Crashing

[Renderhouse]

hi, my houdini is crashing as i am doing this scene, i just low it down to 40 frames bcz earlier it was crashing after 40, moreover i have cached it and when i read it in file node and play it starts recalculating again and when it comes to 36 it gets crashed? can anyone help me out in this?i am beginner in houdini  

my pc specs:

16gb ram

amd ryzen5 2600

2tbhdd+ 256gb ssd

1060 gpu

[underscoreus]

It's going to be a bit tricky to pinpoint the exact cause of your crash without an error message or the hipfile itself so I'll just be going over some general things below.

• System resources: Like I said I can't know for sure what the issue is but 16GB of RAM is not a lot. For an RBD sim it should probably be enough but when you could do is to open a system monitor like "task manager" on windows, "Activity Monitor" on mac or "htop" on Linux and check it while your sim is running. The main thing to look at would be the RAM usage. If the RAM usage climbs to the maximum amount then Houdini is prone to crashing since the sim tries to store all the data inside RAM and then write it to disk and if it can't fit it in the RAM it will try to store some of it in a temporary location on your main drive, however when it does this Houdini is very prone to crashing since this is a lot slower than just storing stuff in RAM.
• When it comes to reading your cache back make sure you have the "Load from disk" option checked. Again since I don't have the hipfile I don't know if you are using a "file cache" node or something else like a "dopIO" node. But it should be called the same on any node that supports it. If you are using a straight-up "file" node it should not be an issue since a "file" node can only read from disk. If that is the case just make sure that the "file" node has the display flag on it.

[Renderhouse]

i am saving it in output node, save to disk option, then i use file node and use read but nothing works well, sometimes i use plaback button on dop network to see, but thats not fast , so should i use file cahe? and how to use that, and i have a hip file i am getting one more problem, i added two fractures in this building one is vornoi and other boolean, and want them to work together but whats happening i merged them, and make it one and did a sim in dop, and vornoi and bollean is working , but the building that wasnt fractured in boolean still stands whereas i put vornoi there to crack them, but thats working like two layers, this is my hip file 

buildbreaking.hip

[underscoreus]

@Renderhouse Nice, I can have a look at the hipfile, however, do you think you could either include the building fbx file or just check the "lock geometry" button on the file node reading in the building geometry (Snowflake icon button when hovering over a node. If you save the scene after checking this button it will save the fbx into the hipfile itself)? 

[Renderhouse]

thanks for the tip, there u go sir, 

buildbreaking.hip

[Renderhouse]

if that wont work, here is the fbx

buildings fbx.fbx

[underscoreus]

Alright, I had a look at your hipfile and I came up with some examples on how to better utilize the Voronoi fracture node, how to use the file cache node, and preventing there being two of the same building in your RBD sim.
I have come up with a solution on how to combine the Voronoi and boolean fractures so they both work on the same building, however, this is not a very good solution as it is very slow and doing boolean operations like this is VERY prone to causing bugs and issues. Boolean fracturing is not a very stable way of doing things, especially when your geometry starts getting complicated.

I'd recommend having a look at a tutorial/tutorial series on RBD sims and fracturing to get a more detailed explanation of everything and how it works, but just as a quick rundown of what I did:
Instead of using spheres for the Voronoi fracture, I use point clusters that are then rayed to the geometry. The Voronoi fracture node only uses points, not geo like the boolean fracture so my go-to is to use the "point replicate" sop and then if needed use a "ray" with "minimum distance" enabled, then shove that into the Voronoi fracture node.
To get the boolean working I add a for loop to run over every piece we get from the voronoi fracture and then only boolean the geometry that is near the piece we are currently iterating over. Blasting the other geometry is simple to save cook time on the boolean fracture node since it is slow and we need to cook that node 2000 times with this method. Like I said above, not a very good method but I'm not really sure of another, better, method. I choose not to hook up this to the RBD sim since it is so unstable and often gives bad geometry, so in the hip I've only connected the voronoi fractured tower.
In the dopnet I haven't changed much, just rearranged some of the nodes based on my personal preference and removed one of the two RBDPackedObject nodes since you're only supposed to have one, unless you have multiple buildings etc.
After the dopnet I just placed down a dopIO and a filecache node since I could not see any file node in the file for reading in the geometry from the sim. To cache the sim, simply just use the file cache node here at the bottom of the node tree.

Hope it helps, good luck!

buildbreaking_mnb.hiplc

[Renderhouse]

thanks for the help sir, i used two fractures bcz, i was kinda faking debris with vornoi and with boolean i was extracting big chunks of building from it, but i see the file u sent me, that looks like breaking uniformly, i am not getting a little debris type stuff, i think there is other way of making layers things stuff , like debris,dust smoke right?, i  didnt get for each begin and end, can i get any tutorials about all the basics out there or i need to read it on side fx, and how its playing too smoothly? this is my first experience with smooth playback, i dont know, how to do that, and for cache i just need to put dop import and file cache, and need to do what , need to select something in file cache?  i am a noob

[underscoreus]

There are a lot of resources out there, some paid, some free.
Most of them are probably listed somewhere here: https://forums.odforce.net/forum/66-education/

However, the tutorial series that I have recommended before is either this one, "Houdini is not scary".
Or, the ones in this playlist, however they are somewhat more fast-paced, "SideFX Houdini For Absolute Beginners".

Both of these have videos in the same playlist where they start talking about RBD sims, however, it might be a good idea to find tutorials specifically for this topic as they might be better suited for that. Learning Houdini is going to be a step-wise process of encountering a problem or process you haven't done before and looking for a tutorial on how to overcome that problem or a tutorial to learn that process. I don't think there are very many online courses that have it all in one. Though maybe someone with better knowledge on the tutorial landscape out there can correct me on that.

As for an explanation of the specifics you are mentioning in the hipfile I sent you;

• If you want a greater contrast between the smallest and largest pieces you can either turn down the "scale" parameter in the "point replicate" node which should give you pockets of smaller pieces or you could use a good old trusted technique where after you first fracture your pieces with a Voronoi fracture you fracture some of the pieces again inside a for loop. This is going to be a somewhat slower process since for-loops are pretty slow, but if you've got to do it you've got to do it. Either that or have a look at constraints like mentioned in this video by Steven Knipping
• Yes, you are right, in FX we usually have multiple layers of FX to get the final result, one layer is the RBD sim of the building collapsing and from that, we make debris/grains sims for the small crunchy details as well as another sim for smoke/dust clouds.
• The "for each begin" and "for each end" are what make up a for-loop (or a for-each loop) in Houdini. To simplify the explanation of what it is it allows you to execute every node that is between the for each begin node and the for each end node x amount of times. Where x is determined by the user, it could be a certain number you choose or in the case of that hipfile I sent you, x is the number of pieces that we get from the Voronoi fracture node. This is a very simplified explanation skipping a lot of the technical stuff but I don't think I can write up a good enough paragraph about it here to cover everything.
• As for the playback speed that all has to do with what nodes and what settings you set on the nodes as well as in what order you place nodes. It's all about optimizing your node tree so that Houdini has to do the least amount of work possible which means that you get a faster and more responsive scene in return. I don't think I optimized your scene that much, I think the main gain is coming from there not being two buildings that were stuck inside each other inside your rbd sim as well as using points rayed to the surface of your building instead of the mountained spheres you were using before for your Voronoi fracture. My rule of thumb with voronoi is that if it takes more than 10-15 seconds to compute, something is wrong. The voronoi algorithm is very optimized and very fast, so unless you have a crazy high-res geo or you are trying to make hundreds of thousands of pieces it should go very fast to fracture using voronoi.
• To use the "filecache" nodes simply click the "save to disk" button inside the node and it will cook the sim and save out the result to your disk, and as long as "load from disk" is checked it will read the cache from disk when you playback instead of trying to cook the simulation again. Just note that if you ever make changes to your sim you'll have to "save to disk" again to see the updates when looking at the "filecache" node in the viewport.

[Renderhouse]

ok, thanku soo much, this really helped me alot, 

https://imgur.com/a/31yqRF8

https://imgur.com/a/RhmdWaa

i made this btw, hope gonna learn soon about everything, which is not just productive but efficient too

r u on discord?

thanks 

Edited April 3, 2021 by Renderhouse

[underscoreus]

Looks good! Glad you've got it working.

I mostly only deal with Houdini on the forum here and maybe some on the Houdini artist Facebook group. Leaving discord for casual chat with friends etc.

[Renderhouse]

Ok thanku soo much, can i write again in this chat, to ask questions?

[underscoreus]

I'd recommend you check the forum if others have asked similar questions to what you'd want to ask before and had them answered, and if not, make new topics for any other questions to keep everything as organized on the forum as possible.