This is normal behaviour. the pointtangent is not giving a circular force/vector (that doesn’t exist) – it’s a straight vector, that is tangent to the circle. So at each simulation step, the particle gets moved a bit, away from the circle in a tangent direction. At the next step it gets the new tangent vector, which pulls it largely back in line and makes it move “roughly” in the circle.
Depending on the speed and the amount of steps in the simulation, the particle will describe the circle very precisely (and thus pretty much staying on it) or less precisely (and thus each time getting off the circle and ending up describing a larger circle.) With a slow speed it’s a non-issue. With a higher speed you can try more steps in the simulation. But you’re probably better off adding a force pulling towards the center of the circle to compensate for the radius getting larger. (vector between self pointposition and the center of the circle, multiply it by scalar and add to the pointtangent and then set velocity) now tweak the scalar in “multiply by scalar” to find the amount needed to remain on the circle exactly. From: gareth bell Sent: Saturday, December 06, 2014 3:42 PM To: softimage@listproc.autodesk.com Subject: ICE: Speed, Velocity and circular motion Hi guys, Having an issue getting my head around this. I think I want to use the formula for circular motion on this one. I've got some particles moving around in a circular motion with their velocity determined by a circular curve. Using circle>closest location>pointtangent>set velocity. This works great however it's not moving the buggers fast enough. if I multiply it by a scalar it speeds up but the circle radius increases which is correct according to the maths, however, I don;t want this to happen. I want to keep closely to the circle radius but simple speed up the particles moving around it. Any ideas? G
