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3D Computer Rendering
Kevin GintyCentre for Internet Technologies
www.cit.sunderland.ac.uk
Welcome!
Overview
The Sunderland Grid architecture The rendering process Four rendering applications trialled Emerging themes and common issues Grid rendering demo
Grid Architecture
40 compute nodes (plus 2 head nodes) runs Linux and Windows 2003 Server each node has
8GB RAM, 2 dual core processors 2.66GHz 250 GB local scratch disk 3 x 1GB network cards
Grid Architecture
Entirely self contained network Cisco 6500 series router 10 high specification workstations VoIP switchgear
Scali grid management software (Linux) Windows 2003 Server Compute Cluster Edition
(incorporating Grid administration) Can run either system Different parts of the grid can run different operating
systems i.e. some nodes can be running Linux while the rest are in Windows 2k3 CCE
Uses of rendering
Rendering applications are used for generating graphics, animations and simulations for Cartoons and movies (e.g. Toy Story, Star
Trek) Industrial models TV advertisements Walk-through simulations for architect’s
designs
The rendering process
Begins with a 3D model, known as a “wireframe”
Surface colour and texture detail for the object
Background information (may be photographic)
Light source and direction Camera angle(s)
The rendering process
Algorithms are then used to model the motion of the object(s) against the background, frame by frame
Each frame is then completed by filling in the areas on the wireframe with the colour and texture data
Each frame can take a long time to render – from several seconds through to several minutes
Frames are assembled into a movie file, and saved at the appropriate resolution
The rendering process - interface
The rendering process – camera angles
The rendering process - wireframe
AVIs
Rendering Applications
Four rendering applications were considered, three commercial and one open source:- Autodesk 3DS Max Maxon Cinema 4D NewTek Lightwave Blender
Uses of rendering
Rendering applications are used for generating graphics, animations and simulations for Cartoons and movies (e.g. Toy Story, Star Trek) Industrial models TV advertisements Walk-through simulations for architect’s designs
Examples (run avi’s) Robot Apache Guildhall
Rendering Applications - comparison
Autodesk 3DS Max the most widely used Blender is an open source alternative All four accomplish essentially the same job Differences in performance, arising from
differences in modality and use of system resources
Rendering applications – common issues
In order to run on the grid, frame rendering operations need to be farmed out to the compute nodes, processing carried out there, and the results collated afterwards.
Rendering applications have therefore to Transfer data to the nodes Run processes, either locally installed on the node or executable
code copied across at run-time Transfer the data back to a central location to be collated
afterwards Scheduling work on the nodes
Needs to be handled efficiently Rendering applications like to use the high performance
graphics adaptors found in workstations (but not in servers!)
Rendering applications – data transfer
One node (or workstation) manages the operation Data can be copied to and from the node
Directly from the workstation (may make a bottleneck on the workstation due to disk access times, and processor time spent on handling the file copying across to lots of nodes)
From a third point on the network acting as a data store (e.g. Network Attached Storage) which is better because the controlling node or workstation is not tied up most of the time on data transfer
Using mapped drives or UNC paths (Uniform Naming Convention) where the operating system handles the accessing of remote logical drives.
Transferring the files using dedicated processes and the nodes’ ip connections
Rendering applications – data transfer
Operationally, the tidiest way to do it would be via dedicated processes, and ip connections, using NAS storage
In practice, few rendering applications support all of this
NewTek Lightwave uses UNC paths to copy the data files back to the control node – which gets into trouble with the 10 connection limit for mapped drives in Windows XP…
Scheduling tasks on the compute nodes Efficiency varies enormously
Some applications (3DS Max) schedule quite well, and make fairly good use of available resources
Others (Blender/YADRA) schedule on the next free node, and count along from the beginning each time, meaning that nodes later in the sequence don’t get used unless the render operation takes a long time (and the earlier nodes are busy for longer…)
Lightwave clicks along the list of nodes, scheduling the next one every 3s or so, regardless of how long the jobs take, or whether or not the previous nodes have completed their tasks already… so if a render takes 12 seconds, only four of the nodes will ever be in use.
Rendering applications – OS environments
Most rendering applications specify Windows XP, with some using Vista and occasionally servers
Desktop environments like XP are preferred by the applications because Desktop boxes have high performance graphics adaptors XP has the drivers Server OS tend not to support powerful graphics, and may not
have drivers for high performance graphics cards Server hardware is usually configured so as to provide maximum
support to the network adaptors and disks, and not the display drivers
But…
Rendering applications – OS environments
Copying large amounts of data over the network Managing large numbers of simultaneous connections
(mapped drives or otherwise)
… are much better handled by server operating systems, which are designed to do so
Rendering applications – OS environments, and GPUs
Microsoft are currently considering this problem, as a range of applications (not just rendering) are utilising the computer power of the high performance graphics adaptors now found in most workstations
Solutions:- MS build the drivers for the cards into Server 2008 ! Start making server hardware that handles high
performance graphics as well…
Questions
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