Context: I am a proficient Xgen user, though this is my first time grooming within Houdini.

Situation: I am grooming a geo head, and am lining-up a hairline, and doing so calls for cutting individual hairs/primitives. I utilize the GuideGroom node within the Hairgen node, and I cut my hairs. Looks fine.

I want to then move some guides, so I do, and my hairs don't move/update like normal. Auto Update is enabled as it updates when the GuideGroom node is not connected to my (node) tree, though it's halting any updates from being applied when connected.

I believe perhaps I'm connecting it incorrectly, so I am coming here to the forums to push me in the right direction. Is there a better way to do this and not have to re-cut all my hairs after a change I make?

There's an image of my... node tree... below? Is that what you guys call it? Thank you in advance.

valliay
Context: I am a proficient Xgen user, though this is my first time grooming within Houdini.

Situation: I am grooming a geo head, and am lining-up a hairline, and doing so calls for cutting individual hairs/primitives. I utilize the GuideGroom node within the Hairgen node, and I cut my hairs. Looks fine.

I want to then move some guides, so I do, and my hairs don't move/update like normal. Auto Update is enabled as it updates when the GuideGroom node is not connected to my (node) tree, though it's halting any updates from being applied when connected.

I believe perhaps I'm connecting it incorrectly, so I am coming here to the forums to push me in the right direction. Is there a better way to do this and not have to re-cut all my hairs after a change I make?

There's an image of my... node tree... below? Is that what you guys call it? Thank you in advance.

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Hey, the guide groom node isn't procedural. It stashes the input. If you make changes above it, you have to hit the clear button to re-cook the input (but then you lose all your work). Using the guidegroom in the hairgen node as the last node pretty much means changing anything else before in the hair or the guides won't affect anything after the guide groom.

It is not a good idea to use the Guidegroom SOP inside a Hairgen object node unfortunately. The place to use the Guidegroom SOP is in your object-level Guidegroom node, or wherever you create your guide curves. The Guidegroom SOP is destructive - it caches everything inside it, so it doesn't update when anything upstream changes. Anything that is similar to sculpting is inherently destructive.

To shorten the hairs along the hairline you probably want to shorten the guides in that region. You might have to plant extra guides in that region if you want to have a sharper transition between short and long hairs. Alternatively you could paint a mask on the skin for the region you want to shorten, and then use a Guide Process (Set Length). This could be used either on the guides or on the hairs.

Another option, if the hairs along the hairline are very different to the overall hairstyle (I'm thinking baby hairs) you might even find it easier to use a separate guidegroom and hairgen.

I'm sure this was a frustrating experience, but I am confident that once you wrap your head around the concept of doing all your destructive work on the guides (i.e. using the Guidegroom SOP), and keeping your hairgen fully procedural, you will learn to love the control and flexibility that grooming in Houdini can give you!

I'll give you one more tip to save you further frustration. Houdini needs the guides to be fairly high density compared to other DCCs, especially in areas where the surface of the skin changes a lot (think wrinkles, ears, etc.). Luckily Houdini is also much better at handling many guides when it comes to simulation and overall performance compared to other DCCs. It takes a while to figure out the right density, but I would say let the only thing holding you back from creating more guides be how easy they are for you to handle from a brushing point of view. For short fur I would go for more guides than for long fur or hair because it hugs the surface of the skin so closely.

Just in case you aren't aware of it, there are some great resources for learning grooming in Houdini here https://www.sidefx.com/learn/hair-fur/ [www.sidefx.com]

I appreciate the responses from you two on this topic. It definitely is frustrating to deal with, the SOP being destructive, though it’s nice to see there are alternative approaches.

Thank you very much! Going to try these out.