Mastering Hair Physics: Tips & Tricks for Smoothly Simulating Hair Movement

[papillon68]

Hi, I'd like to ask some help and suggestions about simulating hair physics (so basically pulling hair vertices around, and smoothly disposing the adjacent ones).

Please take a look at the embedded video (which shows an application tha can do it): the hair displayed there is made of 15 vertices; once the user drags the active vertices (those inside the circular cursor area), all the hair vertices are moved and repositioned accordingly. To notice that hair length remain the same during the process.

Thanks for any help.



https://www.youtube.com/watch?v=lW4sa_vXBRg

 

[papillon68]

Sorry, I had troubles embedding the YT movie, now it's there.

 

[Nanako]

suggestions. you're going to need to model whatever it is that makes the hair stand up on end again, after being pushed down. elasticity? stiffness? i don't know what it's called. but generally, your video shows hair behaving like a string of dough, which doesn't seem authentic. usually if you push the middle of a hair to the side, the top will bend with it, and the whole thing will just bend at the point of contact. of course that depends on how long it is.

 

[256bits]

It basically looks like a Bezier manipulation of a line to adjust the curves. Try out any program that has Bezier curve shaping, and you will see the same effect, although the length of the line or hair would not stay the same in most programs.

Whether or not a hair will behave like that, is beyond my knowledge of the physics of hair. But if a hair is being manipulated in a viscous fluid or gel, one would think something similar would occur, depending on the viscosity of course.

 

[pmacias]

I am happy to provide some suggestions for simulating hair physics. First, it is important to understand the basic principles of hair movement. Hair is made up of protein fibers called keratin, which have a natural elasticity and can stretch and contract. This elasticity allows hair to move and bend in response to external forces, such as wind or gravity.

To simulate this movement, it is important to use a physics-based approach. This means using mathematical equations to model the forces acting on the hair and how it responds to those forces. One common method is to use a mass-spring system, where each hair strand is treated as a series of connected mass points (vertices) with springs in between. When a force is applied to one vertex, it will affect the neighboring vertices through the springs, resulting in a smooth movement.

Another important factor to consider is the collision between hair strands and other objects. In the video, the hair moves smoothly without intersecting with the head or other hair strands. This can be achieved by implementing collision detection algorithms and adjusting the hair movement accordingly.

Additionally, to maintain the length of the hair as it is being pulled or moved, you can use constraints or forces that act to keep the hair from stretching or shrinking. This will ensure that the hair maintains its natural length and does not appear distorted.

In terms of the application shown in the video, it is important to have a user-friendly interface that allows for easy manipulation of the hair. This can include features such as adjusting the strength of the forces applied to the hair or changing the number of vertices to create different hair densities.

In conclusion, simulating hair physics requires a thorough understanding of the fundamental principles of hair movement and the use of physics-based methods. With careful implementation of these techniques, you can achieve realistic and smooth hair movement in simulations.