The bullet rebound diagram is as follows:

1. Both walls and bullets are collisions.

2. Prerequisites: We need to know the bullet's forward direction vector and the wall's direction vector.

3. Calculate the simple process. Yellow is the bullet direction vector. Calculate the angle between the bullet and the wall. Calculate the orange direction vector according to the incident angle equal to the reflection angle. At this time, only the bullet direction has changed, and then the offset of position is calculated. According to the angle between the wall and the bullet itself, the offset is calculated by the trigonometric function sin/cos. The final effect is like the red arrow.

Code:

-- The bullet bounced back. ColliderObj: Collision wall has four sides. AmmoLength: Estimated bullet length,Remarks: self.Dir For the current direction vector of the bullet,self.o_Transform An example of a bullet,
function AmmoBase:ReflectBullet(ColliderObj, AmmoLength)

    local inNormal = nil
    local wallNormal = nil
    local XOrZ = true
    if tostring(ColliderObj.transform.name) == "ForwardWall" then
        inNormal = Vector3(0, 0, -1)
        wallNormal = Vector3(1, 0, 0)
        XOrZ = true
    elseif tostring(ColliderObj.transform.name) == "BackWall" then
        inNormal = Vector3(0, 0, 1)
        wallNormal = Vector3(1, 0, 0)
        XOrZ = true
    elseif tostring(ColliderObj.transform.name) == "LeftWall" then
        inNormal = Vector3(1, 0, 0)
        wallNormal = Vector3(0, 0, 1)
        XOrZ = false
    elseif tostring(ColliderObj.transform.name) == "RightWall" then
        inNormal = Vector3(-1, 0, 0)
        wallNormal = Vector3(0, 0, 1)
        XOrZ = false
    end
    if inNormal == nil then
        return
    end

    local wallAngle = Vector3.Angle(self.Dir, wallNormal)
    local reflexDir = Vector3.Reflect(self.Dir,inNormal)
    local dirAngle = 180 - Vector3.Angle(self.Dir, reflexDir)
    local dic = math.sin(math.rad(dirAngle)) * AmmoLength 
    
    -- log(tostring(wallAngle) .. "  Angle with wall")
    -- log(tostring(reflexDir) .. "  Correction vector")
    -- log(tostring(dirAngle) .. "  Reflection angle")
    -- log(tostring(dic) .. "  Position correction")

    local pos = self.o_Transform.position
    if XOrZ then
        if wallAngle > 90 then
            self.o_Transform.position = Vector3(pos.x - dic, pos.y, pos.z)
        else
            self.o_Transform.position = Vector3(pos.x + dic, pos.y, pos.z)
        end
    else
        if wallAngle > 90 then
            self.o_Transform.position = Vector3(pos.x, pos.y, pos.z - dic)
        else
            self.o_Transform.position = Vector3(pos.x, pos.y, pos.z + dic)
        end
    end
   
    self.Dir = reflexDir
    self.o_Transform.rotation = Quaternion.FromToRotation(Vector3.forward, self.Dir) -- Direction correction

end