Key Frame Fantasy
starboard
Posts: 452
Just a thought while working with Dynamic Hair. I find the controls obtuse, as if trying to control a pin with a magnet...They work sort of in an abstract way. So I was wondering why can't the hair be key frame controllable. I know that is why they call it "Dynamic Hair" - its dynamic, but an option giving some key frame control of hair over time would be in my view very useful. Even if it was only the ends you could control. There are probably numerous reasons why not .. Just wondering..
Starboardtack
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You can't keyframe the hair, but you can keyframe the forces that are making it move and react. For example, I can keyframe an invisible cylinder to ride outside of my character's head, then keyframe it in at a certain point if I want the hair to be swept back (like in my hair-tucked-behind-the-ear example). If I want someone to blow their hair up out of their face in frustration, I can't grab a particular guide hair and yank it up, but I can insert an invisible primitive that pushes it up by keyframing and then lets it settle back into place. Sort of workable workarounds for those situations, the invisible face shield that Philw provided in his tutorials gave me the rough idea, but since then I've realized there are tons of quick easy fixes for specific situations you can do just by putting invisible objects in the scene for the hair to collide against. I was thinking of an easy way to make a ponytail by putting a torus in the scene, parenting it to the back of the head, and brushing the guide hairs so they are all passing through the torus. I haven't done this yet, but can't think of a good reason why it wouldn't work.
Jon,
I have also been playing with different shapes using key frames to make the hair respond. I have tried multiply cylinders behaving as a rake, I have tried rotating the objects, such as a rotating cylinder, etc. I was even considering meatballs..though I have not used those yet - more to learn. ..anything that might influence the guide hairs in a more positive way. If the hair is straight it seems to work ok..but if you have a convoluted hair style where you have to use a lots of "shape" on the guide hairs, then having the hair drop over the shoulders, as the head tilts foreword is hard to pull off. When you back off on the shape so as to have it respond more fluidly, say to gravity, then it straightens out losing the hair style.
The controls seem to be a fudgey way to move the guide hairs.. As if you had a rubber steering wheel in a car. Thats why I was wondering why the guide hairs themselves, maybe not individually key framed. You would not be replacing the dynamic flow but editing or cleaning up the effect. For example, even some of the best demos on dynamic hair I have seen, still have some hair passing though the object. It would be nice to be able clean up these strays.
starboardtaack
Oh I don't disagree, it would be nice to have a bit more direct control of the guide hairs. I'm not sure if that's something that could be done and still have it be dynamic and react to actual scene forces, but it would be very useful if that were built in or added at some point (though I have very little faith in the current developers in daz at the moment; I expect Carrara 9 will be mostly fixes to make Genesis2 use more friendly/seamless).
Regarding the specific problem you mentioned of wanting volumized hair to fall naturally over the shoulders without having loose hair visibly passing through the character face, you can preserve the shape of the guide hairs with the Shape stiffness, but this is sort of like 'hair spray' and makes the hair tips not want to fall over the shoulders as easily. Originally I thought that for hair shader volumes they could work for the sides and back of the hair but not the front area around the face, as the loose hair 'spreading out' would be visible as passing through the face mesh since only the guide hairs are held back by the face shield, not the loose hairs.
My original approach (which is still valid) was to do the front hairs as a separate hairgroup that has some shape stiffness so that they will want to 'hold' themselves out from the face, but since they will also not move as dynamically as hair with no shape stiffness set the back sides and back hair as a hairgroup with no shape stiffness and all the volume comes from the hair shader (wave and kink, etc). That way you can get hair that will flow naturally over the shoulders with movement but won't go so far forward that it's visibly passing through the face mesh.
But there is another way, in the category of (facepalm) 'I should have thought of this before', which is simply to increase the dimensions of the faceshield, so that it's holding the guide hairs farther away from the face (or making the proxy head wider, which would accomplish similar results). Then you could use hair shaders for the volume of your hair, keep the hair totally loose and flowing at all parts, and so still have a nicely volume hairstyle that will flow over the shoulders naturally with character movement but still won't have loose stray hairs that could be visible going through the face.
Either way, most hairstyles with bangs or volume effects at the front I would still recommend setting a little shape stiffness because most hairstyles in real life have some stiffness in those areas where someone has curled or hairsprayed, but hopefully this will give a little more latitude.
Also remember you can have multiple hairs (not just hairgroups) on the same figure in the same place. So you could have one hair that's loose and recognizes the invisible face shield as a valid object to collide against, but at the same time if you needed bangs that would pass through some of the area that's blocked off by the face shield you could simply add a whole other hair to the head, and this one in the simulations tab could have it set so that it ignores the face shield and will fall down through it, with some stiffness in the shape to keep it from moving around too too much.
Sorry, didn't mean to ramble, but you've touched on an issue I've been actively experimenting with different approaches for a solution, so thought it might be of use.
Jon,
Some of the experiments I am doing at present is to make hair sections and render them out of Carrara individually. Then in After Effects , stacking them up and distorting the different hair group layers using Bezier Warp. Then of course render out the whole comp. I am still playing around with other AE filters - so there may be a better solution in the wings. This of course brings its own problems, such as lacking appropriate shadows, etc. More tweaking... But it is a work around. It would be so much easier if Carrara would allow the key framing of the hair groups.
Starboardtack.
Jon,
Just re-read your last post. Are you suggesting multiply hair groups stacked as layers in Carrara on the same proxy or duplicate proxies with the same co-ordinates. One group stiff while the other is loose...Interesting...Would it work ? No crashes ? I can't play with it at present as I have a lot of rendering going on. I would be fun to try.
Starboardtack
Yes, different hair groups on the exact same proxy. No crashes for me so far in testing, each hair does have to have it's own simulation as they are separate hairs, but can cover the exact same area, and have the same shaders, etc.
One other way I've been using this is to have one hair that's nothing but combed down flat on the scalp from front to back. Works perfectly as a haircap, and if I want an extreme closeup I don't have to worry that my haircap object might look a little like a flat brown dome object, because I'm not even using the regular haircap and instead am using actual hairs that are laying down flat on the scalp. For this I could set a high shape stiffness, but honestly I don't even need to run simulations for it to do it's job. :) Sorry, not what you were asking but an interesting aside.
When I use a hair cap, I fit it as closely to the head as possible. Sometimes some of it is inside the head mesh, then I disable the hair cap visibility. Hairs still show, but hair cap doesn't.
I should clarify terms to prevent confusion. There's the terminology of a hair cap, which is a proxy object the hair can be built on and grown out of (many of the daz store vendors do this) and which you then fit to the character's head, so the hair is 'parented' into place, the hair cap in this case is meant to be invisible so that it appears the hairs are growing right out of the head.
There's also the Daz hair cap object (which may or may not be the basis for the proxy hair object used as described above) which can be used for the express purpose of putting visibly on the characters hair, against the scalp, so that you can render more quickly with far fewer hairs but the haircap prevents the character from looking like he/she is going bald at the top :) because you can get away with using as few as 5000 hairs and still look like your character has a full head of hair if you use the haircap in tandem to make the roots of the hairs appear dark instead of having the scalp shining through. This is a nifty trick for making render times fly for animations, although if doing the same render as a high quality still image closeup I wouldn't use the haircap at all but would instead use higher haircount (normal haircount on humans is around 100k, for example and that many hairs can slow render times). On the other hand, the trick I was using is sort of the best of both worlds, forming an underlying visible 'haircap' out of actual dynamic hair, and still keeping the hair count very low, seems to work pretty well in my testing :)
Makes sense now that you describe it that way.
Hnmpf!
I always thought that those hair caps were actually meant for growing hair on. I know that AprilYSH made our Carrara hair caps for us, and they do look nice! But I thought they were included for the purposes of giving hair artists a consistent model for which to apply hair to.
That too, but Jon is right, the texture can help hide a lower hair count.
Bonus for those new to Carrara's hair: If you copy the hair cap's image map, and paste it into the color channel of the hair shader (root and tip), the hair will be that color.
Am I correct in my conclusions ( and truly hope I am wrong ):
1. Dynamic Hair is a whizz at working with straight hair both still and when animated.
2.If you use Dynamic Hair to make complicated hair styles involving curls then it is a different story. It is fine for still images but when it comes to animation problems develop. Due to the controls that are available you can either choose (A) maintaining the hair style and thus have a rigid non realistic hair movement, or (B) remove some of the shape and thus have the hair style dissolve towards a straight hair model which Carrara can handle dynamically.
The work arounds so far are not very satisfactory.
Starboardtack
Starboardtack, you're not entirely wrong but also it's not as simple or cut and dried as that. I'm working on a wildly curly and volumized hairstyle to be kind of similar to the girl in Brave, and I've got more than a few ideas how to achieve it and still have it be dynamic and flowing. First I'm trying to setup and animate a proof of concept to get Carrara hair into an animation in Octane, but I figure that won't take more than a day or two if things go well, but once I'm done next thing I'm focusing on is a curly hairstyle that isn't 'frozen' like it's been hairsprayed to death. I hope to have it by the end of the week, if things go well (maybe I just jinxed myself :) ) and if it works as I think it will, I'll put it out there for free use to anyone. Volumized hair definitely has to be approached differently then the straight hair, but I firmly believe it's a do-able proposition.
While watching one of jonstarke's excellent videos, it struck me that one could possibly prevent the curled hair from straightening out during a sim by lowering the gravity?
It the anim also involved, say, dynamic clothing, one could do the clothing sim first and exclude the hair, then lower the gravity for the hair sim.
Or you could set one or the other sims to use a directional force, and the other to use the scene's gravity.
I did a basic search this morning on Dynamic Hair - just tube stuff.. Not just Carrara..I cannot find a single video that demos dynamic hair that uses even moderate curling... They all show straight hair being tossed turned and blown in the wind.. Perhaps that is the frontier of the art right now... Hope not.
I am still plugging away trying a work around. I have tried parenting a proxy within a proxy. What I did was put a proxy head B into a proxy head A..parented. Then I tilted the head A forwards and then backwards. To keep the hair strands vertical so as to follow gravity, I turned head B so that the strands were always vertical.
Although this looks promising - it is still not putting the hair on an M4 figure.
Starboardtack
You may be able to use some of the hair shaders, such as kink or wave to see how they behave.