Irrlicht Engine

Posted: **Wed Aug 15, 2007 10:58 am**

BableOff wrote:Updated solution.

void faceTarget(irr::core::vector3df targetPos) {
  core::vector3df nodePos = targetPos - myNode->getPosition();
  myRotation.Y = atan(nodePos.Z/nodePos.X) * (180.0f / irr::core::PI);
  if((targetPos.X - myNode->getPosition().X) > 0) {
    myRotation.Y = 90 - myRotation.Y;
  } else if((targetPos.X - myNode->getPosition().X) < 0) {
    myRotation.Y = -90 - myRotation.Y;
  }
  myRotation.Y -= 90;
  myNode->setRotation(myRotation);
}

almost exactly what i was looking for, now all i need is it to follow the camera when you move up down?

Posted: **Tue Dec 04, 2007 6:15 pm**

How do I use "faceTarget", node->faceTarget(thetarget);?

Posted: **Mon Jan 07, 2008 7:13 pm**

I modified it a little

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irr::core::vector3df faceTarget(irr::core::vector3df targetpos, irr::core::vector3df nodepos) { 

  core::vector3df nodePos = targetpos - nodepos; 
  float degree = atan(nodePos.Z/nodePos.X) * (180.0f / irr::core::PI); 
  if((nodepos.X - targetpos.X) > 0) { 
   degree = 90 - degree; 
  } else { 
    degree = -90 - degree; 
  } 
  if (nodePos.X==0.f) 
  {
	  return (vector3df(0,0,0));
  } 
  else 
  { 
	  return (vector3df(0,(float) degree, 0));
  }
  }

using it is simple

Code: Select all

node->setRotation(faceTarget(target->getPosition();node->getPosition());

Posted: **Tue Mar 11, 2008 2:25 am**

Code: Select all

void Actor::faceTarget(core::vector3df tpos)
{
	core::vector3df diff = tpos - actorNode->getAbsolutePosition();
	diff.normalize();
	
	if (tpos.X != 0.0f || tpos.Y != 0.0f) {
		f32 newYaw = atan2(diff.X, diff.Z);
		yaw = newYaw * core::RADTODEG;
	}
	
}

I have another process that smoothly transitions from yaw to the node's current rotation. Alls I did was take the atan2 of (diff.X, diffZ)...

ActorNode and yaw belong to the Actor class. To do something simular to the above code it would look like this:

Code: Select all

irr::core::vector3df faceTarget(irr::core::vector3df targetpos, irr::core::vector3df nodepos) {

  core::vector3df posDiff = targetpos - nodepos;
  f32 degree = nodepos.Y; //keep current rotation if nothing to do
  posDiff.normalize();

  if (posDiff.X != 0.0f || posDiff.Z != 0.0f)
    degree = atan2(posDiff.X,posDiff.Z) * core::RADTODEG;

  return core::vector3df(0,degree,0);
}

Posted: **Mon Jun 23, 2008 2:32 pm**

I just spent... too many hours trying to get one node to face another node in 3d space. Specifically, I have one spaceship controlled by the AI, which has to turn and fire on the player's ship. Being a space-flight game, there is no ground, and no real sense of "up" to speak of. The spaceship has to rotate through all three axes, not just the Y axis.

By sheer accident (I'm horrible at math) I finally discovered how to do this using Irrlicht without really having to do all that math. Hopefully this will save someone else the trouble I went through.

Code: Select all

            // rotate to face target Node
            vector3df nodePos = node->getPosition();
            vector3df targetPos = targetNode->getPosition();
            vector3df diff = targetPos - nodePos;
             
            node->setRotation(diff.getHorizontalAngle()); 
            node->updateAbsolutePosition();

Edit: I just noticed in the Irrlicht Documentation under this function it says "Thanks to Arras on the Irrlicht forums to add this method." Thanks man :-)

Posted: **Thu Feb 12, 2009 8:04 am**

wow man.. that code save me a lot.. thanks..

Posted: **Mon Mar 09, 2009 1:18 am**

Never Mind this miss post...

Posted: **Mon Sep 20, 2010 10:36 pm**

facetarget function is very useful to help me . thanks

Irrlicht Engine

Rotate a Node, face another node