New User - Pyro issues.

[Jim M]

Firstly Hello!

Quick intro ... I'm new to Houdini (like it) & have 10 years experience in the CG industry.

I have spent a couple of days looking at the Pyro stuff, and though I have most of the basic workflow down, I am a bit confused (and tired).

I have watched a load of tutorials, largely for H10 I think, and I am getting some what appear to strange workflow issues.

Typical setup... Fan model rotating (static rigd body) distubing some billowy smoke...

Firstly I have all the LoRes and UpRes Bgeos saved to disk, and the nodes are set to read from disk.

1. When I press play on the timeline, it all starts to simulate. This is unexpected as I am loading from disk. (Perhaps it is simulating the Static Rigid Bodys?). Do you have to play through once to load the files (and potentially extraneous RB sim) into a memory cache?

2. I am having IPR/caching issues... If I am doing an IPR mantra render, and I click to a different frame, even if I have played through the timeline once and made sure everything is Simulated/Loaded from disk, it jumps attempts to simulate for ages and then renders the lighting out diffently/i.e totally wrong... or just goes a bit mental.

3. I am confused as to the display flags. I watched a tutorial where the guy flipped between the upres and lores in OGL and the upres detail was great. The difference was obvious. No matter what I set Render Display flags to, I cant get the behaviour where I can flip between the two. I can render out fine, or I can set it to look great in the veiwport, but I cant flip between the upres and lores..... With the sim-switch set to upres, the lores visualisation is errored (within the geometry node) or chevroned/greyed out or whatever you call it, I dont understand why. Should I set the sim-switch to both? I thought it was because I had pinned my veiwport in a weird way or something, but its not that. Perhaps some object view switching setting i dont know about?

4. Occaisionally when happy with sim, uprezzed and all loaded in, I am happily in Shops adjusting shader parameters, then all of a sudden the IPR is displaying things as a flat density output, almost like an alpha (it did this with some Fireball sim, but only to the smoke). I think its getting confused. Just want to check to see if its a common issue or theres a common solution. I dont thinks its the shader/Material settings, as I have to restart the 'Simulation', even with load from file setup, to get the IPR to render properly. Occaisionaly I have had to delete the Material from SHOPS and reload it in/reapply to the object nodes to ensure its applied.

4b. Also had an issue with a saved Mantra sequence with one of the frames jumping suddenly, couldnt figure this one out at all, as it looks fine in OGL.

5. I read in the online help, before you upres, one is meant to turn off density visualisation. Why? (perhaps help is outdated?) I have seen 4 different tuts on Pyro and no one has done this, and it all works fine for them.

My main issue is certainly caching/loading from disk, naturally I dont want to be waiting for things unnecessarily, particularly if Ive already done my sim. I noticed and attepmted to change the cache settings on the Autodop network, but couldnt get the behaviour I am after. Also have seen people using Cache nodes to cache particle data, but this doesnt make sense to use as I am already loading from disk. Also seen people using file nodes to load particle caches and geometry caches, again probably not the answer.

I suspect the "caching" issues I am having are connected to the secondary issues.

So I am not having a totally smooth ride

Sorry for the long first post, and many thanks for any input.

Jim

For info,

H11

XP64

8 Core

8gb Ram

Quadro 3700

[Macha]

1.

At the bottom right of you screen is a button that disables simulation. Try if that helps. Perhaps you are in the wrong context and it simulates, or have changed something, or the (zipped bgeo) file is so heavy to load that it looks like its simulating. Make sure you enabled Load From Disk.

2.

see 1 (?)

3.

You may not have simulated or cached or saved the hires yet. If you have, dive into the node and see if there is a display flag on another node.

4.

Don't know. Shader is attached? Pointed to correct geometry?

4b.

I noticed that some users, inlcuding myself, have had this problem. There's apparently a workaround for this but I forgot where in the posts it is burried.

5.

Perhaps because displaying uses resources? I could imagine that happening on very large sims.

I think your main problems are related to saving loading and caching the right thing. It's a bit tricky to see through that at first as there are many variables to take into account.

Good luck! It's fun when it works!

Edited August 14, 2010 by Macha

[Jim M]

I think your main problems are related to saving loading and caching the right thing. It's a bit tricky to see through that at first as there are many variables to take into account.

Hi Macha, Thanks for the quick reply. Appreciated.

I just tried setting the display AND render flags to 'All Fields' in the UpRes and 'PyroFields' in the LoRes. Turned off simulation and it now works a treat. I am so sure I tried this before amongst many combinations of scrabbling around in the dark. Sometimes when I go back to frame 1, it doesnt actually go back all the way back to frame 1 in OGL, so I imagine I might have tried it not realising the quirks of my setup, stability of the release etc.

Thank you for reminding me of the phrase 'wrong context', I seem to be spending alot of time there at the moment.

Ok I believe I nearly have the workflow I need.

My issue now I have all that working is to do with the Mantra IPR, bare with me here...

My files are all loading from disk fine, this is evidenced in the scene view as I can scrub the timeline with a big sim looking at the upres in OGL. Its fast and responsive. No stuttering. No simulating. Fantastic.

I go to the 'Render View' to look at a few frames and see how it developes with an IPR. First one renders fine. I stop the render (or dont), and move along the time line, now it trys to cook from the frame I was to the frame I moved (or perhaps even trys to cook the whole sim).

This isnt a massive issue as I can go back to the scene view, scrub to where I want to be, go back to the Render View, then start the IPR again.

Inconvenient it is though. Any thoughts on that? Does it work like this for you? The material shader is a post process right? rather than feeding back info to the sim?

J

[EDIT] as a further bit of diagnostic info... If I delete the AutoDop (turning off autosim on the Autodop node does nothing), and render it no longer simulates when I am in the Renderview. It does some weird stuff where the shader isnt refreshed (in fact it might be the shadowmap, which incidentally I havent cached, its just the default temp), but if I hit refresh on the IPR it works. So I think theres two things happening (maybe only one actually), 1. My setup is slightly wrong 2. Its a bit buggy, which is alway frustrating as a new user, particularly with a deep program.

Getting there !!!!

[EDIT 2]

Workaround found.

with my RBD oobjects, set render/disp flags to last node before DopExport... Doh!! This silly mistake was frustrating me for ages while I couldnt get the same behaviour as in the tutorial I was following. Live and learn indeed. That said, with simulation switched off IPR shouldnt be triggering the autodop.... !?

....I believe it is a problem with IPR triggering things it shouldnt, and not realising it need to refresh Depth shadow maps when the frame changes. If I stop the render, and move its fine, no scrubbing (I guess I am used to fast IPRs). To be fair I am entirely impressed with the IPRs speed when it goes good, setting the timings in IPR and sampling in Mantra node really makes a massive diference... I am getting render speeds for volumes which are almost unbelievable.

Just thought I would write this stuff down just incase anyone has similar issues/confusion.

Out

Edited August 14, 2010 by Jim M