Facing opposite direction using lookAt

Scripting Issues
1

Hello!

I’ve been using Panda3D for two days, and I’m really enjoying it. I’m coding a simple game just to try some things, using some models in the Downloads section (ralph and the T-Rex)

Right now I have Ralph running around, something similar to the roamingRalph demo. I wanted a T-Rex to chase him, so I just added a second actor with the T-Rex model and then I tried a lookAt(ralph.getPos()) so it faced Ralph in a move task.

class TRex( DirectObject ):
    def __init__( self ):          
        self.trex = Actor("models/T-Rex/trex",
                            {"run":"models/T-Rex/trex-run"})
        
        self.trex.reparentTo(render)        
        self.trex.setPos(0, -80, 0)
        
        self.trex.loop("run")
        
        taskMgr.add(self.move,"moveTaskTRex")
        
    #Controls movement on each frame
    def move(self, task):
        
        self.trex.lookAt(ralphObject.ralph.getPos())        
    
        return Task.cont

But the T-Rex always faces exactly the opposite direction, as if running away from ralph. I also tried lookAt(ralphObject.ralph). Is it something in the model, like being the head in the negative Y, instead of the tail?

Thanks in advance!

2

Yes, that’s right, that model was modeled backwards. What can you do, most of those models were created by inexperienced students.

I’m pretty sure there’s a handy function that does what you want (ie, “lookAt, backwards.”) I just can’t for the life of me find it.

3

Until someone finds the simple answer, you can do the following:

Create a parent node for your T-Rex and reparent the T-Rex model to it.
Then rotate the T-Rex model by 180°
After that apply every other transform to the parent node.

So the altered code could look like this:

class TRex( DirectObject ):
    def __init__( self ):         
        self.trexParent = render.attachNewNode('trex-parent')
        self.trex = Actor("models/T-Rex/trex",
                            {"run":"models/T-Rex/trex-run"})
       
        self.trex.reparentTo(self.trexParent)       
        self.trex.setHpr(180° on the right axis)

        self.trexParent.setPos(0, -80, 0)
       
        self.trex.loop("run")
       
        taskMgr.add(self.move,"moveTaskTRex")
       
    #Controls movement on each frame
    def move(self, task):
       
        self.trexParent.lookAt(ralphObject.ralph.getPos())       
   
        return Task.cont
4

i have a similar problem with my art assets … but mine also have inverted normals and wrong scale so using setScale(.001,.001,-.001) makes them face right be correct scale and have correct normals :slight_smile:

5

Thank you for the answers! I’ll use Legion’s solution until I have my own models :slight_smile: