pyro experiments

[wolf_cub_one]

I started testing pyro again due to itriix's various post on issues that he was going through while trying out the pyro tools.

My first test was very promising. I got very nice details without tweaking the pyro shader. Only issue was that the smoke was building up really fast and quickly collided with the bound box.

Next I tried to control the speed and also to maintain the details. I increased the pyro bounding box a little to give it more room. I lowered the speed and changed the cooling rate down to try to slow the smoke down. I added a gas dissipate dop and set the control field to heat with an evaporation of 0.3. I was getting a good slow fade and better control of the smoke with some loss of details.

Lastly, I wanted to fade it even more and stop it from reaching the top of the bound box. I added a gas calculate dop and this really faded the smoke but with the cost of losing a little more detail.

I used a lowres of 150 which took between 15-20 minutes per test and an upres of 250 which took about 30-45 minutes per test.

Well I got to go and watch District 9.

cheers

pyro_250_start.mov

upres_250_gas_diss.mov

upres_250_gas_diss_gas_calc.mov

[wolf_cub_one]

I've been doing a few more experiments to test quality vs. speed in the pyro tools.

I made a pyro scene where I used a lowres 150 sim and uprezzed it to 300, and it took about an hour and 30 minutes total for sim time based on a 90 frame animation. Then I took the same scene and just did a lowres 300 sim. That took 2 and a half hours. If you look at the accompanied quicktimes, you can see the difference between the results. Houdini actually does a pretty decent job of uprezzing and saving you time. However, the 300 lowres version does look slightly better. What really stands out, at least for me, is the life in the flames. It's a toss up but in the end it's all boils down to what is more important to you --speed or quality?

I've also been experimenting with fading the smoke. Even though you can get great results using either the Gas Dissipate Dop, the Gas Calculate Dop, or a combination of both to fade the smoke, I prefer a different route. The problems with doing it in dops for me is that if your results are not what you want you have to change the settings in dops and redo the sim and see if it's better with the changes. It's really time consuming. I chose to set up a density ramp using a VolumeVop and blending between this ramp and the original density field of the sim. Doing this a this at the sop level is faster for me since I can go directly to a frame and just render to see how the fading is going on that frame. Currently, I have control over what frame to start the fading, when to end the fading, and the maximum level of fading allowed. I've including a quicktime showing a quick fade between frames 35 to 90 but topping out at 70%. Here is where I need a little help/hint. I next want to control the fading based not on time but on the height of the smoke but I'm not sure how to approach this. I'm sure it's simple but I was hoping someone could give me a hint on how they are are currently doing it. Any help would be greatly appreciated.

cheers

upres_300_from_150.mov

lowres_300.mov

lowres_300_fade.mov

[kensonuken]

can u pls upload the hip file? looks good though

Edited September 5, 2009 by kensonuken

[wolf_cub_one]

I'm still experimenting. Just changed the way I'm fading the smoke. Now I'm just fading it like I did with a Gas Calculate Dop but at the Sop level. Just started playing with Scattering again. It seems that you save time writing the pc files by using the lowres sim and not the upres sim. I did some preliminary tests and it seems to have no affect on the final look, but you save a lot of time using the lowres sim for pc writing. Need to do some more tests. I probably spend another week testing and then I'll move on to what I've been wanting to get back to now that I have more free time--water and liquid simulation.

Once I'm done testing you can have the hip file. Remind me again in about a week. I want to get the bugs out before sharing anything. The only thing is that it'll be a .hipnc file since I couldn't continue my AUP and I'm stuck at 9.5 so I hope that's OK.

Anyone have any suggestion for fading the smoke based on height. I have some ideas but not sure if they will work, but I would still appreciate some help.

cheers

[wolf_cub_one]

It's starting to look OK. The scattering really makes it look better. I had to crank up the scatter settings and also the density of the smoke to really start to capture the feeling that there is heat coming from this pyrofx. The nice thing is that since I'm using the lowres sim for the pc generation I didn't take a big hit in the sim time at all. This render took 2 hours and 30 minutes for a 90 frame animation. My processor is a Q6600 running on Ubuntu 9.04 64-bit.

I still need to tweak the look still. Then I'll start looking into optimizing the render time. Any hints would be great. After all that I'll look into how to light a scene with the pyrofx. I'm going to take a break since it's a long weekend and enjoy the holiday.

Have a great weekend everyone

pc_render.mov

[wolf_cub_one]

Been testing different ways to use pyro as a light source. Found different ways to fake it. Here is one way based on the distribution of the point clouds sim from the scattering. Moving on now to water.

pyro_light.mov

[Jamel Drayton]

Hi I have an really newb pyro question, I followed the tutorials online the one at the side effects website and I am a little confused on to how houdini pyro fx renders out. I follow that you render the scatter, then you can render the low res or hi res. But then what do you do with them though, Can't composite that in AF or something. I try to render it through out mantra I get fire but the smoke doesnt show up. and it just doesnt work at all when I turn on depth M shadows,(which needs to be rendered as a rat.) sorry I could be going about this all wrong, Im not like totally lost, I just need to be pointed in the right direction......

Thanks for understanding

heres the file just in case.

pyr0.hip

[wolf_cub_one]

Hey Jamel,

What is the problem exactly? Do you mean it doesn't render out at all or that you can't render out different render passes?

Oops, forgot to add this:

If it's setting up render passes then read this thread:

Edited September 14, 2009 by wolf_cub_one

[Jamel Drayton]

Hey Jamel,

What is the problem exactly? Do you mean it doesn't render out at all or that you can't render out different render passes?

Oops, forgot to add this:

If it's setting up render passes then read this thread:

thanks for the link I think that will help me out later, once I understand whats going on. Sorry for not being clear, lets say I have a fire burst with some smoke coming out. What are the steps you would take to render it? like I know there's more to it then just hitting the render button. It involves generating a point cloud, shadows, exporting the render from low. upres, ect. the tutorials I have seen are not so obvious to what you do with them once your done generating them.

sorry for the basic question maybe some other pyro beginners will fine some use of this. On an other note I really like the progress of the tests you have done. When your done it would be nice to see how you went about things.

Edited September 15, 2009 by Jamel Drayton

[wolf_cub_one]

I'm just doing very basic tests, nothing special but thanks.

What version of Houdini did you use to set up your file? From my experience, the very early versions of H10 seems to have a slightly different pyro shader. Is this correct Mario?

As for the basic render setup, let start at the very beginning and please use the latest version of H10 so that we are working with the same results:

--add an object(sphere, tube, whatever)

--click what you want from the pyrofx tab(fireball, flames...)

--add camera and light with shadow set to shadow maps

Now the basic scene is set up. Watch the videos for more detail explanations.

From what you stated, your problem is dealing with the rendering. Here are the basic sets so that we're both on the same page(just for the lowres, since it's basically the same for both):

--Sim Out Lowres:

1.Hit render in the export to file tab on the Dop I/O node within the node labelled lowrespyro with the range that you want and with the file padding that you want

2.Once done you can set it to Load from Disk to read these .bgeo.gz files instead of it redoing again for a render

--Generate Point Cloud:

1.Make sure Scattering is check on the Scattering tab on the VEX Pyro shader.

2.Set a path to save both the Smoke PC File and Fire PC File with the correct file padding(ex: my_smoke_pc.$F4.pc)

3.Click the Generate button and a image viewer window will pop up.

4.Let it finish rendering and once done you can just close it.

The important thing with generating the point cloud is that you need to make sure the camera you are looking through for the point cloud is able to see your whole pyro scene as needed for your animation. You can use the camera that you are using for your animation or use another camera that is viewing the entire pyro explosion. Another thing from my experiments was that once you generate the pc and you are happy with it, you can just reuse this for the upres instead of regenerating it based on the upres sim. Saves time.

That's about it. Render your animation. It's should be that simple. Not sure what else to tell you unless you can tell me exactly what and where things are going wrong.

Edited September 15, 2009 by wolf_cub_one

[Jamel Drayton]

I'm just doing very basic tests, nothing special but thanks.

What version of Houdini did you use to set up your file? From my experience, the very early versions of H10 seems to have a slightly different pyro shader. Is this correct Mario?

As for the basic render setup, let start at the very beginning and please use the latest version of H10 so that we are working with the same results:

--add an object(sphere, tube, whatever)

--click what you want from the pyrofx tab(fireball, flames...)

--add camera and light with shadow set to shadow maps

Now the basic scene is set up. Watch the videos for more detail explanations.

From what you stated, your problem is dealing with the rendering. Here are the basic sets so that we're both on the same page(just for the lowres, since it's basically the same for both):

--Sim Out Lowres:

1.Hit render in the export to file tab on the Dop I/O node within the node labelled lowrespyro with the range that you want and with the file padding that you want

2.Once done you can set it to Load from Disk to read these .bgeo.gz files instead of it redoing again for a render

--Generate Point Cloud:

1.Make sure Scattering is check on the Scattering tab on the VEX Pyro shader.

2.Set a path to save both the Smoke PC File and Fire PC File with the correct file padding(ex: my_smoke_pc.$F4.pc)

3.Click the Generate button and a image viewer window will pop up.

4.Let it finish rendering and once done you can just close it.

The important thing with generating the point cloud is that you need to make sure the camera you are looking through for the point cloud is able to see your whole pyro scene as needed for your animation. You can use the camera that you are using for your animation or use another camera that is viewing the entire pyro explosion. Another thing from my experiments was that once you generate the pc and you are happy with it, you can just reuse this for the upres instead of regenerating it based on the upres sim. Saves time.

That's about it. Render your animation. It's should be that simple. Not sure what else to tell you unless you can tell me exactly what and where things are going wrong.

Thank you this is exactly what I was looking for. Now I can focus on controlling the fluid effects to get a good look.

Edited September 15, 2009 by Jamel Drayton