Cloth Simulation, and as a 'Physics Lab' test

Code Sharing
1

As I have mentioned in other posts, I have been working through (copies of) the Cloth Simulation and Physics Lab example projects. My notes on the former are added to the wiki here.

The code below does something similar to Cloth Simulation, as a new ‘Test 11’ for the Physics Lab, replacing the constraints by ‘soft’ DISTANCE joints:


Test11 = class()

function Test11:init()
    self.title = "Cloth simulation (use the accelerometer)"
    self.freq = 10  -- Softness of all distance joints (constraints)
    self.damp = 0.5 -- Damping for all distance joints
end

function Test11:setup()
    local b = {}
    for y = 0, 10 do
        for x = 0, 10 do
            local i = (y * 11) + x
            b[i] = createCircle(120 + x * 40, 600 - y * 40, 5)
            if y == 0 then b[i].type = STATIC end
        end
    end
    for y = 0, 9 do
        for x = 0, 9 do
            local i = (y * 11) + x
            local ir = i + 1
            local ib = i + 11
            local ibr = ib + 1
            local j = physics.joint(DISTANCE, b[i], b[ir],
                b[i].position, b[ir].position)
            j.frequency = self.freq
            j.dampingRatio = self.damp
            debugDraw:addJoint(j)
            j = physics.joint(DISTANCE, b[i], b[ib],
                b[i].position, b[ib].position)
            j.frequency = self.freq
            j.dampingRatio = self.damp
            debugDraw:addJoint(j)
            j = physics.joint(DISTANCE, b[i], b[ibr],
                b[i].position, b[ibr].position)
            j.frequency = self.freq
            j.dampingRatio = self.damp
            debugDraw:addJoint(j)
        end
        local ix = 10 * 11 + y -- Use 'y' to index x positions, here,
                               -- to save another for...end loop.
        local ixr = ix + 1
        local iy = y * 11 + 10
        local iyb = iy + 11
        local j = physics.joint(DISTANCE, b[ix], b[ixr],
            b[ix].position, b[ixr].position)
        j.frequency = self.freq
        debugDraw:addJoint(j) 
        j.dampingRatio = self.damp       
        j = physics.joint(DISTANCE, b[iy], b[iyb],
            b[iy].position, b[iyb].position)
        j.frequency = self.freq
        j.dampingRatio = self.damp
        debugDraw:addJoint(j)        
    end
end    
    
function Test11:draw()
end

function Test11:touched(touch)
end