adnormaly long render times with pyro after generating point clouds

[Jamel Drayton]

Ok just when I think I have this pyro thing figured out, I always get thrown a curve ball. Im trying to archive a explosion with the fireball. So far I would say I am fairly happy with what I have. Every thing seems to be working fine until its time to generate pointclouds. after that the render is sooo slow. your talking a good 15-20 mins a frame if im lucky i have a pen 3 with 2 gigs of ram. Should it be going this slow I mean im not even on hi res. on top of that, I cant even batch render. I attached the file if any one wants to take a look. im not sure what went wrong

[Mario Marengo]

Every thing seems to be working fine until its time to generate pointclouds. after that the render is sooo slow. your talking a good 15-20 mins a frame if im lucky

It seems you forgot to actually attach the file...

My guess is that you have the "Atten Method" in the "Scattering" tab set to "Real". If so, set it to "Approximated, No Shadows" and see what happens. I believe the differences between these attenuation modes are covered in the docs (together with their relative costs).

I have no idea why the "Fireball" preset sets this to "Real", as the "Real" setting casts a shadow ray per PC point and is therefore, by definition, excruciatingly slow (it does produce a more correct result, but at an incredible cost)... I wonder if I should remove it altogether in the next version...

There are other factors which may be contributing to the slowness though, so it would help if you post your file.

HTH

[Jamel Drayton]

sorry I could have sworn I attached it

Explosion4_bak1.hip

[Mario Marengo]

sorry I could have sworn I attached it

Yup. What I suspected: the attenuation method was set to "Real".

Try this (go to frame 33 or so):

Explosion4_bak1_mgm.hip

A few notes:

1. Note that for very homogeneous smoke/fire, you can get away with a very sparse point cloud. (i.e: instead of the recommended 10*stepsize, you can go higher). In this attachment, I've set it to 100*stepsize and you get similar results for cheaper.

2. The pointcloud camera doesn't need to be miles away -- just far enough to capture the whole cloud but not much farther. I've adjusted your cam2.

3. careful that the reset rate of your dual rest fields matches that of the sim (which is set to 50 frames in your case). I adjusted the shader's reset rate to match.

4. Your light wasn't casting shadows. I added depth map shadows to it.

HTH.

[Jamel Drayton]

Hey First of all thanks man for helping me solve that point cloud situation. I was able to cut my render time down by so much. So I rendered my explosion out following the settings you gave in the file provided. It low res some 14 hrs to render. Im thinking of going upres and prob let that render over night and while im at work next day. Before I do that I wanted to know if theres any thing you think I can do to improve the look of it. Any crit would be great.

Thanks again

Explosion_lowRes.mov

[wolf_cub_one]

Hey Jamel,

I think something is definitely wrong. It shouldn't take 14 hours to render that scene. It should take about 1 hour, but then looking at the fact that you are using an older computer might be the issue. If you have access to a faster computer, you should do a render test to be sure because 14 hours is way too long.

[Ratman]

Yup. What I suspected: the attenuation method was set to "Real".

Try this (go to frame 33 or so):

Explosion4_bak1_mgm.hip

A few notes:

1. Note that for very homogeneous smoke/fire, you can get away with a very sparse point cloud. (i.e: instead of the recommended 10*stepsize, you can go higher). In this attachment, I've set it to 100*stepsize and you get similar results for cheaper.

2. The pointcloud camera doesn't need to be miles away -- just far enough to capture the whole cloud but not much farther. I've adjusted your cam2.

3. careful that the reset rate of your dual rest fields matches that of the sim (which is set to 50 frames in your case). I adjusted the shader's reset rate to match.

4. Your light wasn't casting shadows. I added depth map shadows to it.

HTH.

Thanks for this Mario, some good knowledge, gonna have to start consolidating all your posts about the pyro shader somewhere, so I can keep track of it!

[Jamel Drayton]

Hmmm 1 hour really I wish that was the case, It deff has somthing to do with me having an older computer. I went ahead and did a hires version any way surprisingly it didnt take as long like 9 hrs. But im not sure I like it, the highlights on the fire look odd for some reason.

Explosion_hiRes.zip

[mightcouldb1]

It looks like your highlights that could be higher than the value of 1 are being clamped for some reason. I would play around with your pyro shader and check out your value/noise remaps.

[lukeiamyourfather]

Yup. What I suspected: the attenuation method was set to "Real".

Try this (go to frame 33 or so):

Explosion4_bak1_mgm.hip

A few notes:

1. Note that for very homogeneous smoke/fire, you can get away with a very sparse point cloud. (i.e: instead of the recommended 10*stepsize, you can go higher). In this attachment, I've set it to 100*stepsize and you get similar results for cheaper.

2. The pointcloud camera doesn't need to be miles away -- just far enough to capture the whole cloud but not much farther. I've adjusted your cam2.

3. careful that the reset rate of your dual rest fields matches that of the sim (which is set to 50 frames in your case). I adjusted the shader's reset rate to match.

4. Your light wasn't casting shadows. I added depth map shadows to it.

HTH.

There's some great information in this thread. Also I just found out the volume step size in the Mantra driver properties has a tremendous impact on the render times of Pyro FX. The default of .1 seems way to small for most scenes and will really make it run like a dog. Cheers!