AddForce question

[aiaf]

Initial model position:

Vec3(1, 2, 0)

TargetDirection vector:

Vec3(1, 4, 0)

 

When model arrives at certain position i want to send it back the same way.

Force is applied:

model->AddForce(targetDirection[0], targetDirection[1], targetDirection[2], true);

 

if (model->GetPosition(true).DistanceToPoint(Vec3(targetDirection[0], targetDirection[1], targetDirection[2])) < 0.2 && back == false) {
       model->SetVelocity(Vec3(0), true);
       model->AddForce(targetDirection.Inverse(), true);
       back = true;
   }

   if (model->GetPosition(true).DistanceToPoint(startPosition) < 0.2 && back == true) {
       model->SetVelocity(Vec3(0), true);
       model->AddForce(targetDirection, true);
       back = false;
   }

 

I expected this to work and have the box bouncing between the 2 points.

If i set condition for distance to be < 0.5 will work, but not with 0.2 value.

 

I dont understand why this happens, is something wrong with the way i do AddForce ?

sorry if this will be stupid question but dont know what i can do

[macklebee]

You are evaluating a force vector against a Vec3 position based on the distance between their respective Vec3 values? Seems like there would be a lot of things that could affect the outcome on whether or not this worked correctly. Since the model is a physics object, it can be affected by other physics forces in the scene which could make the distance check fail.

 

What are you setting the mass of the model to since that will affect how far your force (targetDirection) will move it? Also, the inverse of targetDirection is Vec3(-1,-4,0) which when used as a force will try to force the model down and to the negative X axis. Since it is a physics object, I assume the model is sitting on the ground so a negative Y force will not work.

 

If you are really wanting to use a physics object then i would try a more generic approach for alternating the force values without looking at positions.

example:

window = Window:Create()

context = Context:Create(window)

world = World:Create()

camera = Camera:Create()

camera:SetPosition(0,2,-4)

camera:SetRotation(0,0,0)

light = DirectionalLight:Create()

light:SetRotation(35,35,0)

 

ground = Model:Box(10,1,10)

ground:SetColor(0,1,0)

shape = Shape:Box(0,0,0, 0,0,0, 10,1,10)

ground:SetShape(shape)

ground:SetCollisionType(Collision.Scene)

ground:SetPosition(0,-0.5,0)

shape:Release()

 

model = Model:Box()

model:SetColor(1,0,0)

model:SetPosition(0,0.5,0)

shape = Shape:Box(0,0,0, 0,0,0, 1,1,1)

model:SetShape(shape)

model:SetCollisionType(Collision.Prop)

shape:Release()

model:SetMass(1)

 

Force = Vec3(100,400,0)

back = true

time = Time:Millisecs()

 

while window:KeyDown(Key.Escape)==false do

if window:Closed() then break end

 

if Time:Millisecs() > time + 1000 then

if back == true then

model:AddForce(Force, true)

back = false

else

model:AddForce(Vec3(Force.x*-1,Force.y,Force.z), true)

back = true

end

time = Time:Millisecs()

end

 

Time:Update()

world:Update()

world:Render()

context:Sync(true)

end

 

If you are just trying to accomplish a bouncing back and forth object, maybe an animated object would suit your needs better?

[aiaf]

The model is not sitting on the ground, can go in any direction,

 

model->SetMass(0.09);

model->SetGravityMode(false);

 

Model need to arrive to another entity that is moving , may encounter moving obstacles that will try to avoid.Then need to come back to the original position.

Thats why i tried to use physics, then most basic step is what i tried with distances.

 

Guess i could try with animated objects and have some kind of graph to create dynamically paths that wont intersect each other.

[aiaf]

I used PhysicsSetPosition to do the forward/back animation.

 

if(forward)
   model->PhysicsSetPosition(targetPosition.x, targetPosition.y, targetPosition.z, 0.01);
if(!forward)
   model->PhysicsSetPosition(startPosition.x, startPosition.y, startPosition.z, 0.01);

if (forward && model->GetPosition(true).DistanceToPoint(targetPosition) < 0.05) {
   forward = false;
}
if (!forward && model->GetPosition(true).DistanceToPoint(startPosition) < 0.05) {
   forward = true;
}