i m trying to move particles in a conical spiral path from top to
bottom which some thing looks like a tornado… in c++
so kindly help me in with a solution
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You have two problems. One, how to calculate a spiral path along a cone,
and two, learning steering/flocking algorithms. The first is to simply
write a function f(x,y,z) that behaves like an Archimedes spiral or some
such. See Wikipedia for the math behind different spirals. Then, the
right algorithm would allow you to move particles along the path. See
http://www.red3d.com/cwr/boids/ as an
example for the flocking of birds.
Of course, one should mention that tornadoes do not follow a single 3D
Here I am writing a lengthy reply about how to construct great looking
tornadoes, but then looking at the OP question I realize Reed pretty
much answered it…
/me back to work.
Are you making rpg spell effects or what? ;)
no rouncer its a tornado effect
I was doing some more WebGL work and thought it would be interesting to
do a tornado effect, so I came up with this.
I believe the effect here closely mimics how things were done in
Sacrifice and Giants: Citizen Kabuto. I’m using a Bezier curve to
construct and animate the funnel. I didn’t have any decent textures on
hand to emit a particle cloud around the funnel (which would give it a
nice puffy look), so you could say it’s a naked twister ;)
I used 4 control points, which allows the tornado to bend in interesting
ways. The screenshot below is an example I created in Blender. This
curve has only 3 control points.
You can use the middle and ground points to control the twist and curve
of the tornado, simulating ground wind.
You calculate the mesh by using a tubing algorithm (which primarily uses
Reed’s circular formula). The tubing algorithm is exactly how you would
construct a cylinder. You construct multiple circles at each level in
the curve. You can add as many levels as you want for more resolution,
and each circle can have any number of points. Using the direction
vector of the curve, you construct a circle around that point and then
connect its edges with the next circle you will create in the curve.
Each control point contains a radius, which defines the size of the tube
at that point. You linearly interpolate that radius as you move along
the curve. So in the example above, the ground point has a radius of 2,
the middle has a radius of 5, and the top has a radius of 10.
The wireframe should look something like this.
Now all you have to do is write logic to move the tornado around. Due to
the nature of Bezier curves and how the 3D meshes are constructed, you
can also animate the birth of a tornado. You can display the top portion
of the funnel and slowly build on it until it connects with the ground.
On another note, this same algorithm can be used to generate trees.