Physics bug (falling through floor)

[Brutile]

I decided to make a mini golf game for the game tournament, but I'm being haunted by some physics bug. I have a ball that is 0.1 scale and after it gets hit, once it gets to a specific point, it falls throught the floor. It happens without fail. The hotspot seems to be in the middle of the CSG where the two triangles meet. Even when I scale the ball to 1, it doesn't fall through the floor, but it does hit a bump and put it off course.

 

Here's my script in case you can see anything that might be wrong.

 

Script.mouseSensitivity = 2.0
Script.camOffset = Vec3(0, 1, -3)
Script.camSmoothing = 10.0
Script.hitForce = 350
function Script:Start()
--initialize camera
self.camera = Camera:Create()
self.camera:SetFOV(70)
self.camera:SetRange(0.05, 1000)
self.camera:SetMultisampleMode((System:GetProperty("multisample", "4")))
self.camera:SetRotation(self.entity:GetRotation(true))
self.camera:SetPosition(self.entity:GetPosition(true) + self.camOffset)
--add listener as camera
self.listener = Listener:Create(self.camera)
--create player model
self.entity:SetPosition(self.entity:GetPosition(true) + Vec3(0, 0.1, 0), true)
self.model = Model:Sphere()
self.model:SetScale(0.1, 0.1, 0.1)
self.model:SetPosition(self.entity:GetPosition(true), true)
self.model:SetParent(self.entity)
self.model:SetColor(1,1,1)
--setup ball physics
self.entity:SetMass(1)
self.entity:SetFriction(0.1, 0.1)
self.entity:SetSweptCollisionMode(true)
--Create a shape
local shape = Shape:Sphere(0,0,0, 0,0,0, 0.1,0.1,0.1)
self.entity:SetShape(shape)
shape:Release()
--set collision type of player
self.entity:SetCollisionType(Collision.Prop)
local window = Window:GetCurrent()
local context = Context:GetCurrent()
window:SetMousePosition(Math:Round(context:GetWidth() / 2), Math:Round(context:GetHeight() / 2))

self.mouseDifference = Vec3(0, 0, 0)
self.camRotation = Vec3(0, 0, 0)
self.camera:SetRotation(self.camRotation)
end
function Script:UpdateWorld()
local window = Window:GetCurrent()
local context = Context:GetCurrent()
--mouse look
self.currentMousePos = window:GetMousePosition()
window:SetMousePosition(Math:Round(context:GetWidth() / 2), Math:Round(context:GetHeight() / 2))
self.currentMousePos.x = Math:Round(self.currentMousePos.x)
self.currentMousePos.y = Math:Round(self.currentMousePos.y)
self.mouseDifference.x = Math:Curve(self.currentMousePos.x - Math:Round(context:GetWidth() / 2), self.mouseDifference.x, 3)
self.mouseDifference.y = Math:Curve(self.currentMousePos.y - Math:Round(context:GetHeight() / 2), self.mouseDifference.y, 3)
self.camRotation.x = Math:Clamp(self.camRotation.x + self.mouseDifference.y / self.mouseSensitivity, 0, 70)
self.camRotation.y = self.camRotation.y + (self.mouseDifference.x / self.mouseSensitivity)
--camera orbit around ball
self.camera:SetRotation(self.camRotation)
self.camera:SetPosition(self.entity:GetPosition(true), true)
self.camera:Move(self.camOffset)
--hit the ball
if window:MouseHit(1) then
 local c = self.camera:GetPosition(true)
 local p = self.entity:GetPosition(true)
 local dir = p - Vec3(c.x, p.y, c.z)
 dir = dir:Normalize() * self.hitForce
 self.entity:AddForce(dir)
end
end

 

All I did was create a new map, added a pivot at 0,0,0 with this script assigned, then created a CSG cube at pos: 0, -16, 2688 and size: 512cm, 32cm, 5888cm.

Hit the ball without moving the mouse and it will get half way down and fall through.

I even tried a small 512x512 floor with walls and just hit it around. Eventually it would fall through.

[AggrorJorn]

Thats sound like same issue I was having when I made my minigolf game couple years ago. Physics accuracy for the ball were attrocious. After a lot of fumbling about I gave up.

The ball seemed to be filled with water or something, it would roll straight for a while and then all of the sudden it would roll in to a different direction. This mostly happened when slowing down.

 

Things to try (which some of you already have):

1. Swept collision on ball and level geometry
    
   
2. Setting a higher physics resolver interval
    
   
3. instead of a csg sphere, using a model with a different physics shapes, going from relatively basic, to extreme high polycount (for a ball).
    
   
4. Larger model/csg sphere instead of the tiny scale you are using now.
   

[Brutile]

Thanks, I'll try those

[Brutile]

Unfortunately, those didn't work.

 

I'm convinced there's a correlation between the ball falling through and the seam where the two trianges meet to create the polygon of the surface.

[AggrorJorn]

You can experiment with the hollow csg brush function to get more triangles accross the surface. Then you will start to see even more inaccuracies.

[Brutile]

Yep. Put a whole bunch of smaller boxes and it's like one of those car testing tracks (but flat). The ball just gets stuck on them.

[Josh]

It is possible you might get better results with a larger ball. You would need to make everything in your level larger, of course.

 

I would like to see a demo of this in action.

 

Jorn, without having the framerate displayed it is difficult to tell what is happening there.

[Brutile]

I recorded a short demo of what is happening. I also enabled wireframe so you can see what I mean about the seam between the triangles.

 

[Josh]

I actually do think I know how this can be improved.