instanced particle banking + velocity orient?

[MrFace]

here's what i've done to try and do this. it doesn't work, since velocity information doesn't directly translate to a rotation vector.

vector $velocityVar = particleShape1.velocity;
float $xrot = sin(time*2+particleShape1.particleId)*10;
particleShape1.randRotation = <<$xrot,$velocityVar.y,$velocityVar.z>>;

i've set rotation to randRotation in the instancer rotation options. this code makes the particle instances wobble like i want them to on their x, but velocity values are too small to make them change appreciably on their y and z, let alone orient them properly along their velocity vector.

[MrFace]

this looks like the solution: http://forums.cgsociety.org/archive/index.php/t-199245.html

but i don't really know how to do it :cry: . any suggestions?

[MrFace]

i've gotten ths far:

if (!!particleShape1.velocity) {
prevVelocity=<<.001,.001,.001>>;
};
vector $velocityVar = particleShape1.velocity;
vector $prevVelocityVar=particleShape1.prevVelocity;
float $xrotRand = sin(time*2+particleShape1.particleId)*20;
float $r=sqrt(pow($velocityVar.x,2)+pow($velocityVar.y,2)+pow($velocityVar.z,2));
float $z_theta = atan($velocityVar.y/$velocityVar.x);
float $y_phi = acos($velocityVar.z/$r);
float $prev_r=sqrt(pow($prevVelocityVar.x,2)+pow($prevVelocityVar.y,2)+pow($prevVelocityVar.z,2));
float $prev_z_theta = atan($prevVelocityVar.y/$prevVelocityVar.x);
float $prev_y_phi = acos($prevVelocityVar.z/$prev_r);
particleShape1.randRotation = <<$xrotRand,rad_to_deg($y_phi-$prev_y_phi),rad_to_deg($z_theta-$prev_z_theta)>>;
particleShape1.prevVelocity=particleShape1.velocity;

my little shapes seem to rotatin the right direction on the z, but not on the y. i dunno. very confused at this point.

ok i made things more complicated than i needed to. here's where i am. the particle instance does orient itself toward it's velocity vector:

vector $velocityVar = particleShape1.velocity;
float $xrotRand = sin(time*2+particleShape1.particleId)*20;
float $r=sqrt(pow($velocityVar.x,2)+pow($velocityVar.y,2)+pow($velocityVar.z,2));
float $z_theta = atan($velocityVar.y/$velocityVar.x);
float $y_phi = acos($velocityVar.z/$r);
particleShape1.randRotation = <<0,rad_to_deg($y_phi),rad_to_deg($z_theta)>>;

now if i can just make the thing wobble predictably using the $xrotRand, i'll be done!

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