Rotating a model around an axis

Hello

I’m trying to rotate a model around an axis (windmill wings), here’s the model as imported without any change, the rotation works perfectly fine I define an angular velocity:
Image2

I defined a second node with the same height and used LookAt, it effectively turns the wings in the desired direction:
Image3

But then when I apply an angular velocity, the wings rotate around a point, going up and down. I tried to define a constraint but it move the second node, and if I make the second node body static (no mass), the model doesn’t move at all
Image5

Here’s the code I used:

                AnimatedModel* wheelObject = tileNode->CreateComponent<AnimatedModel>();
				wheelObject->SetModel(cache->GetResource<Model>("Models/WindMillWings.mdl"));
				wheelObject->SetCastShadows(true);
				wheelObject->SetMaterial(0, cache->GetResource<Material>("Materials/Windmill/Wood.xml"));
				wheelObject->SetMaterial(1, cache->GetResource<Material>("Materials/Windmill/Cloth.xml"));

				RigidBody * Body = tileNode->CreateComponent<RigidBody>();
				CollisionShape * Shape = tileNode->CreateComponent<CollisionShape>();
				//Shape->SetCylinder(0.25, 1.6,Vector3(0.5,0.0,0.0),Quaternion(90.0));
				Shape->SetSphere(1.0);
				Body->SetMass(0.1f);
				Body->SetGravityOverride(Vector3(0.0, 0.0, 0.0));
				Body->SetUseGravity(false);
				Body->SetLinearDamping(0.0f);
				Body->SetAngularDamping(0.0f);
				Body->SetAngularVelocity(Vector3(2.0, 0.0, 0.0));
				Body->SetCollisionLayer(1);

				Node * anchorNode = sceneGame_->CreateChild();
				anchorNode->SetPosition(Vector3(tileNode->GetPosition().x_ + 2.0, tileNode->GetPosition().y_, tileNode->GetPosition().z_ +5.0));
				RigidBody * anchorBody = anchorNode->CreateComponent<RigidBody>();
				CollisionShape * anchorShape = anchorNode->CreateComponent<CollisionShape>();
				anchorShape->SetSphere(1.0);
				anchorBody->SetMass(0.1f);
				anchorBody->SetUseGravity(false);
				tileNode->LookAt(anchorNode->GetPosition());
				
				Constraint* wingsConstraint = tileNode->CreateComponent<Constraint>();
				wingsConstraint->SetConstraintType(CONSTRAINT_HINGE);
				wingsConstraint->SetOtherBody(anchorBody);
				wingsConstraint->SetWorldPosition(tileNode->GetPosition());
				wingsConstraint->SetAxis(Vector3::UP);
				wingsConstraint->SetDisableCollision(true);

And the model:
https://ufile.io/s6hhx

I tried used a rotation attribute animation but I’ve got the same problem
It’s probably not that complicated but I’ve been trying to fix that for almost one day :sunglasses:
thanks

I found the following from Urho Samples and Documentation.

To Set rigid body rotation with rotation of speed 20, in world space.
Rigid Body->SetRotation(Quaternion(0.0f, 20* timeStep, 0.0f))
I could not see how to put the rotation in parent space from bullet.

To set rotation of node, with speed 20,
from billboards Sample line 302,
for world rotation,
lightNodes[i]->Rotate(Quaternion(0.0f, 20 * timeStep, 0.0f), TS_WORLD);
for local rotation,
lightNodes[i]->Rotate(Quaternion(0.0f, 20 * timeStep, 0.0f), TS_LOCAL);

Note: All these target only Y axis.

Try:

Body->ApplyTorqueImpulse(tileNode->GetRight() * smallFloat);

Instead of setting the angular velocity.

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I tried, but I’ve got the same behavior

Like @Eugene said, using a RigidBody for this purpose could be considered overkill. As long as there needn’t be any interaction with other objects.
I made a component using the same windmill model:

Because of the windmill model’s orientation, LookAt() behaves illogical. I think it would make more sense for it to spin around its Z axis (in Urho).

1 Like