CS 4115 SPINNER White Paper William Beaver1 wmb2013 columbia edu Gaurav Khandpur gaurav k cs columbia edu Marc Eaddy eaddy cs columbia edu Sangho Shin ss2020 cs columbia edu September 23 2003 1 team leader Chapter 1 Introduction 1 1 Background SPINNER is a general motion control language designed to control SPIN a performance art installation Slowly revolving orange wheels are projected onto a hanging grid of translucent Plexiglas circles The wheels act individually and in groups joining forces and breaking away in an evolving dance of whole and parts synchrony and disorder In SPIN sounds are produced as if each disc were a phonograph record As each disc spins fast or slow backwards or forwards speeding up or slowing down its sound follows accordingly SPIN was created by sound designer and multimedia artist Ben Rubin and presented at the Bumbershoot Visual Arts Exhibition in Seattle Washington from August 26th to September 1st 2003 SPIN is built in the MAX MSP programming environment a graphical environment for music audio and multimedia The basic environment that includes MIDI control user interface and timing objects is called Max Built on top of Max are MSP a set of audio processing objects that do everything from interactive filter design to hard disk recording and Jitter a set of matrix data processing objects optimized for video and 3 D graphics To originally control and coordinate the movement of each of SPIN s six discs a simple asynchronous linear scripting language SPINscript was created This language is comprised of a number of initialization parameters and three simple primitive functions wait line and speed The initialization parameters setup audio gain assign sound samples to each disc etc and define the physics of the system for example disc acceleration and deceleration The primitives are used in concert to control and coordinate the motion of each disc Line tells a particular disc to rotate to a particular angle within a specific timeframe Speed changes the linear acceleration of a disc By using the wait command a programmer can set discs in motion and then wait a specific time period before issuing the next set of com 1 Figure 1 1 SPIN component diagram SPINNER program read by SPINNER compiler SPINNER compiler outputs SPINscript which is read by SPIN to control projection of discs 2 mands allowing the discs to move in space according to the direction of the line and speed commands SPINscript is asynchronous Without the wait command a script attempting to coordinate disc movement by issuing a series of specific motions would in actuality set a disc into one motion which is exactly the additive result of all the commands issued in the script for a disc SPINNER is a new language for SPIN SPINNER is intended to replace SPINscript as the primary interface for expressiveness in SPIN and to solve many of the problems that are inherent in the existing language see below SPINNER will generate a file that is compatible with the existing SPINscript language and is subsequently used to control SPIN 1 2 The Problem The original SPINscript language has a number of deficiencies that inevitably limit the expressiveness of individual disc motion and the potential complexity of disc interaction 1 2 1 Primitive programming model SPINscript has a strictly sequential control flow It does not support looping function calls or jumps If the user wants to gradually increase the speed of a disc or play the same sequence several times they have to laboriously duplicate the scripting code by hand Another problem is that SPINscript does not support variables or constants This leads to a proliferation of magic numbers throughout the script whose intent is impossible to discern If the artist wants to increase the speed of an entire sequence by a factor of two she has to calculate and modify each number by hand This is one area which makes the language very brittle 1 2 2 Syntax is non intuitive SPINscript lines follow the following format number disc cmd args number wait ms number comment Here are some examples 1 6 speed 50 10000 1 wait 14000 1 straight up now 3 There are several problems with this syntax 1 The first value 1 is unnecessary The script language designer has indicated that the number portion isn t used 2 The disc number that a command operates on is prefixed to the command s name eg 6 speed This syntax is limiting it does not allow actions on multiple discs and it is unintuitive 3 Arguments to functions are not bound to the function name 4 The wait command does not have the same syntax as other SPINscript commands It almost looks like a comment 5 Comments implicitly indicated by the lack of a keyword after rather than explicitly stated through their own syntax 1 2 3 Modeling limitations SPINscript models changing the angles of six independent discs over time However this only models part of what the artist is trying to achieve In many of the scenes the artist requires that the behavior of the discs be dependent on each other For example a scene might start out with all discs rotating at different speeds This goes on for several seconds Then when two discs happen to both be at 0 degrees rotation the artist wants both discs to synchronize their rotation speed Unfortunately SPINscript does not have a built in mechanism to perform this synchronization The artist has to do this calculation manually which is tedious and prone to error Because of the manual labor involved scripts must be kept small and simple This ultimately limits the artist s expressiveness 1 3 1 3 1 Our Goals Improved programming model We will support various methods for control flow loops iteration non recursive function calls We will support integer and floating point variables Additionally SPINNER provides some built in functions and operations and the ability to define new functions and procedures using these primitives For example we are considering supporting sine cosine and tangent 4 functions in addition to the basic math operations of addition subtraction multiplication and division Here is an example1 Start all the discs spinning at different speeds based on sine function for i 1 to 6 revolve i 1 sine i 1000 In addition to the for loop function call and variable use this example also shows how the disc number will become an argument to the function instead of being part of the function name 1 3 2 Intuitive language syntax The programmer must be able to transform concepts of the motion of images in space
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