information about vortex modifier

hi there,
i m ganesh from bournemouth UK, doing my Msc Computer Animation and Visual Effects..i went thru the vortex modifier......i couldnt understand the tPosition and tDirection .....vectors.

and where will we intialize the transform position and tranform direction .....

i really cant understand the principle behind those parameters



kindly help me out

cheers,
ganesh

Hi, tPosition and tDirection vectors are the transformed position and direction vectors of the vortex. They are computed from the position and direction of the vortex and from its transform.

By default as the transform is a unit matrix, tDirection and tPosition are equivalent to direction and position. To set a transform for a Transformable object, just take a look at the transformable class. Once a local transformed has been set, it needs to be updated with a call to Transformable::updateTransform. Generally you do that at the root level ie the system that contains the vortex modifier.

thank u..juff...

and can u jus tell me the principle of this vortex..is there any reference material.......over the net

so that i can reproduce the same stufff...(jus for the sake of learning).....

don mistake me

cheers,
ganesh l

The reference on the net are in the source files of the vortex. The vortex documentation says :

Quote :

A modifier defining a vortex in the universe.

A vortex is a spinning flow around a center. Its center (its eye) is defined as a line in the universe.
In addition to its center line, a vortex is defined by 2 speeds :
the rotation speed which defines the speed of rotation around the vortex eye.
the attraction speed which defined the speeds at which a particle is attracted by the eye (or repeled).

The rotation speed can be defined either in units per second or in radians per seconds. In the first case, the closer to the eye particles are, the faster they will spin around. In the second case, the speed is constant.

The attraction speed can be either constant or linear (function of the distance to the eye). In the second case, the farther particles are from the eye, the faster the are attracted (or repeled). First case can be assimilated to a Archimedes' spiral while second is more a logarithmic spiral (Bernoulli's).
The vertex eye radius can be defined. The user has also the possibility to tell the vortex to destroy particles that enter its eye automatically.

Note that this modifier does not update particle's velocity. Therefore particles modified by a vortex does not have any inertia.
This is because defining an accurate vortex in a discrete environment cannot be performed by using the derivatives of the position and velocity.

For the implementation / algo / math, just take a look at the code. Also, the galaxy demo illustrates the Vortex modifier in action
What do you want to know exactly ?

well, i want to do a tornado simulation in c++ opengl...

for that i jus have an idea of having a funnel particle system,and a debri particle system.....

a plane emitter class,and a force class which contains vortex,turbulence...........


if u have any idea of creating a tornado simulation jus give me an idea....

esply i have problem in creating a emitter(square emitter or cube emitter)..and pass that emitter to my particle sytems...

both debri and funnel system.....



kindly guide me..

So if I understand well, you re developping a particle system from scratch without using SPARK ? In that case I cant really help you. You can find some inspiration in the source code of SPARK if you want.

Another thing you can do is using SPARK for the update and rendering of your particles and implementing a custom modifier that will give your particles the correct tornado behavior. So that you can tune the behavior exactly the way you want.