I don’t really know any other plugins, but I usually try to rig them manually. Rigging them manually is not that hard, actually. You will need to use Motor6D’s and welds, although welds are not necessary. Motor6D’s create a movable joint between two parts. Every Motor6D has a Part0 and Part1 property. Part1 will be connected to Part0
First off, every rig needs a Humanoid and a HumanoidRootPart. Giving a part that exact name will assign the humanoid’s rootpart to the part. You’ll then need to connect the HumanoidRootPart to a “main” part of the rig, just like the torso of r6 characters and the lower torso of r15 characters, via a Motor6D. That joint will be the RootJoint of the humanoid.
Every Motor6D has a C0 and C1 property that determines its position. C0 is a relative cframe from the Part0, which means that C0 is a certain distance away from Part0’s CFrame. C1 is subtracted from the C0 to determine the final offset point for Part1. Just like welds, Motor6D’s alter the parts’ positions so that: part0.CFrame * C0 == Part1.CFrame * C1
I wrote this function that makes it easy to connect two parts via a Motor6D or weld and will automatically adjust their C0 and C1 (a bit of scripting knowledge is required):
local function Connect(isMotor, p0, p1, name, parent)
local m = Instance.new(isMotor and "Motor6D" or "Weld")
local C = CFrame.new(p0.Position)
m.C0 = p0.CFrame:inverse() * C
m.C1 = p1.CFrame:inverse() * C
m.Name = name
m.Parent = parent
end
-- Example: (For the first argument, the Boolean (the true value there), putting "true" will create a Motor6D, putting "false" will create a Weld.
Connect(true, rig.HumanoidRootPart, rig.Torso, "RootJoint", rig.HumanoidRootPart)
On the topic of welds, welds created a fixed joint between two parts and have the same properties as Motor6D’s: Part0, Part1, C0, C1. You can use welds when you attach a part to a movable part and you cannot move that part. They aren’t really necessary when you’re rig building, but they can help you.
After all of that, you’ll be able to animate your own custom rig with any animation editor