Collision Detection problems: Sphere passes through wall

Scripting Issues
1

Hi,

I am making my first game with Panda3D, it is a top down 2D shooter. My level consists of quads and each quad has a CollisionBox attached for collision detection. The player’s ship has a CollisionSphere attached:

self.collisionHandler = CollisionHandlerQueue()

self.ship = render.attachNewNode("ship")
self.ship.setTwoSided(True)
self.shipHeading = Vec3(0, 0, 0)
shipObject = loadObject("plane", "ship2", self.ship, depth=PlayerHeight, transparency=True)
self.setVelocity(self.ship, Vec3(0, 0, 0))
shipCollider = self.ship.attachNewNode(CollisionNode("player ship"))
        
shipCollider.node().addSolid(CollisionSphere(0,0,0, 1.0))
shipCollider.show()
self.collisionTraverser.addCollider(shipCollider, self.collisionHandler)

and

# tile is a NodePath
tileCollider = tile.attachNewNode(CollisionNode("wall (%i, %i)" % (x,y)))
tileCollider.node().addSolid(CollisionBox(Point3(0,0,0), 0.5, 0.5, 0.5))
tileCollider.show()

The result looks like this:

When moving the player it bounces usually off the walls, but sometimes it passes into or through the walls :frowning:

My collision handler, first method to respond to a collision:

traveledWay = self.getVelocity(self.ship)*dt
self.ship.setPos(self.ship.getPos() + traveledWay*-1.5)

The second one I tried:

self.setVelocity(self.ship, self.getVelocity(self.ship) * -1.0)

And the third one I took from the “Ball in Maze” sample:

reflectionVector = (normal * normal.dot(inVector * -1.0) * 2.0) + inVector

self.setVelocity(self.ship, reflectionVector * (currentSpeed * (((1-velocityAngle)*0.5)+0.5)))

disp = entry.getSurfacePoint(self.render) - entry.getInteriorPoint(self.render)
newPosition = self.ship.getPos() + disp
self.ship.setPos(newPosition)

All three methods show some problems, that sometimes the CollisionSphere passes through the walls.

Do you have any idea or suggestions what else I could try or what is wrong with my code?

Thank you,
Enrico

2

Have you considered using a CollisionHandlerPusher instead of doing the work yourself? The advantage to this is that the pusher already includes the (fairly complicated) logic to ensure that collisions work reliably 98% percent of the time.

David

3

I tried the demo from the manual with that Pusher and I am able to penetrate the static sphere in the demo deeply. So I decided against it. I will try again now :slight_smile:

4

I integrated the CollisionHandlerPusher and it is way better now :slight_smile:
However, with some trying the sphere can still pass through the boxes :frowning:

Edit: My ship is slowly moving, 5 units per second max. I am currently implementing the suggestions from: panda3d.org/manual/index.php/R … ng_Objects

Any more ideas?

5

No collision system can be perfect, but it should work the vast majority of the time. I’m not sure about boxes, though–the fact that they have two back-to-back faces (which might be closer together than the radius of your sphere) could be causing problems. Try using just one-sided CollisionPolygons, or making your boxes larger than your sphere.

David