So here’s what I want to accomplish. I have two physics objects and I want one to be a weight for the other. Take a fishing lure for example. The one object floats but the other object is a weight that does not float. I want to weight to drag one end of the lure “down” as the lure falls through the water.
How would one go about attaching a physics object that acts as a weight?
I’ve tried attaching a weight with a much higher mass and setting “Is Kinematic” to true but the behavior is not what I expect. I also tried making it a fixed joint and attaching it but then the whole thing floated off into space.
Please help me to understand what I am doing wrong here.
Doesn’t that just push it one way though instead of rotating it?
Here is what I want to have: a small weight attached to a larger spherical object. In this example the weight would rotate the spherical object as it fell through the air. In my tests the spherical object doesnt rotate no matter how heavy the weight is I attach to it.
Think about attaching a 50lb weight to a soccer ball for example and dropping it off a tall building with the weight on top of the ball. Before it hit the ground you would expect the ball to rotate around to where the weight is on the bottom, right?
Well, you have to give each a rigid body and a relative weight, with a joint of some sort. But if you give each one identical drag, it will not rotate. In what I was finding, whichever one had the most drag would end on top, when in a freefall, which is normal.
This seems to go back to the acceleration due to gravity being independent of weight. If you want to influence this a bit, applying drag to the items can help you a bit.
Another example would be a pole with a bowling ball attached to the end. If you threw it off of a building, horizontally, I would expect the bowling ball to rotate around and end up at the bottom before it impacted the ground.
I have the weight as a child of the parent and then a fixed joint but thats not working. Do you suggest some other configuration? I also forgot, I am using two different drags to simulate wind friction.
I also tried making the sphere it’s own object (no parent), with a fixed joint, but it just falls to the ground faster and does not “lock” itself to the pole.
You should be using a fixed joint. Then, the bowling ball would have less drag, to simulate the mass that it has to overcome the drag in real life, and a lower amount of drag on the pole. Also, you have to make sure you are giving sufficient time for the formula to work itself out. If you were to drop a pole with a bowling ball on one end from 10m, the ball would hit first, but not by a huge difference in time. If you did that from 100m and slowed down time, you would see that the pole, having both less drag and less weight, would end up above the bowling ball.
We can go over these examples all day long, but at the end of the day, in a vacuum all things fall at the same rate, regardless of mass and how we connect them. To simulate air resistance, we have to use the drag variable.
I am using drag, and immediately the ball falls to the ground while the pole is still falling. Shouldn’t the pole have more drag? Also, when I set the ball to have more drag it just float above the pole; hence, removing any gains from having a higher mass. Is there any way to make the ball not separate from the pole? The fixed joint doesn’t seem to fix it to anything.
As I understand it, whatever object you want to go on top requires the most drag.
All this being said, you mentioned you were doing this with a lure, for fishing?
I would treat the rigid body as an independent entity, and utilize a bone solution to create the fishing line, and it would not need to behave physically correct, it would simply have three points, start, mid and end, and have some sag in it.
This is how i would approach it on a post project, and I can’t think of an easy way to do it in unity, either
My lure example was just that unfortunately, a example. I’m trying to solve the problem for a game though and must use physics. I’m just trying to figure out how to do it with the tools we have been given. The fixed joint thing would work I believe if the two objects stay attached to one another. The problem is they split apart immediately even though I have the breaking threashold set to Infinity.
If they are falling apart, it is because they are not fixed properly. If you want to wrap up your test and upload it someplace, I can take a quick gander at it.
