Initial. State. Again.

[TomGore]

Hello, I have a problem with starting a sim with Initial State. After simulating smoking fire to frame 318 where it is high enough, I get back to frame 0. Then I click Load and Start, I pick up my last frame file "wtc-fire-test-spd_318.aur" and it starts from scratch again instead from frame 318 state. Could you please explain me step by step how to do an initial state? I think a dedicated separate button would be good to make it as simple as possible (like in fume fx or real flow).
I've tried with restore instead of Load and Start, but no joy. Even if set up a restore frame every single file. It starts from frame zero and starts simulating from scratch.

The other thing is - as a customer I have no access to the main Phoenix forum (only Public section). Can you assign my TomGore account to be able to do that?

Version 3.05.02
nl

[LarsSonparsson]

You need to set the simulation to start from frame 318 in simulation rollout.

[Svetlin.Nikolov]

Hey,

You need to drop a mail to support@chaosgroup.com for the permissions. Please check the docs on Load and Restore though When you restore, you need to scroll the timeline to the frame from which you want your simulation to continue. Lasse's note on the Load is the other way to do it, but I think you need just Restore if you just want the sim to continue from where you left off.

Cheers!

[TomGore]

...and then hit restore or Load&Save?

Something different came into my sight: Please check if smoke emitted directly from fuel (Enable burning/Smoke Amount) cannot get RGB color information thus can't be colored with bitmap. Only smoke generated by Source can carry colors with uvw channel. In case of fuel-smoke, only first frame of bitmap is visible in preview and then RGB values dissappear (in standard, non-gpu preview). Please check if this is a bug or my scene only.

best

[TomGore]

Svetlin, I've read docs thousands of times. But what I need is to start scene with smoke already high from frame zero without having to wait -200 frames until it reaches the correct position. So it is not a standard restore situation.

[TomGore]

After entering frame 318 as start, after selecting file _318.aur and clicking Load&Start, the simulator starts sim from the scratch at frame 318. I am almost sure there is a bug. Load & Start doesnt work as it should - it forces phoenix to start from file _000.aur. I can attach the scene but it contains some xmesh cached geo and so on.

[Svetlin.Nikolov]

Yup, that's the way to do it - set start frame to 318, Load & Start the cache you need at that frame and the sim would start from there.

There are two things that could go wrong:
- If you pick a cache which does not have velocity, the simulation will start frozen and would start moving only where there are sources or obstacles affecting it. If you load a frame with velocity, then everything should continue to move normally.
- If you use adaptive grid or in general - if the cache is not the same size as the grid - then the loaded cache would be squashed or stretched to the grid size of the simulator.

If I remember correctly, you wanted to rewind back to Phoenix 3.04 - I have to check the changelog, but there would be at least 2 issues there - caches of different sizes won't be stretched to the grid size and FLIP sims won't be loaded unless the cache is a backup frame.

What happens to the RGB is expected - the burning is a separate process from the source emission, so the source cannot influence it, at least because it might occur at a distance. By default the RGB in the grid is black and in the latest nightlies there is an option in the Dynamics rollout which allows you to change that default. If you need non-uniform color, you could use the Mapper or a source in Brush mode to color fluid in a particular volume of the sim.

[Gosho.Genchev]

Hey, Tom, unfortunately I can't reproduce either of those issues.
The Load & Start option correctly loads the specified files and begins the simulation at the frame specified as Start Frame.

I checked the Smoke/RGB issue you've mentioned as well, and things seem to work as expected. Once the smoke reaches the RGB source, the RGB channel is carried by the smoke.
I assume that the issue you're mentioning is the fact that the RGB channel is not propagated through the container when no smoke is present - that is indeed the case. Maybe Svetlin.Nikolov can clarify if this is the expected behavior.

I'm attaching a screenshot and the RGB scene just in case.

load-and-start.zip

[Svetlin.Nikolov]

Yup, the RGB issue is expected, but we have to figure out why Load & Start won't work as expected even with 3.05.02.

TomGore, here is what I'm doing to Load a frame from a smoke sim further down the timeline: load and start.zip Do your steps differ from the second Load where I pick the Backup Frame?

[TomGore]

I will check it again. The only difference is I use adaptive grid and some collision object. Smoke is emited from a texture mapped animated box (very simplified collapsing building) with masked fuel/smoke. I use 3.05.02.

[TomGore]

I did exactly the same sequence and it restarts sim from scratch. Only difference is I've started sim at -400, then stopped at frame -271 (when smoke was high enough). Then set up frame 0 as starting point, 1000 as ending frame. Loaded and Started with frame -271 .aur file (It is designated as backup frame) and it started from frame -400 from scratch, (like standard start button from the beggining).

[TomGore]

Okay, did the same with adaptive grid off and it worked well. So now please try the same approach by yourself with adaptive grid (Smoke, 0,001, extra margin 10). And perhaps some collision object for similar situation. It seems in my case adaptive grid is the problem. Which sucks, because it means unwanted terabytes and hours of longer simulation (imagine this kind of smoke from attached picture; without adaptive grid and without initial state)

[Svetlin.Nikolov]

Ohhh, I get it - is your starting frame in this case set to 0? If either start or end frame is set to 0, this it's a special value that means to use whatever the timeline's start or end frame is - if you set it to -1 or 1 it should be okay.

I really don't like these special values some parameters take and it's time to fix this because it bugs me as well...

[TomGore]

I really think there should be an "initial state" button that does exactly what it means - it could also be a scripted in a way that prevents to apply initial state to adaptive grid or to frame zero. I think it's not rare when someone starts initial state from frame 0 which is a default 3dsmax first frame

[Svetlin.Nikolov]

Yup, gotta rework both the start/end frames and will think about how to make the initial state more intuitive.

Cheers!