Bounce?

Hi All,

I'm a complete noob - so much so that I have had to cross post this as I don't know what forum it should go in!

I'm starting on what I thought would be a simple project - a space hopper! You know - those big rubber orange balls you sit on and bounce.

So I made a big orange rubber ball and gave it physics - but there doesn't seem to be a bounce parameter in the prim dialog. Is this something I can set in script?

Or am I going to have to script detecting collisions and applying an impulse?

Thanks for listening - I'm the one in the sandbox standing looking at an orange ball for hours on end

Yes.

And when you figure out how to get land collisions to work sanely, post here.

You can give it some buoyancy using "llSetBuoyancy" which will make it bounce, somewhat.

Many thanks to Lightwave Valkyrie for IMing this script to me in game:

vector velocity = <0,0,0>; // Initialization 
float rebound = 1.50; // Rebound strength 

collide() 
{ 
    vector comparison = llGetVel(); 
    if(llVecMag(comparison) > 1) 
    { 
        if(llVecMag(llVecNorm(comparison) - llVecNorm(velocity)) > 1) 
            llApplyImpulse(llVecNorm(comparison) * llVecMag(velocity) * rebound * llGetMass(),FALSE); 
        else 
            llApplyImpulse(-1 * llVecNorm(comparison) * llVecMag(velocity) * rebound * llGetMass(),FALSE); 
    } 
} 

default 
{ 
    state_entry() 
    { 
        llCollisionSound("",0.0); 
        llSetTimerEvent(0.2); 
        llSetStatus (STATUS_ROTATE_X|STATUS_ROTATE_Y|STATUS_ROTATE_Z, FALSE);
        
    } 

    collision_start(integer total_number) 
    { 
        collide(); 
    } 
    land_collision_start(vector pos) 
    { 
        collide(); 
    } 
    timer() 
    { 
        velocity = llGetVel(); 
    } 
}

The question is - why does it work?

I naively thought that simply calling
llApplyImpulse(-1 * comparison * rebound * llGetMass(),FALSE);
in the event handler would do the job.

Is the velocity of the object in collision_start the velocity before or after the collision?
Why is there the need to NOT * -1 in some cases?

I suspect the answers may be that sometimes the object passes slightly through the ground and therefore is heading in the opposite direction when the event fires.

Any insights on this wierdness would be much appreciated.

Thanks