issue with piston animation with chop and constraints

[FR3D]

I am trying to animate an engine using chops and constraints.

I manage to get something quiet close but it isn't accurate(cheat)

My main issue is that i cannot find how to use a "look at" in conjunction with some restriction to force the tip of the arm to slide along the Y axis.

I tried many other solution as well as trigonometry(which i am not very good at) which i gave up on.

i also tried with bones but again my knowledge is close to none in houdini and i wasn't able to restrict bones

 

I wish to achieve the real thing with your help

 

Thank you

piston.hip

Edited March 14, 2017 by FR3D

[FR3D]

Ok, i managed to get the trigonometry formula.

Now i have two method.

one is Hscript which works perfectly(u can check the measure sop) and the other one is VEX.

For some reason the Vex(into a point wrangle)works but is speed up.I am pretty sure it is the same script.

Does the wrangle node manage "@frame" differently than "$FF" in hscript?

piston trigonometry.hip

Edited March 14, 2017 by FR3D

[3dome]

nope no difference between $FF and @Frame (when bound to float attrib).

the reason your file isnt working correctly is because in VEX for cos/sin you have to provide the value in Radians. Apparently hscript is fine with Degrees.

here you go: @P.y =  @r*cos(radians(@a))+sqrt(pow(@l,2)-pow(@r*sin(radians(@a)),2)); 

[FR3D]

11 hours ago, 3dome said:

@P.y =  @r*cos(radians(@a))+sqrt(pow(@l,2)-pow(@r*sin(radians(@a)),2));

Thank you 3dome.

I will clean my file, and share it in the days coming.