[Resike]

I put every fuction together now.

Alt + LeftClick - Move frame
LeftClick + horizontal/vertical mouse movement - Tilt X, Tilt Z
RightClick + horizontal/vertical mouse movement - Move Y, Move Z
Alt + RightClick + vertical mouse movement - Move X
MiddleClick + horizontal mouse movement - Rotate
MouseWheel - Zoom camera (0.1)
Ctrl + MouseWheel - Zoom camera (0.5)
Alt + MouseWheel - Zoom camera (1)

Alt + MiddleMouse - Reset to default

Only Y Tilting is missing atm.

local format, math, pi, halfpi = format, math, math.pi, math.pi / 2
 
local frame = CreateFrame("Frame", nil, UIParent)
frame:SetPoint("Center")
frame:SetSize(512, 512)
frame:SetBackdrop({bgFile = "Interface\\Tooltips\\UI-Tooltip-Background", insets = {left = 0, top = 0, right = 0, bottom = 0}, tile = true,})
frame:SetBackdropColor(0, 0.4, 0, 1)
frame:SetMovable(false)
 
local model = CreateFrame("PlayerModel", nil, frame)
model:SetModel("Creature\\Alexstrasza\\LadyAlexstrasa.m2")
model:SetAllPoints(frame)
model:SetSize(512, 512)
model:SetMovable(false)
model:EnableMouse(true)
model:EnableMouseWheel(true)
 
local function OnDragStart(self)
    self:SetMovable(true)
    self:StartMoving()
end
 
local function OnDragStop(self)
    self:StopMovingOrSizing()
    self:SetMovable(false)
    local x = math.floor(self:GetLeft() + (self:GetWidth() - UIParent:GetWidth()) / 2 + 0.5)
    local y = math.floor(self:GetTop() - (self:GetHeight() + UIParent:GetHeight()) / 2 + 0.5)
    self:ClearAllPoints()
    self:SetPoint("Center", x, y)
end
 
local function OnUpdate(self, elapsed)
    local x, y = GetCursorPosition()
    local pitch = model.pitch + (y - self.y) * pi / 256
    local limit = false
    if pitch > halfpi - 0.05 or pitch < - halfpi + 0.05 then
        limit = true
    end
    if limit then
        local rotation = format("%.0f", math.abs(math.deg(((x - self.x) / 64 + self:GetFacing())) % 360))
        if rotation ~= format("%.0f", math.abs(math.deg(self:GetFacing()) % 360)) then
            self:SetRotation(math.rad(rotation))
        end
    else
        local yaw = self.yaw + (x - self.x) * pi / 256
        self:SetOrientation(self.distance, yaw, pitch)
    end
    self.x, self.y = x, y
end
 
local function RightButtonOnUpdate(self, elapsed)
    local x, y = GetCursorPosition()
    local px, py, pz = self:GetPosition()
    if IsAltKeyDown() then
        local mx = format("%.2f", (px + (y - self.y) / 64))
        if format("%.2f", px) ~= mx then
            self:SetPosition(mx, py, pz)
        end
    else
        local my = format("%.2f", (py + (x - self.x) / 64))
        local mz = format("%.2f", (pz + (y - self.y) / 64))
        if format("%.2f", py) ~= my or format("%.2f", pz) ~= mz then
            self:SetPosition(px, my, mz)
        end
    end
    self.x, self.y = x, y
end
 
local function MiddleButtonOnUpdate(self, elapsed)
    local x, y = GetCursorPosition()
    local rotation = format("%.0f", math.abs(math.deg(((x - self.x) / 84 + self:GetFacing())) % 360))
    if rotation ~= format("%.0f", math.abs(math.deg(self:GetFacing()) % 360)) then
        self:SetRotation(math.rad(rotation))
    end
    self.x, self.y = x, y
end
 
local function OnMouseDown(self, button)
    if button == "LeftButton" then
        if IsAltKeyDown() then
            OnDragStart(frame)
        else
            self.x, self.y = GetCursorPosition()
            self:SetScript("OnUpdate", OnUpdate)
        end
    elseif button == "RightButton" then
        self.x, self.y = GetCursorPosition()
        self:SetScript("OnUpdate", RightButtonOnUpdate)
    elseif button == "MiddleButton" then
        if IsAltKeyDown() then
            self:Reset()
        else
            self.x, self.x = GetCursorPosition()
            self:SetScript("OnUpdate", MiddleButtonOnUpdate)
        end
    end
end
 
local function OnMouseUp(self, button)
    OnDragStop(frame)
    if button == "LeftButton" then
        self:SetScript("OnUpdate", nil)
    elseif button == "RightButton" then
        self:SetScript("OnUpdate", nil)
    elseif button == "MiddleButton" then
        self:SetScript("OnUpdate", nil)
    end
end
 
local function OnMouseWheel(self, delta)
    local zoom = 0.1
    if IsControlKeyDown() then
        zoom = 0.5
    elseif IsAltKeyDown() then
        zoom = 1
    end
    local distance = model.distance - delta * zoom
    if distance > 40 then
        distance = 40
    elseif distance < zoom then
        distance = zoom
    end
    self:SetOrientation(distance, model.yaw, model.pitch)
end
 
function model:SetOrientation(distance, yaw, pitch)
    if self:HasCustomCamera() then
        self.distance, self.yaw, self.pitch = distance, yaw, pitch
        local x = distance * math.cos(yaw) * math.cos(pitch)
        local y = distance * math.sin(- yaw) * math.cos(pitch)
        local z = (distance * math.sin(- pitch))
        self:SetCameraPosition(x, y, z)
    end
end
 
local x, y, z, px, py, pz, rot
 
function model:Reset()
    self:SetCustomCamera(1)
    self:SetCameraPosition(x, y, z)
    self:SetPosition(px, py, pz)
    self:SetRotation(rot)
    self:SetCameraTarget(0, 0, pi / 5)
    self:SetOrientation(math.sqrt(x * x + y * y + z * z), - math.atan(y / x), - math.atan(z / x))
end
 
function model:Initialize()
    self:SetCustomCamera(1)
    x, y, z = self:GetCameraPosition()
    px, py, pz = self:GetPosition()
    rot = self:GetFacing()
    self:SetCameraTarget(0, 0, pi / 5)
    self:SetOrientation(math.sqrt(x * x + y * y + z * z), - math.atan(y / x), - math.atan(z / x))
end
 
model:SetScript("OnKeyUp", OnKeyUp)
model:SetScript("OnDragStart", OnDragStart)
model:SetScript("OnDragStop", OnDragStop)
model:SetScript("OnMouseDown", OnMouseDown)
model:SetScript("OnMouseUp", OnMouseUp)
model:SetScript("OnMouseWheel", OnMouseWheel)
 
model:Initialize()

I think it's quite lightweigth but optimizations can always be done.