Animation troubles with chain

[sakura13]

Hi guys,

I'm really desperate I'm trying for several days to animate a chain which pulls an object backwards and rolls in, I tried with Bones and ik spline but collides, I tried with Path deform works partially but then goes through the object when tilting I'm really desperate and don't know what to do. It is clear that it goes through because the chain swings completely instead of staying in place and only a certain area moves but I have no idea how to solve this.

Here is the animation

and here is the construction where the chain should go

Hope who can help me greetings

[sakura13]

Ahh now Iam understanding why you was confused about editable Poly, 1 object was for me one item I did now a seperated Version for you.

[leeminardi]

@sakura13 I think I have a good approach for rigging the chain motion.  Please see the attached file.

My strategy was to control the the shape of a spline via the position of 6 points.  Position Scripts are used to position these points.  The mechanism is considered to have 3 rollers (A,B, and C) which the chain must pass over.  The 6 points indicated in the image below.

Point 1 - is part of the Scoop object and is linked to it.

Point 2 - a point on the A roller that is at the point of tangency of a line tangent to roller A and roller B.

Point 3 - midpoint between points 2 and 3.  This point is helpful for ensuring a straight spline segment between point 2 and 4 but does cause some problems when the scoop rolls far back.

Point 4 - tangent of line reference by point 2.  Technically there should be 2 tangent point for roller b. This on and one for the line tangent to rollers B and C.  The difference is so small that I ignored this detail.

Point 5 - a point to control the shape of the spline as it passes over roller C.   Again, 2 tangent points could be used here but one provides satisfactory results if the spline's vertex is "smoothed". 

Point 6 - a point to control the path of the spline after passing over roller C. Technically the chain should wrap around roller C but this is very difficult to model and may not be visible in a final animation.  I decided to just have the chain disappear  into the floor of the cart and hope no one would notice!

The position and rotation of the scoop is controlled by the position of Dummy001 via a Wire Parameter.

The geometry of the cart and scoop do not seem to be correct as the scoop is beyond the cart body when the bottom of the scoop is parallel to the ground.   There also seems to be some interference between the scoop and the internal mechanism (blue).  The model should be corrected and then the rigging adjusted.

The calculation of the tangent points 2 and 4 was a bit challenging. I prefer to work in World coordinates so local positions are converted to world then the intersection point of a line passing through the center of rollers A and B with a line tangent to the two circles is determined.  From there, with a little algebra and vector math, the tangent point is determined.

Here's a Screencast of the animated results.

https://knowledge.autodesk.com/community/screencast/7f8f9e9e-969e-4f38-b902-9a8e023b1c21

[leeminardi]

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@sakura13 wrote:

... how can i learn this anyway how do i start with animations like this do you know any good tutorials so i can learn this as well? ...

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@sakura13 I think the best way to learn creating Max scripts is to start with something simple and work up from there.  I have created a few tutorials but there are many more in youtube.  Start with 2D problems and work you way up to 3D.  Keep and eye on the Max 3ds Max Rigging and Animation forum for solutions to a variety of problems.

Here are a few of my tutorials you might find helpful.

1.  3ds Max Tutorial - Part 1 - Slider-crank mechanism with Expression Controllers  an introduction to Expression Controllers.
2. 3ds Max Tutorial - Slider-crank mechanism Part 2    - an improved version from Part 1.
3. Rigging a Telescoping Beam - another simple 2D Expression Controller example.
4. Using Matrices to Rig a Scissor Mechanism in 3ds Max - an introduction to Matrices and Transform script in a 2D application. 
5.  3ds Max Tutorial - Rigging a Hexapod - more details about transform scripts and working with matrices but in 3D. 

I realize that some Max users may not be familiar with vector math.  I don't know your math background but if you have any questions don't hesitate to ask.  I find working with vectors more intuitive than trig once you understand a few basic concepts.  If you are a 3D thinker it is easier to grasp. We are all learning!

Regards,

Lee