Hey, great thinking! I'll give this a try. Thank you.

Alternatively, would anyone know another option to use the RBD Material Fracture node on multiple object parts individually?

npetit
Instead of an attrib copy SOP, use an attrib reorient SOP, plug the static mesh in the second input, and set v as vector attrib.

This didn't quite work for me. It was somewhat there, but some of the vectors were not exactly copying correctly from the original source.

A very helpful user named islamoos over on ODforce helped me find a working solution.

.hip file attached if anyone else is after a similar thing.

Crosspost from Odforce, as this one is proving difficult!

I have two objects. A static object I'm creating velocity vectors on, and a duplicate / animated version of the first object.

I'm trying to copy velocity vectors from the static object onto the duplicate animated object, but the point rotations are not accounted for. The copied velocity vectors keep pointing in the original directions.

How can I transfer the animated velocity vectors from the static hair curves onto the now animated vellum hair curves?

.hip file attached

Hi thanks for this npetit

If I try your first example of packing the volume before animation, then on the sop import set the packed primitives to create xforms, the volume does not render at all.

However your second example of adding the point velocity surface attribute to the volume does work.

I'll translate some of what I've learnt here into my problematic scene file. It's a little more complex than what we have in this simplified example here, but this is helping me get my head around what might be required.

Hello! I have a smoke volume and render camera, both travelling in the positive X direction at the same speed.


In this situation, I would expect to see only the background being motion blurred as it moves past the camera.
However, the smoke volume is also being motion blurred.


This is my Solaris / Karma setup (.hip also attached)


I have tried many different setups, but just can't work out how to resolve this.
Note: I'm using Houdini 19.0.531 due to work version restrictions. Is this the problem? Is there a way around this issue?

I have a pyro setup that uses two smoke density volumes.

I'd like only one of those volumes to receive secondary emission rays from an invisible piece of geometry emitting light from it's material.

I can see how I'd do this using regular lights, but how can I make this possible when using geometry as an emission light surface?
One thing to note is the emissive object has a camera projected texture applied to it. Does this make things even more difficult?

Hi zuoyuanle, I've seen this particular video before but there is no information on reseeding at all.

Hi mestela, you could right. I think I am just trying to load far too many different proxy files all at the same time and the proxy frame offset is causing it to search and load again on every framestep.

I will need to look into a different way of instancing these objects onto points.

I did try the instancefile method which was wonderously fast, but I could never get the randomised timeframe offset working with a looping sequence.

Hello, I have less than 2000 points (they're even cached and loading from disk!) but viewport playback is incredibly slow. The cache file is tiny at only 8mb.

These points have an instancefile sequence attribute playing through a proxy file sequence. Nothing else.

I have tried playback on a faster PC, and it does go faster, but on my main work PC this node playback is painfully slow.

What could be causing this to play down so slowly?

The performance monitor shows only one thing taking time:


Cache file of points to download if anyone is able to help out:
https://mega.nz/file/i1I3mYDC#z5UByCKeTmkLp7k9rMHhVKd9CwqUFffyJr4D6ovGt5w [mega.nz]

I actually ended up doing something slightly different to what I was initially going for here. Instead of starting with a random pile of vellum objects, I ended up going with a method that randomly spawns the low res vellum objects, then in the last step I transfer the low res dynamic animation back onto the high res geo.

I'm sorry I don't have time at the moment to fully explain my process (and I have certainly forgotten how this all came together), but I will attach my file that works fine for me. You will have to step through from step 1-6 and re-cache the parts you need to before running the sim.

I recall there is a second popnet during the process that is used to solely create the rest position for each newly spawned vellum object. I remember that part being the most difficult to get right, but I think I solved it with some help here from Vusta and some other helpful folk over on the OdForce forums.

This was built to randomly emit 20 or so different pieces of food, so you may want to cut this process down a little if it is too big.

The final result: https://youtu.be/fnsrkO3Sg90 [youtu.be]

Oh that's handy! I didn't realise the uv split seams sop had the promote to point attribute right there to use.

So I see this does separate the geometry at the uv border edges. How would you go about achieving this result without separating the geometry?

I tried a fuse after uv split seams, but it seems to revert back to it's un-split state again.

Hi Tamte, yes I was exporting from Houdini as an Alembic to bring into Maya.

I'm just testing this again now and you're correct, maya is reading the uv vertex attribute. I don't know what was going wrong for me before.

Although I no longer need to export the geo with a uv point attribute, I have also found a solution to the uvs being messed up when attribute promoting the vertex uvs to a point attribute - The problem was the vertices were still attached, so when promoting to point, they would cross over each other. The fix was to use a 'uv split seams' sop before the attribute promote.

Hi thanks Tanto, I learnt something today! I never realised you could create your own material networks!
I thought all materials should be created in the Mat context. I guess I could now have a Geo container called 'materials' with multiple material networks inside there.

Thanks!

Hi thanks for the replies. This clears things up and explains a few things for me.

My original issue was importing Houdini geometry into Maya, which was messing up the UVs. I initially thought the 3rd UV channel was breaking things, but later found out Maya will only read point UV attributes, not vertex uv attributes.

Unfortunately converting uvs from vertex to point messes up the uvs on the object. They don't transfer cleanly.

Anyway, thanks for clearing up the other stuff for me.

Hello, I'm looking for a way to help better organise all my materials in the Mat context.

I see I can create container nodes, with different materials inside, but those materials no longer show in the list when I'm selecting which material to use via a Material SOP.

Is there a way to group or organise materials in the Mat context, rather than just having hundreds of materials all in one massive grid or line?

By the way, what is the 3rd uv attribute for?

Why would a single vertex need more than two coordinates? I assume it only needs a u value and a v value.

What does the 3rd one even do?

I have 3 uv attributes on a mesh uv[0] uv[1] uv[2]
I would like to delete just uv[2]and keep the other two attributes.

I cannot work out how to delete just this one attribute.

I have tried using an Attribute Delete SOP set to uv.2, uv2 and uv[2]but it keeps saying it can't find the attribute to delete.

How can I go about deleting this one uv attribute?

Thanks for your help vusta, I'll take a look at this thread.

The orient transfer did the trick!

Just one crucial factor remains, and that is somehow creating independent class attributes when the objects are scattered - Furthermore the low and high res objects must have the same class.

Without these attributes, the point deform on the last step cannot differentiate between all the objects with the same class attribute name.


eg. a new and unique class name for different copies of objects:
High res box1 = class1 / low res box1 = class1
High res box2 = class2 / low res box2 = class2
High res torus1 = class3 / low res torus1 = class3
High res sphere1 = class4 / low res sphere1 = class4
High res cylinder1 = class5 / low res cylinder1 = class5
High res cylinder2 = class6 / low res cylinder2 = class6

This is certainly a tough one. I haven't looked into what is capable of the copy to points sop, but maybe there is a sort of attribute copy + add number feature?

Apologies not trying to sound ungrateful, it's just not the answer to my question at all I'm afraid.

Further down the line, the low res vellum must be able to use the class attribute on the objects to help deform the low res to the high res geometry.

I don't know what that file is you just uploaded either?