is there any way to blur an HDR env image before the rendering with different values of blurring per object in order to reduce the rendering time? I have been told that there is a special blurring process for hdri images but I don't have more info about this.

I kinda fixed it, if you change the solver from bullet to RBD just for the debris, you cant really see the problem. There is much less scaling when they hit the ground, if there is any, but because they rotating, it seems like part of the rotation.

But still will be nice if anyone ever come with a solution or explenation why bullet creates this problem.

Finally, I just realized that changing the fps, only effects simulations with bullet solver, it works fine with RBD solver. I hope in a fix for this from SESI.

zdimaria
The real solution imho to this would be to up your frame rate. Changing your FPS to something lik 1000 or 2000 will allow you to keep the simulation the same, and then slow it down to ultra slow motion afterwords. (This is how they would have shot the scene in Inception)

well I tried every possible way to have the slow motion but by increasing the pfs change the simulation, it does not just slow it down. It like there is no gravity at all, for example in the this file the torus will never touch the ground, all the pieces fling around, the same with debris, its out of control. The same is with the scale time parameter, it changes the simulation. Only timeblend-timeshoft SOPs or CHOPs can do it right. That's why I want to get a simulation to looks real and then slow it down. Also I will save simulation time.

zdimaria
Actually I think I know why an isolated piece is strobing when it hits the ground. Your simmed geo is spinning chaotically from frame to frame. When it tries to interpolate from each of those positions it strobes.

If you increase the rotational stiffness of the debris to 100, and set collision padding to 0, it helps alot. This isn't a problem with the timeblend timewarp setup, just the sim.

where is collision padding parameter? If is not problem of the timeblend timewarp setup, then why by disabling them it goes fine? Its odd…

UPDATE:
I fount padding, but it does not fix anything. Do I have to use something else in the SOP level before the retime setup?

zdimaria
Not yet. The strobing is strange to me –it seems like they remain the same shape just scale down through the interpolation. I'll keep looking at it though. Although I would still like to figure this out, is there a reason you can't change your sim to give you the results you want, instead of fixing it after?

is quite complex simulation with hundreds of pieces. It is something like the Paris scene in the Insception but all CG (in the movie was not). The physics should look real but also sureal, like being underwater. I am already using a lot of masks with forces like drag to slow them down and push them around. But at the top of that I want it to run for 2 seconds and then gradually slow down and keep going like this few more seconds and then come back to simulation's original time.

I use a VOP with ramp which remaps the time of the animation.
I don't want just to slow down all the simulation as the example file.

Also it is much easier to fix the final artistic look of the time with this way and avoid resimulate everything again and again. So far it works with the main fractured pieces because they don't change over time and works with fluids (dust and liquids). It doesn't works with debris as you can see.

thanks you for looking on this.

Is there any way to get position and value of current point in a float ramp?

I would like to convert these values to frames and display them using Label parameter on my DA.

I know you can get position and value of any point by using its number but I want the current selected point which is displayed on the Point No. parameter on the ramp.

any luck?

zdimaria, here is the example file which I fotgot to include with the other examples. As you can see the maingeo has no problem to retime, the same retime nodes applied to the debris creates a strobing on the animation.

zdimaria
Just opened your file. the NEW_GEO_OVERTIME problem can be fixed by rearranging your nodes.. Because you are already creating an id attribute on the particles, and the timeblend is set to look for that attribute, if you just copy your spheres after the timeblend all works well. So, it should go popnet1 feeds into timeblend1 feeds into timeshift1 feeds into copy2.


Is this solution viable for you project?


Ill look at the other errors in a bit.

zak

well I am afraid is not, the method in example file was just the way to test the debris using particles collision. But the method that I am actually using (as I descripted above) uses POPs only to get the intial velocity but all the simulation happens inside the DOPs. I can't have the slowmotion before the instancing. I will attached a file with this method when i will be home in an hour.

cheers

zdimaria
I can't open your file right now, but if you really want to use a timeblend to smooth out the strobing on geo with changing points, you can try adding an id attribute to the points. This wont work with skinned surfaces but with a flip sim or with particles it should work to some degree. When a new point is created you need to add a unique id attribute to it, so that the timeblend has something to follow.

I haven't had a chance to try this out, but when I have a minute I will put together a hip file for you.

I have managed to retime almost everything with one or the other way, but this is the only I am missing reading bgeo sequence where new geometry are coming is over time.

The problem is that my method of creating debris uses the velocity of the pieces of the fractured geometry and emmits particles from the interior faces which has vel>5. Every frame new particles are created and using a copy SOP I create unique instances of debris to each particles and pass them to dynamics. In the particles network I use a kill POP, so once the particles will pass from POPs to SOPs to DOPs they will be killed. Can we have this attribute ID on the SOP level in order to be attached to each instance of debris before they go to DOPs? I really hope what I am saying make sense to you.

I hope for your idea to work, it will save project. I will wait your example hip. Thanks for all your help.

any tips for outdoor render with PBR which use hdri lighting ?

CeeGee
Volcano preset

Thanks jlait and Coen.

Sim details:

division sizes - 0.02
voxel counts (frame 200) - 160mil
simtime - 5h 40min
rendertime - 22h 30min

did you used autoresized container with your slow motion effect at the end of your sim? How you did the slow motion, timeblend+timeshift SOP, CHOPs or VOPs, can you please share few details about this?

Loudsubs
Would I want to break up the vel into 3 scalar volumes using your exact same method? or do I want to create a vector volume to copy the volume mix with? I created both setups in your file.

I guess this is just a test setup but if not, in your method 1, you have blast 3 times the vel_x and forgot vel_y and vel_z.

I have attached a scene with all possible simulations and there notes if there is any error.

Seems that you can retime either using CHOPs or Timeblend+Timeshift SOPs any kind of simulation (RBD, particles, fluids) but with few exceptions.
When auto-resized container is used by the fluid simulation there is a strobing, Jeff gave a solution to that above.
When you retime FLIP fluids there also a jittering, zdimaria above gave the solution, the reseeding should be turned off.

But when new geometry or points is enters the simulation over time, there is a problem. Here is the example I used above: I created a system for my project which generates debris from fractured geometry, the amount of debris changes over time, as more fracturing there is, more debris will born. But here I have the same problem with the reseeding, when I am reading the bgeo sequence from disk with the debris simulation, the timeblend creates the strobing, when is turned of I have no linear blend between frames.

All the above you can find them inside the attached hip.

zdimaria

FLIP FLUIDS
Also it seems nothing works with FLIP fluids simulation, neither Timeblend - Timeshift SOP or CHOPs, there is some strobing on the particles (the size of the container is constant), I tried to use it before and after the meshing.

There is no reason the timeshift sop wouldn't work with flips, or any geo for that matter. The timeblend however, will probably not work because you probably have reseeding enabled on your flip solver. This changes the number of particles over time, and the timeblend relies on using a consistent number of points to work. This also means that using it on a meshed surface will also not work. If reseeding is turned off, however, the timeblend timeshift method should work just fine.

zak

well, I tried it also to retime a simple popnetwork and I have the same problem. Also I cant find the reseeding parameter on the FLIP object or solver. I will create an example scene and post it in an minute.

UPDATE
ok I found reseeding parm on the flip solver and it fixed the problem by disabling it. So I cant retime a particles simulation which generates new particles over time?

UPDATE2
as you said the timeblend creates all the problems but if I will turn off reseeding to fix the FLIP fluid. What can I do in the following: I created a system for my project which generates debris from fractured geometry, the amount of debris changes over time, as more fracturing there is, more debris will born. But here I have the same problem with the reseeding, when I am reading the bgeo sequence from disk with the debris simulation, the timeblend creates the strobing, when is turned of I have no linear blend between frames. Is there any solution for this?

another one, the world seems to be rotated 45degrees right, you can see that by the viewport grid and how the default camera rotates. Once you restart another session everything is ok but I saved the scene this time and you can see it yourself.

Houdini11.0.581, Linux64, Education Edition

jeff
I would give the Timeblend - Timeshift SOP combo another try. It should do a linear blend between the two volume primitives.

If you have dynamic resizing of containers on in the Pyro simulation, you will definitely see strobing and pulsing due to the volume primitives changing dimensions.

One way to keep resizing post-sim is to use a new Volume SOP set to pick up the final container settings from the Pyro Object and then use a Volume Mix to copy the dynamic container in to the new container.

This is a linear interpolation so you will start to see the hits at whole frames at about a 5 to 6 times slowdown.

See the example file.

Note that you will need to do a Volume SOP and volume Mix for each volume primitive you want to re-time.

Btw repopulating your high res sim in to lower res volume containers with this technique is something that you should know. You can set the Volume SOP to be a frustum based volume from the current render camera as well.

PYRO
Jeff this method works great. But when I use explosion for example from the pyrofx shelf the fire part missing from the rendering and is everything like a smoke. I thought that may the blast be responsible for that by deleting temperature and heat which are used by the shader but even by disabling blast, I get the same result.

FLIP FLUIDS
Also it seems nothing works with FLIP fluids simulation, neither Timeblend - Timeshift SOP or CHOPs, there is some strobing on the particles (the size of the container is constant), I tried to use it before and after the meshing.

jeff
I would give the Timeblend - Timeshift SOP combo another try.

thanks for the reply and the file Jeff, I will give it a try now. Is this works with FLIP simulation? CHOPs it doesn't, I tried it.

zdimaria
1. You can resample the channels in chops and reduce their detail.

2. Not really sure I understand.

3. Try adjusting the timescale parameter on the Simulation tab of the pyro solver.


sorry its not much. hopefully enough to dig around a bit until you get better answers

thanks for the reply zdimaria

1. I tried resamle already but does not make much of deference on the delay because either way you have to load the original geometry and loosing details of the animation.

3. I am afraid you are right, I did few test with FLIP and pyro and only timescale works but as usual effects the look of the simulation

2. Now I use stretch and I scale up or down the whole simulation. But lets say you want to start with normal speed, then gradually slow down and keep it for few frames and then return to normal speed. I hope this makes more sense.

I did few test in order to find the best way to retime RBD simulation: increasing fps or decrease scale time on the dopnet node gives the look of slow motion but screw the all forces and you and up with a very weird simulation. Then I tried timeshift SOP which gives gaps on the animation with paused frames. The best way seems to be using CHOPS, you import the animated geo and scale as you want. Now I have few questions:

1. There are too much details when you bring the geometry to CHOPS and I have to wait 2 minutes to load the curves and keep closed the Motion View, otherwise it will keep freezing in every change. The good this is that once you load it the animation goes fast but is there anyway to avoid this delay?

2. So far I use the simple stretch node to retime the simulation, is there anyway to give different values to different areas of the simulation and all of them to be attached and keep running as one piece?

3. Is there anyway to retime fluid simulations, like smoke and liquids? I tried to retime with CHOPs a pyrofx fireball simulation but without success.


thanks in advance for any help or info.