quantum/gamemode/engine/lib/client/cl_cinematic.lua

--    __           _        _______        _      __   
--   / /     /\   | |      |__   __|      | |     \ \  
--  / /     /  \  | |_ __ ___ | | ___  ___| |__    \ \ 
-- < <     / /\ \ | | '_ ` _ \| |/ _ \/ __| '_ \    > >
--  \ \   / ____ \| | | | | | | |  __/ (__| | | |  / / 
--   \_\ /_/    \_\_|_| |_| |_|_|\___|\___|_| |_| /_/  

                Quantum.Client.Cam = {}

function Quantum.Client.Cam.InvertAngle( ang ) return Angle( -ang.x, ang.y, -ang.z ) end -- Flip the camera 180* relative to target

function Quantum.Client.Cam.Stop() 
    hook.Remove( "CalcView", "Quantum_Cinematic" )
    Quantum.Client.Cam.Temp.scene_index = nil -- remove the var becuase it is unneeded
    Quantum.Debug( "Stopped cinematic." )
end

function Quantum.Client.Cam.Start( scene, loop )
    local frac = 0
    local time -- speed of the camera ( how long till it reaches its finish point )
    local fov 
    Quantum.Client.Cam.Temp = {}
    Quantum.Client.Cam.Temp.scene_index = 1

    local view = {} -- calcview vector data

    hook.Remove( "CalcView", "Quantum_Cinematic" ) -- if a cinematic is already running; cancel it

    hook.Add( "CalcView", "Quantum_Cinematic", function( ply, pos, ang, fov ) 
        time = scene[Quantum.Client.Cam.Temp.scene_index].velocity || 5
        fov = scene[Quantum.Client.Cam.Temp.scene_index].fov || 20
        frac = math.Clamp( frac + FrameTime()/time, 0, 1 )
        if( frac <= 0 ) then return end

        scene[Quantum.Client.Cam.Temp.scene_index].pos2 = scene[Quantum.Client.Cam.Temp.scene_index].pos2 || scene[Quantum.Client.Cam.Temp.scene_index].pos1 -- if there is no finish pos then make it stay still at starting pos
        scene[Quantum.Client.Cam.Temp.scene_index].ang2 = scene[Quantum.Client.Cam.Temp.scene_index].ang2 || scene[Quantum.Client.Cam.Temp.scene_index].ang1

        view.origin = LerpVector( frac, scene[Quantum.Client.Cam.Temp.scene_index].pos1, scene[Quantum.Client.Cam.Temp.scene_index].pos2 )
        view.angles = LerpAngle( frac, scene[Quantum.Client.Cam.Temp.scene_index].ang1, scene[Quantum.Client.Cam.Temp.scene_index].ang2 )
        view.fov = fov
        view.drawviewer = true

        if( view.origin:IsEqualTol( scene[Quantum.Client.Cam.Temp.scene_index].pos2, 1 ) ) then
            if( Quantum.Client.Cam.Temp.scene_index + 1 <= #scene ) then
                frac = 0
                Quantum.Client.Cam.Temp.scene_index = Quantum.Client.Cam.Temp.scene_index + 1
            end
            if( Quantum.Client.Cam.Temp.scene_index > #scene ) then -- if all scenes are finished, loop them if loop is enabled
                Quantum.Client.Cam.Temp.scene_index = 1 
            end 
            -- otherwise it will just stop at the end.
        end

        return view
    end)
end