nkint

Hi!
I'm going to code some 3d creatures like snakes or tentacles.
For inspiration i've looked for some code around on the net and i've found this one:
http://www.openproce...org/sketch/8405
ok, i like it.

It is a simple structure: a list of nodes, the first node is the main direction, the other nodes follow the first in a fluid and

wiggly way.

the algorithm is quite easy:

1 calculate the position of the head (the direction of the creature)
2 this procedure is used:




[source lang="java"]void move(float headX, float headY, float headZ) { float dx, dy, dz, d; // node 0: position, direction, orbiting handle nodes[0].x = headX; nodes[0].y = headY; nodes[0].z = headZ; // node 1: muscule count += muscleFreq; nodes[1].x = nodes[0].x ; nodes[1].y = nodes[0].y + PApplet.sin(count) ; nodes[1].z = nodes[0].z + PApplet.cos(count) ; // apply kinetic forces down through body nodes for (int i = 2; i < nodes.length; i++) { dx = nodes[i].x - nodes[i - 2].x; dy = nodes[i].y - nodes[i - 2].y; dz = nodes[i].z - nodes[i - 2].z; d = PApplet.sqrt(dx*dx + dy*dy + dx*dx) *ks; float dx_d = + (dx * girth) / d; float dy_d = + (dy * girth) / d; float dz_d = + (dz * girth) / d; nodes[i].x = nodes[i - 1].x +dx_d; nodes[i].y = nodes[i - 1].y +dy_d; nodes[i].z = nodes[i - 1].z +dz_d; } }[/source]

with girth as a random number near between 5 and 15  and muscleFreq between 0.1 and 0.2 i get nice results.

now, i understand that this is not the real inverse kinematics but.. if i check on google about IK i found a lot of maths and a lot of methods like angles, CCD, Jacobs..
my question is:
i just need to make wiggly creatures. what is this algorithm?
or even.. can you advice me some articles or other way to make chain snake-like creatures?

hi, i haved resumed some old code.

my problem is in parallel transport approach. i've coded it in java and for some curves it works perfectly, for example trigonometry parametrized curves suach as circle, spirlas, elicodes, toroide, etc..

here is an example:

[source lang="java"]// PQ Knot toroideLineStrip3D vertices = new LineStrip3D();int p = 2;int q = 4;float theta = 0.1f;float dt = ((MathUtils.TWO_PI) / curve_length);for (int i=0; i < = curve_length+1; i++) { float r = MathUtils.cos(q*theta) + 2; float x = r * MathUtils.cos(p * theta) * 50; float y = r * MathUtils.sin(p * theta) * 50; float z = -MathUtils.sin(q*theta) * 50; theta += dt; vertices.add(new Vec3D(x,y,z));}ptf = new ParallelTransportFrame(vertices.getVertices());tube = new Tube(ptf, 6, 10);tube.computeVertexNormals();[/source]


it works nice:



now, i'm trying to do a tube on mouse drawing, and i'm getting weird results:




:
the tube framing is somewhere stopping and i can't understand why.
somewhere the normals and binormals are always equals to Vec3D(0,0,0).

here is a pics of only tangents (red), normals and binormals (green and blue)



i also noticed that the problem persists also if i try to use a straight line as a curve..
(the tube is not drawn at all)

can someone can give me some ideas?

parallel transport approach code is here:
https://github.com/n...sportFrame.java