imtrobin

05-12-2006 15:51:44

Hi,

I noticed that PhysX uses 1 unit = 1 m, which I find to be small. My world scale uses 1 unit = 1 cm, and basing on tutorial 1, I'm trying to find a formula to calculate the force.

I change the cube shape to 100, and gravity to 980.

I used the density as iron which is 7850 kg/m3 or 0.07850 kg/cm3. So the mass = density * volume = 0.00785*100*100*100 = 7850 kg.

So F = ma, means to accelerate 1m/s2, I would need to have a force of

7850 x 100 cm/s2 = 785, 000 N. However, when I use addForce with that, the box doesn't even budge. I need to use a force of 7,850,000 to get the box to move.

So is there a right way to calculate the force? And what is the "correct" range of values for the density/mass?

I noticed that PhysX uses 1 unit = 1 m, which I find to be small. My world scale uses 1 unit = 1 cm, and basing on tutorial 1, I'm trying to find a formula to calculate the force.

I change the cube shape to 100, and gravity to 980.

// Tutorial 1

mScene->hasGravity (Vector3 (0,-980,0));

mCube = mScene->createBody ("testcube" ,"box.mesh"

,new nxOgre::cubeShape (100.0f ,0.00785 , Vector3 (0,200,0));

I used the density as iron which is 7850 kg/m3 or 0.07850 kg/cm3. So the mass = density * volume = 0.00785*100*100*100 = 7850 kg.

So F = ma, means to accelerate 1m/s2, I would need to have a force of

7850 x 100 cm/s2 = 785, 000 N. However, when I use addForce with that, the box doesn't even budge. I need to use a force of 7,850,000 to get the box to move.

So is there a right way to calculate the force? And what is the "correct" range of values for the density/mass?