Player goes straight through walls despite CollisionPusher

#1

Hi,

I am currently testing simple collisions from my moving car (CollisionBox) and walls/obstacles (CollisionBox), using CollisionPusher.

So far, I have got the collisions working in the sense that the walls do push back against the player, and (kind of) stop it from moving, and allow me to slide along the wall. However, if I keep attempting to move forward, the player tunnels straight through the wall.

I have tried using pusher.setHorizontal(True) to prevent it from scaling the wall but this only prevented the object from moving over the wall, not straight through it.

How to I make sure the car does not magically end up on the other side of the wall? What am I doing wrong?

Key part of code:

# Model initialised and rendered to render as parent
colNode = model.attachNewNode(CollisionNode(nodeName))

# Wall Handling
# Initialise pusher collision handling
pusher = CollisionHandlerPusher()

pusher.addCollider(colNode, self.model, base.drive.node())
# pusher.addCollider(colNode, base.camera , base.drive.node())

pusher.addInPattern('%fn-in-%in')
pusher.addOutPattern('%fn-out-%in')

# Problem is the racecar will attempt to scale the wall
# Unfortunately still does not fix it
# TODO: Try http://www.panda3d.org/manual/?title=Rapidly-Moving_Objects
pusher.setHorizontal(True)

base.cTrav.addCollider(colNode, pusher)

Thank you!

#2

Hmm… Are you updating your car’s velocity on contact with the wall?

For one thing, it occurs to me that if your car’s velocity becomes too high, it might eventually more or less “teleport” to the other side by virtue of moving so fast that a single position-update moves it entirely to the other side of the wall.

I do note that you have the “rapidly-moving objects” page bookmarked there; the approach given there may well help.

However, the main thought in reducing the vehicle’s speed is that when one drives against a wall, one would expect the vehicle’s speed to decrease–and that decreased speed may help to keep the physics simulation stable.

[edit] Another thought: how are you updating your vehicle’s speed and position? Are you doing it in a task?

#3

Hi thanks for the reply!

I think you are right that the velocity becomes high. I note that the position of my player continues to get updated when my arrow keys which move the player are pressed, until it just teleports to the other side. Why is the pusher not negating this effect though?

Also, yes, I am using a task to update the car’s position.

To summarise, I am using a friction/acceleration based movement system. When the user presses up, the acceleration increases. When the user presses down, the acceleration decreases. An infinitely running task starts a movement function which updates the velocity and acceleration, and then positions, accordingly.

Strangely, I’m already setting the speed and accelerations to 0, in both the in and again events, but the car still teleports and tells me that the car’s position changes even though it is colliding with the wall.

What workaround do you suggest? And why does the Pusher event not “push” enough to counteract my movement. I have made my collision box insanely large, and it still moves through the box (this time without teleporting; it now moves smoothly through it).

#4

If I’m not much mistaken, the pusher doesn’t exert physical forces–all that it does is to attempt to prevent objects from intersecting. In short, it updates the position of the “from” object such that it’s no longer intersecting with the “into” object–and that’s it.

The expectation, I think, is that you handle velocity of the objects in question, including how the velocity should change in response to a collision.

Indeed, I imagine that your vehicle’s velocity is stored in a variable of your own; a Vec3 somewhere, perhaps. If so, then Panda’s collision system presumably doesn’t know about that variable, and thus isn’t in a position to alter it.

Okay, fair enough–that should be fine, I think.

Hmm… That is odd. Could I see the code for your “in”- and “again”- events, as well as the code in which you update your vehicle’s position and speed (the latter including the handling of friction and player input), please?

#5

Thank you for your help!

Yes it is. I realise that this might actually be a problem, because I am updating my own position via the x, y, z variables I am storing in my class, but these positions are not updated with the model’s position.

This might be the reason why I am visually seeing the model not moving but my internal (x,y,z) positions changing. I will try obtaining the positions from the model and increasing my velocity from the model’s x,y,z positions instead of my internal ones.

#6

Ah, yes–I think that may well be the source of your problem. What I think that I’ve usually done is pretty much what you suggest as a fix: the model (or, oftentimes, a “handle” NodePath above the model) holds the object’s position. I store the object’s velocity in a simple Vec3, and apply it to the relevant NodePath to update the position. If I want to access the model’s position, I retrieve it from the NodePath.

It’s seemed fairly reliable when I’ve used it, I believe!

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#7

Yep! I fixed it by using the positions retrieved from the NodePath instead of from my own object!

Thank you for your help!

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#8

Ah, excellent! I’m glad that you got it working, and the help is my pleasure. :slight_smile:

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