Geobased Hair

[Rodney]

One of the things I like about A:M is how we can develop our own approaches to things and extend the tools that we already have.

 

Considering recent discussion on hair I thought I'd explore some of the area I hadn't pressed into yet with hair based on splines shapes. One of the primary reasons to use particles for hair is to gain some dynamic capability and to prevent intesections and pass throughs of the hair. With geometry based hair one approach to would be to use Simcloth to prevent the inter-penetration of each hair.

 

Attached are a few of my tests as proof of concepts:

 

Further refining the geometry and adding patch images or decals of hair to the actual geometry is what would recreate the various looks, textures and dynamics of real hair.

 

I am not exploring the use of flat patches for hair because that is already well documented elsewhere. What isn't well documented in that area is the use of cloth with flat patches with decaled images of hair.

 

If should be noted that perhaps the best way to initially groom geobased hair is to use Magnet and Mirror modes and Distortion Cages work fine as well.

 

Edit: I've added a project file but I have absolutely no idea what is in there...

PoC_GeobasedHair0.mov

GeobasedHair.prj

[Rodney]

This started as a test to see how well splines by themselves would work as hair.

At the last minute I extruded in order to increase the density.

 

What was interesting about this foray into spline based hair was the thought that if developed it could yield an interesting way to cut hair. It's very easy easy to cut the hair (see cut out smiley face in the attached patch of hair) but I'm not sure how to grow that hair back again. I think that would either take a programmatic approach or require patches to get there. Hmmm... I suppose scaling would be the primary tool for faking cut or growing hair. I'll have to look into that as well.

[Rodney]

Here's one that is all splines using Render as Lines. This approach would likely work best for kinky hair as that is harder to achieve in patch based hair.

splinebasedhair_sm.mov

[Wildsided]

Very interesting concept Rodney. Does this use more or less processing power than particle hair. If there's on thing I hate about particle hair is that it bogs down my computer when it's turned on.

[Fuchur]

Very interesting concept Rodney. Does this use more or less processing power than particle hair. If there's on thing I hate about particle hair is that it bogs down my computer when it's turned on.

 

You may want to decrease the realtime-option at the hair-material.

 

See you

*Fuchur*

[robcat2075]

If there's on thing I hate about particle hair is that it bogs down my computer when it's turned on.

 

You may want to decrease the realtime-option at the hair-material.

 

Find the Density Factor property under Hair System>Realtime

 

 

It can be set very low and still give you a sense of hair position and movement

[Kamikaze]

Rodney

 

I love this type of experimentation ...... and the idea of patch based? hair

Will keep checking in to see what you come up with.......

[Rodney]

Thanks Mike, A:M makes it fun to experiment.

 

Here is a test I did today with Render As Lines.

All of the splines here are straight lines exactly identical except the last one on the right (which is two lines that form a patch)

It's interesting to see what shows up just with adding a new level of detail via a new Named Group.

[Kamikaze]

Rodney,

 

Nice ref. I know Ive use RAL on the C130 model for the antenna cables.....It seems there could be more options for RAL .... but right now can't think of anything after a night work..

 

Mike

[Rodney]

It seems there could be more options for RAL

 

I'm sure there is. Some of those we can probably do right now... we just don't know how to do that already.

 

Yesterday I also tried a cracked glass look but I didn't think it was worth posting.

 

Patches will always be more powerful for getting splines into 3D space but RAL does have some nice uses.

I think RAL would need a major rewrite to take advantage of anything much more significant and that'd be a particularly expensive endeavor given that few use it.

 

I read a tech paper not long ago that suggests a way we could fake some of the more powerful RAL stuff by creating the framework ourselves and because with A:M we can often create our own solutions I may just give that a try.

 

There is one aspect of the current RAL that keeps it from being of practical usage in my work and that is the ability to taper the ends of the line. But for this it's fairly easy to just change to patch geometry (see above example all the way to the right).

 

The one tool that I've found to be of most use with RAL is Snap Group to Surface because with that we can get any and all of our splines to conform to an object's surface. The secret to Snap Group to Surface is Named Groups. Just name a group of splines, position it in front of the object you want to have the splines conform, right click and SGSNG! Once in place the easiest way to get tapered lines is to use Sweeper to add tapered geometry to those lines.

 

Added: This isn't hair but follows the same principle of Geobased Hair. What I think is particularly interesting about it is how that we can decal objects with geometry rather than graphics.

 

Note: I don't think we can Snap Group to Surface in a Chor. If we can then we can do those fancy things where objects can appear all over the surface of an object in a few short steps.

[Simon Edmondson]

Rodney

Pardon me but, I've never used cloth or the render to lines option. Could you give a brief outline of the method you used as I'm still having trouble with particle hair and would like to try and finish the project .

regards

simon

 

Ps

I'm finding that, once groomed and saved, when I open the model file the next day the style has altered

[Rodney]

I'm finding that, once groomed and saved, when I open the model file the next day the style has altered

 

Are you baking your particles?

 

 

 

As far as my approach to geometry based hair there are quite a few tutorials on cloth so it might be best to point you to those.

In the meantime I'll offer this:

 

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Cloth Simulation

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The basic approach is:

 

Create two materials:

1 - Cloth

2 - Cloth Deflector

3 - Apply those to meshes and then simulate

 

Rename these materials as Cloth and ClothDeflector or something easier to find later. (A:M doesn't automatically name them anything particularly useful so we have to do that)

 

Create the mesh that you will use as hair, fire, smoke or whatever you will be attempting to create via the cloth simulation.

 

Considerations: When dealing with cloth simulation there are several 'tricks' to getting it to perform with maximum control. Here are a few:

 

- Use Named Groups! By naming Groups we can not only better understand and organize we can layer in effects. For instance, having a group of objects that will serve to deflect the cloth (i.e. it has the Deflector Material applied to it) that is invisible (turn its surface property to Transparent=100%). In this way you can channel and direct the simulation in interesting ways.

 

- Consider leaving dangling splines outside of the area to be simulated. These will ground the cloth to something stable that will not be directly effected by the simulation. In the case of hair these might be below the surface of the 'skin' that the hair will appear from. I try to select these dangling splines and name them something like 'base' so that they can be modified later.

 

- Consider the distance from each object you've created. Overlapping meshes will cause the cloth simulation to error out because it can't properly calculate the interactions and directions. (i.e. it doesn't know which way is up because we've confused it by having interpenetrating meshes)

 

- Consider saving out/exporting a frame of the animated simulation as a separate model. In this way you could generate thousands of resources simply by launching one simulation. We then can animate those separately or... simulate them again in other ways.

 

 

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Forces

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Adding forces (via Right Click/Add/Force) in an Action or Choreography allows us to push and pull geometry around in a dynamic way.

This is especially useful for cloth simulation. We can hide or lock objects or add invisible objects in between the force and their location to 'protect' them from being effected in the same way as those areas that are fully effected.

 

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Render As Lines (RAL)

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Render As Lines is considerably more basic than cloth simulation and is not as versatile because there are no patches. It is important to note however that RAL can and generally should be augmented by the use of patches. For example you might have a cool looking robot and just add some detailed lines over the top of the robot's mesh to add the appearance of additional details. With v17s new 'Snap to Surface' features adding splines to the surface of a model is easy whereas before we had to painstakingly turn our models around or view them from multiple angles simultaneously to make sure the lines were on the surface.

 

In my estimation the secret to RAL is using Named Groups to layer in of additional properties on the same splines/shapes. Using a little roughness and then adjusting the scale of that roughness can create some very interesting effects.

 

Because RAL does generate some rendering artifacts on occasion it's often best to take this one step further and convert the splines to geometrical (patch rendering) shapes. This is trivial and easy to do with use of the Sweeper plugin. Just draw a little spline shape (say three CPs connected) and name it as a Named Group (because I will delete it later I often name mine, "Use Me". Then I can easily find it in the Sweeper dialogue.

 

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Sweeper plugin

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The Basic Steps to use Sweeper:

 

Create the splines you wish to sweep (It's best to Name this as a Group although technically it isn't necessary)

Create the shape or object you wish to sweep (name this Group)

Select the splines you wish to sweep

Right Click and go to Plugins/Sweeper

Select the shape you wish to sweep from the list of Named Groups in the drop down menu

Adjust other parameters as necessary

Launch the sweep

 

The swept shape will automatically be named so it will be easy to move away from the splines used to create it. That original spline can then be adjusted or used for additional sweeping or discarded. If the swept object isn't to your liking simply delete it and sweep again with different settings. Move them to the side if you wish to compare multiple sweeps with different settings.

 

 

That is a basic primer for the areas under consideration.

 

As I mentioned before, I haven't actually pressed into the classic use of decalled hair that is then cloth simulated. This is especially powerful because we can use Patch Images (with all of their various Image Types) to layer in the hair. That hair can then be further animated/simulated.

 

It should also be noted that once we've got the geobased system in place we can further augment that with particles based effects (to include but not necessarily requiring particle hair). For instance, geobased hair might be further enhanced through the use of sprites or blobby effects. The general premise being to accomplish what we can with simple geometry and use particles to achieve what cannot be easily achieved complex geometry and interactions which is what particles attempt to simulate.

[Simon Edmondson]

I'm finding that, once groomed and saved, when I open the model file the next day the style has altered

 

Are you baking your particles?

 

Rodney

 

WOW !!!

Thats a comprehensive outline. Thank you very much.

Tomorrow will be very busy.

 

re Baking particles. I didn't know that was necessary. How is it done ?

regards

simon

[NancyGormezano]

I'm finding that, once groomed and saved, when I open the model file the next day the style has altered

...

 

re Baking particles. I didn't know that was necessary. How is it done ?

 

First, I'm not familiar with how well or not hair works in vers 15j+ on Mac.

 

You do not NEED to bake hair(particles). I suspect something else is going on. Baking of particles/hair has NOTHING to do with how grooming might get altered in a model file. It only has an impact on how it behaves in a choreography, and usually one only bakes hair/particles if the hair has dynamics turned ON. Baking is an option in the chor, and the baked hair files will be created and saved to the same folder that the project has been saved to. The "baked" files (extensions with pai, and par) - contains the data as to how the hair will move, so that one can tweak the animation with the actual dynamics of hair pre-computed, and that one hopefully will get consistent results if one is Net rendering (using multiple computers).

 

Try a test case with a simple sphere model, add hair to some of patches, groom it, save the hair material as an external file (don't embed it), save model as external file (don't embed). Then reopen A:M and bring in model with hair. If something has changed with the grooming then there is a bug in 15j+ with macs.

 

I have found that sometimes I need to create a hair material, add the hair to the model, save material, save model, close A:M, then bring it back. THEN groom the hair (and resave model) - As sometimes the first grooming doesn't take (or something like that), but from then on it does. So it may be you are running into something similar

[Simon Edmondson]

...

I have found that sometimes I need to create a hair material, add the hair to the model, save material, save model, close A:M, then bring it back. THEN groom the hair (and resave model) - As sometimes the first grooming doesn't take (or something like that), but from then on it does. So it may be you are running into something similar

 

Nancy

Thank you very much once again.

Dynamics is turned on with a pre roll of 20. I groomed it on the Mac the, because it wouldn't render properly on that, it is going through on an old PC that was about to be recycled somewhere. I will try your suggestion straight away.

regards

simon

[Rodney]

re Baking particles. I didn't know that was necessary. How is it done ?

 

As Nancy has indicated baking is not necessary.

I don't think we can bake particles in a Model. (that is an interesting thought however...hmmm)

I was assuming you were still having issues with controlling particle hair in your animation and grooming is just one aspect of that. I think we can groom hair just about anywhere (Model, Action or Choreography).

 

If I understand baking of particles it is primarily a means to get simulation settings to lock down so that A:M doesn't continually have to update, calculate and recalculate those settings. It will also be useful when using Netrender because Netrender would otherwise recalculate everything all over again which can lead to unintended variations in those calculations. Baking (basically) keyframes the results of the particle simulation.

[NancyGormezano]

Dynamics is turned on with a pre roll of 20. I groomed it on the Mac the, because it wouldn't render properly on that, it is going through on an old PC that was about to be recycled somewhere. I will try your suggestion straight away.

 

Didn't quite understand what you were saying with respect to using a Mac or PC?

 

However...

 

Why pre-roll of 20 frames? That will complicate your life, & make working with hair more difficult, time consuming (computationally a pain). I know others do the pre-roll thing, but I have no idea why, other than I suspect they are wanting the hair to settle due to gravity (makes like a wet noodle), but I choose to groom the hair in the model and set the USE gravity = OFF, but USE forces = ON. That way the resting look of the hair is exactly how I groomed it, not how A:M computes it to look after "coming out of the shower". The hair will still be dynamic according to how the head moves. I also like to up my drag to 20% (to make the hair less floppy responsive, and make the dynamic stiffness = 30%) - You can tweak to taste. Also - important if you don't want flickery stuff going on, then "set face camera = 0%". If you have it on, it will also impact your grooming look.

 

I like to keep things as simple as possible (not necessarily as realistic as others prefer)

Edited November 3, 2012 by NancyGormezano

[John Bigboote]

Interesting thread... I've tried making strands of hair and applying cloth to it... I forget where those tests are. I do use the 'pre-roll' option... sometimes as much as 4 seconds of pre-roll- it takes an extra 10-15 seconds before the render, so not that big a deal. I use because- as Nancy stated... I choose to use the hair's gravity option. For my 'avatar-babe' I have the long hair in back using gravity and is UNgroomed, so because it's long and has very little drag- needs about 2 seconds of pre-roll... whereas the GROOMED hair on the top of her head is shorter and does NOT use gravity- so no pre-roll on that. You can see a bigger example in the link below my signature, AVATAR.mov.

[Simon Edmondson]

...

 

Didn't quite understand what you were saying with respect to using a Mac or PC?

 

...

 

I don't want to take over Rodney's thread so I will post the result to the Hair Ball thread.

 

Just before I do.

 

I was having trouble with hair on the Mac and did a test. It would not behave under OSX. So I tried the same project on an old PC under XP. It worked. I then tried the model groomed on the Mac on the PC, which is where I lost the grooming.

regards

simon