initial velocity for a rigid body simulation: a ball rolling on a skew plane

Question

I can do a falling torus onto a plane, but I wanna have a modification: a ball moving upwards on a skewed plane and then slowing and increasing the velocity in the opposite direction as would physics suggest. My question is: how do I give the ball an initial velocity?

so the ball needs to have physics from the beginning except it's going upwards? — moonboots, Nov 12 '20 at 17:42
@moonboots mostly yes. It should just have an initial velocity so no violation of physics occurs as it moves upwards the plane. I just do not know ho do I give it this initial velocity. I expect Blender then correctly and automatically gives it the opposite velocity (smoothly) in the opposite direction. — user3357120, Nov 12 '20 at 17:45
@moonboots What do you mean by "have physics" ? "obey physics" or "have initial velocity" instead of physics ? — user3357120, Nov 12 '20 at 17:46
at the beginning you could animate your object with the Rigid Body > Settings > Animate option that you can keyframe, but it will be animation, not physics, then disable this option, keyframe, and let the physics act on the object — moonboots, Nov 12 '20 at 17:52
@moonboots I have found the 2 buttons in Mass Dynamic and Animated, but I do not know how to use them. I'm a beginner and not familiar with the "keyframe" concept. Perhaps you could give me some hints to begin with. This specific question of mine is hard to seek in google which I would consult in other case. — user3357120, Nov 12 '20 at 17:59

moonboots · Accepted Answer · 2020-11-12T19:37:53.730

3

There might be another solution but I don't know it. So what you could do is:

Give your object a Rigid Body > Type > Active, create your slope, Type > Passive.
Put your object on the bottom, make sure it doesn't come across the surface, give your object a keyframe (i) > Location, Rotation and Scale, enable the Rigid Body > Animated option and give it a keyframe as well (put your mouse cursor over the option and press i):

Several frames later, move the cube a bit, create a second keyframe for your object, then disable the Animated option and keyframe again:

If the initial momentum is strong enough, it should work fine:

File:

edited Nov 12 '20 at 19:37

answered Nov 12 '20 at 18:22

moonboots

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I'm trying to understand what's going on here and sounds correct. Could you provide me with a .blend file ? – user3357120 Nov 12 '20 at 18:33
sure, I've edited my answer – moonboots Nov 12 '20 at 18:35
Good. Now I just want to make it moving. Where do I enable it as in your last picture ? There is missing the |> button at the bottom. – user3357120 Nov 12 '20 at 18:41
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spacebar to play, shift left arrow to go to frame 0 – moonboots Nov 12 '20 at 18:47
My cube falls down on the left without moving upwards to the right whenever I change something. Which parameter do I have wrong here ? – user3357120 Nov 12 '20 at 19:05
I don't know, maybe make sure that the cube doesn't touch the surface of the slope, if it still doesn't work, share your file: https://blend-exchange.giantcowfilms.com/ – moonboots Nov 12 '20 at 19:10
Please see here: I wanna move the cube more to the right, where can I change this ? – user3357120 Nov 12 '20 at 19:20
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as I said, make sure that the cube doesn't touch the surface of the slope, it's the problem here, the cube goes through the surface at frame 0 and 5 – moonboots Nov 12 '20 at 19:24
Right it works now. But when I press the "G" key for Grab and then press mouse the cube is not in the position I put it right now but in a previous one. How can I fix it ? – user3357120 Nov 12 '20 at 19:27
delete the keyframes you've created and re-keyframe correctly – moonboots Nov 12 '20 at 19:31
And yet, how can I create the horizontal green line between the 2 yellow dots indicating the seconds ? What this line means, when connecting the two points ? May it have a different color from green ? – user3357120 Nov 12 '20 at 19:37
it means that,- there are no transformations between keyframe 1 and 2 – moonboots Nov 12 '20 at 19:39
Where can I set this line to Green ? I have created an Orange one and the cube stays at rest. – user3357120 Nov 12 '20 at 19:41
oh ok you must be talking about the line that means that it has calculated the physics simulation, anyway you don't have to care about these lines – moonboots Nov 12 '20 at 19:43
Sorry to continue asking do you mind? Here, the cube doesn't move at all, why? – user3357120 Nov 12 '20 at 19:47
Let us continue this discussion in chat. – moonboots Nov 12 '20 at 19:49

initial velocity for a rigid body simulation: a ball rolling on a skew plane

1 Answers1