Shadow Map Turning off and on between frames

[lxdengar]

Hi all,

I'm running an intense set of Smoke sims on a XP64, Max9-64 workstation. The render memory footprint of the sims is high (5.5 GB), but no where near the record, or the limitations of the box I'm rendering on. Overall the sims are working fine.

However, for a couple of the frames, it appears one of the shadows is not getting calculated. Portions of one sim get lit for a frame, and then go back to being in shadow on the next frame. The shadows are being cast by another fume box, roughly in the same space.

I'm attempting to track down how to fix this. I've tried lowering the illumination Map's undersampling threshold, but with no results. What other tips/tricks should I be trying here?

Here's an example of what I'm talking about.

[Rif]

are you using MS ?

your casting shadows from another Fume grid your saying ? or just a box ?

[lxdengar]

MS? Matte/Shadow?

Nope, no other objects in the scene except the fume boxes. Essentially I have two fume boxes roughly in the same place with different sims. Both have cast and receive shadows turned on.

In the example JPG, the light in question is behind that smoke and toward screen right. To me, it looks like the grid further 'back' in the scene is not properly casting shadows to the foreground one, but only for that frame.

I can't help but wonder if I'm running into some sort of limitation here.

(edited for clarity)

[Rif]

No Ms means Multi scattering.. are you only using IM ( illumination map ) ? or you have both MS and Im on ?

[lxdengar]

No multi, just IM. Should I try one with it on?

[Rif]

nop nop .. MS sometime can be doing that on low ram rendering..

so your farm that your rendering that on is actually having enough ram ? all the machines ?

what if you render locally that frame that it turns off on , does it fixes it ? i v had the issue before where the IM dosnt compute properly if the machines rendering it dosnt have proper ram ( x64 ) ..

You also have to remember that in Fumefx 1x .. having multiple Grid on render will Add both grid ram usage on top of the other on the rendering machine.. so if for example each grid takes 5 gig of ram to render , both grid together will use at least 10 gig to render properly..

[lxdengar]

That's what I thought. This is a local render, scanline. The ram usage is total for the sims, not per sim, unfortunately. The box has 10GB available, so we have plenty of ram here.

I'm assuming I can trust the max render window and XP's task manager to give me an accurate memory usage statistic.

This is actually happening from two different lights (RGB lighting) on different frames. I've tried it on different boxes, with the same results.

[lxdengar]

After a lot of trial and error, I found something that's working, but I have NO idea why.

Essentially, I'm re-rendering the frame BEFORE the bad shadow frame, along with the bad frame - and low and behold, the previous bad frame is fine!

But the frame BEFORE is now missing the shadow! I know that sounds a tad odd, but I tried it 3 times on 3 different boxes, with the same results.

Anyway, its fine now. I'm re-rendering the bad frames to a different sequence name, and replacing the bad frames from the original sequence. However, I'd sure like to know what's going on here.

[Rif]

hum.. weard !!

If you can , please send us the file and ill test it over here when i have a sec .. you can also cc mailtoupport@afterworks.com
you can send it to me as well at mailto:rdagher@rifaatdagher.com

[sitnisati]

It might be that you're out of memory as I don't see other reasons at the moment.
Does this happens on the same frame and on the same machine all the time ?
If so, maybe you could see what happens there.

Kresimir

[lxdengar]

It was happening on the same frames on 4 different machines (identical configuration).

Total memory footprint from max was ~5564 MB. RAM free was nearly 3 GB. Odd.

Doing more tests see to show that the first frame of a frame batch has this problem(i.e, render 5 frames, the first one will be wrong).

[ChrisMoss]

I'm having the same problem. Back in Fume 1.0a, the first frame rendered on a machine would do what you are describing. So when I sent a job to the farm, I would always have to re-render the first series of images. A pain in the ass, but still doable. Now in 1.1, the problem has gotten worse. The shadows being casted on other fume objects will not show up if the camera is too close. So flying through moving smoke composed of different fume grids has now become impossible without the shadow maps turning off. I really don't think it is a ram issue either as all of my machines have 8 gigs and the scene is very modest.

[Rif]

hum.. well the ONLY time i have Ever seen a flick on the IM ( illumination map) is with testing those 2 cases :

a) trying to bypass the fumefx versions with non real versions .

b) missing some ram on some farm..

I have never had any issues with the original dlls ..

so i m sorry cant help more than this really .. but it looks weard to me..

[lxdengar]

Rif, you know I'm legit.

I can't send this scene where I have the issue due to NDA, but its a pretty easy sim to recreate. ~5.5 GB of ram, 3 lights, each with 2k atmo shadow maps, 16 samples. Bunch of space warps keeping it a tornado shape. Its a very close, highly detailed sim. I'm not running out of RAM. We've tried this on a 18 GB box.

Mike

[Rif]

I know Mike i know you are , i m just saying what i remarked.. obviusly their must be something weard creating this, but i never ever saw this happening in my setups .. so i m really confused on this issue

i wish i could help more than this thats why i m kind of unhappy .. i would love to run some tests but i m more than overloaded right now..

[ChrisMoss]

Here > http://www.3dmoss.com/Fume%20Flicker.rar is my file demonstrating the problem. Its 3 clouds lit by 3 lights. Each cloud needs to be simmed to frame 8. If you then render a sequence from frame 8 you will notice the first frame rendered on a computer will not render the shadow on the middle cloud. Or you can render frame 8, then render the region of the middle cloud, and the shadow will appear. Maybe it is a memory management issue since the shadow appears when a smaller region is rendered?