View Full Version : Little exercise with Reactor
01-08-2005, 08:42 PM
Here's a simply exercise with Reactor on 3ds Max (refer to my attached jpg).
In A you can see the terms of the simulation: a sphere on a plane box (both included in a Rigid Body Collection).
What I want to simulate is shown in B: the plane box rotates around its centered pivot (keyframe animation), the ball follows the inclination and falls at the end of the box (reactor animation).
i've tried many changes but what I always obtained is shown in C: when the plane box starts rotating the ball passes through the box and falls down. (At the starting frame the ball and the box have no points in common. The distance is reduced to the closest value according with the Tollerance value)
Where I'm wronging?
Thanx in advance!
02-08-2005, 08:30 AM
Ok...a few things to keep in mind that may solve the problem. First, both objects have to be in the same set of solids. Second, the box has to be set to "unyielding" in the reactor object properties. Also, the ball shouldn't be touching the box at the beginning of the simulation...its should be moved away a little. This has to do with the collision tolerance of reactor. In top, far right of the screen, there is a tab with a little hammer on it...this is the utilities tab. Under it, there should be a button labelled "reactor". In that menu, under the "World" Tab, there is a collision tolerance setting. The smaller you set it, the closer you can place objects without reactor thinking they are colliding. But setting it smaller also drastically slows down the simulation.
02-08-2005, 11:52 AM
Hi Buzzy, thanx fo your interest in my little touble with reactor.
... Yes, I obtained my bad simulation (C) with the box set as unyelding, no points in common or overlap where the ball stands over the box and trying many settings in Scale and Tollerance. It seems that the ball couldn't stay on the rising part of the box. In a while from the simulation start the ball intersects the box and falls through it. Increasing tollerance level just add a small delay to the same result (+ some unrealistic effects such as levitation and bouncing).
What you mean with: "...both objects have to be in the same set of solids"?
02-08-2005, 08:50 PM
By same set of solids, I mean, when you make a Solid Body Collection, both objects have to be in the same collection.
The box's mass should be set to zero also.
03-08-2005, 12:01 PM
Both the box and the sphere are in the same RBC, and I ran the simulation with the box mass set at 0,1,2,3.... always the same result.
But now I think to have a working solution: it seems that a RBC is not enough. The Box must be in a Deformable Mesh Collection; This allows the program to read its keyframed trasformations and put them in the simulation.
Don't know if there're other solutions.
03-08-2005, 12:44 PM
How many subdivisions does the box have? The solution gets more accurate if you do a 4x4x4 box then if you do a 1x1x1 box. You might want to try that. You shouldn't have to have a deformable mesh for something like this.
03-08-2005, 10:43 PM
another thing, for keyframe animation to work, I do believe that the animation needs to start before the simulation does on the timeline. In other words, move the keyframes back so the first one is below zero.
04-08-2005, 12:12 PM
I tried the box at 1x1x1. 4x4x4, 10x10x10, 20x20x20... nothing changed.
I also made many test changing all the pharameters on the simulation preview window (keyfr. subdivison... etc.): it seems that, at the moment, adding a Deformable Mesh Coll. is the only way to solve this task.
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