergence fields.I seen few posts in odforce but it seems to look complicated for a beginner like me.So it would be great if you could help in this.thanks

Here are some basic pyro tips on sources.

Always flip the various field visualization tabs on and off on the Smoke Object DOP. Create a floating parm pane or some other way to keep this up all the time. It is very common to toggle off Multi Field and turn on temperature, fuel, divergence, burn, heat, velocity (especially velocity) and the others so you can see what is happening in the sim.

Source Emitter is everything for the first 3-5 frames
For the first 3-5 frames of the explosion, the source geometry is everything! By default the shelf tool creates hollow emitters. Make them solid (read notes in the hip file) and increase the noise frequency to get more detail in the initial sim. Tweak the source in SOPs and only play back the first 5 frames of the sim to see the effect this has on the sim. I find it dramatic.

Add Point Velocities
Add initial point velocities normalized in SOPs and then scale them up in DOPs. You need lots of points on your source geometry to get a decent vel. I will sometimes create two Fluid Source SOPs, one to build the density/temp and the second following a Scatter SOP with velocity attribute sculpting to create vel fields and merge.

With the emitter roughed in, go to DOPs and tweak the combustion settings.

You can call it a day and start tweaking out the pyro sim settings to get a nice explosion.

See explosion_basics.hip

As for divergence, the Gas Released Parameter maps pretty much directly to the expansion of the explosion. Notice how it is carefully animated to boost values at 100 for the first few frames to get things moving along.

thanks a lot buddy!!!
your scene and tips was useful