Simulate Spring scaling the object

[telmopereira]

Hi everybody,

I am trying to simulate the behavior of a spring in my application. My idea was: when i make force on the object that is a spring, i scale the object...graphically that part is easy. But i don't know how to do that physically with Newton...there is some way to scale in one axis the physic object ?

Thanks,
Telmo

[JernejL]

well, you can scale a newton object with a convex hull modifier.

[telmopereira]

How exactly ?

By doing NewtonConvexHullModifierSetMatrix ?

[JernejL]

yes, that function exactly, you can set scaling there.

[Carli]

Seems to me that most of the newton newbies don't know what a matrix is.
I can give you a hint: use Wiki http://en.wikipedia.org/wiki/Matrix_(mathematics)

[telmopereira]

Hi,

I try to use the NewtonConvexHullModifier, but something is wrong.
When i am creating an hull collision, i did something like this:

Code: Select all

collision = NewtonCreateConvexHull(p_world, totalVertices, cloud, sizeof(dFloat)*3, 20, shapeId, NULL);
collModifier = NewtonCreateConvexHullModifier(p_world,collision,shapeId);

body = NewtonCreateBody(p_world, collModifier);
NewtonReleaseCollision(p_world, collModifier);



Then, when i do something like setPosition of the object, i do something like this:

Code: Select all

matrix4 mat;
NewtonBodyGetMatrix(p_body, mat.pointer());
mat.setTranslation(pos);
if(strcmp(getExpType().c_str(), "spring") ==0)
   NewtonConvexHullModifierSetMatrix(ApplicationManager::sprExp->collMod,mat.pointer());   
else
        NewtonBodySetMatrix(p_body, mat.pointer());


The problem is if i use the NewtonConvexHullModifierSetMatrix instead of NewtonBodySetMatrix, the object is just represented graphically, there are no collisions...it's like object is not there.
I think that is because with the NewtonBodySetMatrix it's told to Newton which body will have that matrix, and in HullModifier, is not told which body will be affected... is that the problem ? Someone knows how to solve this?

Thanks,
Telmo

[JernejL]

ofcourse there will be no collisions from just that, if you are going to move objects manually that's not the way newton is intended to be used. use newtonupdate and look at some tutorials.