instance facing (rotation)

[vfortin]

Hi mickna,

In a recent version of Maya, they implemented some new features for goals from which you can get the target normal. I guess that would be a good start.

For the math, I'm not very good at that but I think you could take your particle's rotation X for example and linstep toward the normal X. Doing that for each rotation component as the particle approach the goal should orient it in the right direction.

I'm sure there's a better way for doing that, maybe with a matrix-interpolation-thign.

Anyone?

[mickna]

Hi vfortin!

Thx for your Replay.....
Jep, I have Maya 8.5 and see a lot of rotation Options for the ParticleShape. However I tried a few and don't get any result.

"maybe with a matrix-interpolation-thign"
Wahhhh! That's my problem ;)
I just wanna yell "I'm creative!" to hide my ignorance with Mel, Math and matrix-interpolation-derivative-double integral-things *lol*

[vfortin]

Haha well my technique obviously involves some scripting... unfortunately.
But it should be doable... I'll give it a shot as soon as I have time.
I'll probably stand corrected by then by some bilinear-matrix-logarithmic-lovers out there ;)

[vfortin]

Ok just to follow up a bit on this...
GoalWorldNormal0PP works very well. If you pipe it directly in the rotation input (particleShape>Instancer>Rotation Options), your instances will follow the surface normal properly.

I'll figure out the rest later, it's friday already ;)

Vincent

[vfortin]

Well for the records, it seems that the procedure for interpolating rotations isn't that trivial.
The trick is to convert rotations to a unit quaternion and then do a slerp (spherical linear interpolation) on it. However I can't find these commands in the MEL reference, only in the API.

[Starrider]

thats it ...

MVector vResult;
MVector vn0, vn1;
MVector v2;

double dL0 = v0.length();
double dL1 = vTarget.length();

vn0 = v0.normal();
vn1 = vTarget.normal();

double dot = vn0*vn1;
double theta_0 = acos(dot);
double theta = theta_0 * dWeight;

v2 = vn1 - vn0 * dot;
v2 = v2.normal();

vResult = vn0 * cos(theta) + v2 * sin(theta);
vResult *= ((dL0*dWeight) + (dL1*dWeight))

return vResult;

it's api code but i think it should also be possible in mel!
have fun!

[mickna]

@vfortin:
Thx for your time!
After three days thinking, try & error (error was the only success) I did it now quick & dirty. Now I have only to build up a room (cube). So I took every side and definied it as a goal. Means six emiters, six planes, emiter01 -> goal plane01 and so on.....
This works for me now. However, I'd like to know the answer.....


@Starrider:
Thank U!
Api? I've heard about it *smile*
Mel is a challenge for me.
API is a miracle for me....
Anyway - thx also for your time!
May one day, I know what this lines means.....

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