Hello everyone,

I've got a little problem that I'm hoping some of you will be able to help me with. I'm trying to set up a trail of dominoes that will align itself to whatever curve I draw initially. The curve is laid out so that a resample controls the spacing of the points as well as the total number. Normals were then added to the points so that the dominoes could have a direction to face in.

The dominoes consist of 4 sops…

grid_dom_# - simply builds the domino
xform_Y_dom_# - controls domino Y position
xform_pos_dom_# - aligns the domino to the respective point and normal
xform_rot_dom_# - rotates the domino around the point with a clamp function that is controled by a hidden circle that moves linearly

One thing I think I should dive deeper into is the fuction that aligns the dominoes on the normals.

in the Rotate Y channel of the xform_pos_dom_0 sop:
acos(dot(normalize(vector3(point(“../point_showme”, opdigits(“.”), “N”, 0), point(“../point_showme”, opdigits(“.”), “N”, 1), point(“../point_showme”, opdigits(“.”), “N”, 2))), (vector3(0,0,1))))

(and no I didn't write that myself all of that credit goes to a fellow student)

point_showme is just the final sop of the curve that displays the points and normals.


The problem I'm having, is that when I play the animation, the dominoes only rotate about the x-axis, which makes sense, because that's the channel I have the clamp function in on the xform_rot_dom_# sop. And that's great, as long as I'm doing a straight line out the z-axis
but, I'd like to set this up so that it will look pretty on any curve.

Here's the clamp rotation function in case it would help:

clamp(chf(“../crot/ty”, $F - opdigits(“.”) * (“../resample1/length”) * 30)), 0, 80)

crot is the circle sop that controls the domino movement.

So, any thoughts on how I could set the dominoes to rotate perpendicular to their normals would be greatly appreciated.

Thank you in advance,

Jared Hromika

i'm curious as to why you are not using the copy sop?

Sounds to me like you're complicating things a little too much – you shouldn't need to use any expressions to do this (well… maybe one; but that's if you don't want to use CHOPs)

Try this:

1. Build your curve with a curve sop followed by a resample sop (much like you're doing now). The curve can have any orientation, but start building one on the XZ plane.

2. Plunk down an Add sop with a single point at {0,0,0} and a single poly with one point {0}. Follow the add sop with a point sop and set it to “Add Normals”, and put the value {0,0,1} for the normal.

3. Put down a Sweep sop and feed the output of step #2 into its first input (“Cross Section”), and the output of step #1 to its second input (“Backbone”) – leave everything at default.

4. Build your domino (just one) sitting on the XZ plane (its height in Y, depth in Z, and width in X). offset it in Z (depth) so the edge doing the X-rotation is on the X-axis (so you pivot on the edge and not the middle).

5. Add a Copy sop, and feed the domino shape to its first input (“Primitives to Copy”) and the output of step #3 (sweep) into its second input (“Template to Copy to”). Get rid of “Transform Cumulative” (but keep “rotate to normals”). Now put the “tumble” expression in the Copy's RX channel – say something like “clamp($FF-($PT*30),0,90)” – or use CHOPs for completely “expression-free” dominoes!

… that's not to say you *can't* use expressions… but you'd end up pretty much duplicating the above, so it's not really worth it.