seminar ii rendering architectures · for its own segment of image. • load imbalance problem in...
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Seminar IIRendering Architectures
Radek CirmirakisJaume Mateu24th of October 2007
Contents
• Consumer graphic cards• The rendering pipeline
– geometric transformation– Rasterization
• Graphics subsystems• Parallelization of rendering pipeline• Parallel and cluster architecture• Questions?
Contents
• Consumer graphic cards• The rendering pipeline
– geometric transformation– Rasterization
• Graphics subsystems• Parallelization of rendering pipeline• Parallel and cluster architecture• Questions?
Overview of the capabilities of consumer cards
11.9 Gigapixel/s
14.7 Gigapixel/s
Peak pixel fill rate (theoretical)
Photo
Radeon HD 2900 XT (ATI)
GeForce 8800 Ultra (Nvidia)Graphical Card
Contents
• Consumer graphic cards• The rendering pipeline
– geometric transformation– Rasterization
• Graphics subsystems• Parallelization of rendering pipeline• Parallel and cluster architecture• Questions?
The graphic pipeline • The Graphic Pipeline
mechanism transforms 3D Computer Graphics stored as data in a computer into pixels values in one or more screens. It is divided into two stages.
Contents
• Consumer graphic cards• The rendering pipeline
– geometric transformation– Rasterization
• Graphics subsystems• Parallelization of rendering pipeline• Parallel and cluster architecture• Questions?
The rendering pipeline
• Geometric transformationTransforms 3D maps (triangles) to the 2D coordinate system
• RasterizationTransforms triangles into pixel values on the screen
Geometric transformation
• Modellingtransformation positions primitives with respect to each other. The viewing transformation orients the resulting set of primitives to the user viewpoint
COPView Window (showing pixels)
Geometric transformation
• This stage evaluates the colour of the vertices given the direction of light, the vertex position, and the surface-normal vector and material characteristics of an object’s surface
Geometric transformation
• This transformation projects objects onto the screen.
Projection transform
• Orthographic projection:Keeps the original size of 3D objects and hence is useful for architectural and computer-aided design
• Perspective projection:Creates more realistic images by making distant objects appear smaller
Geometric transformation
• Removes the objects that are outside the viewable area
Geometric transformation
• Convert homogeneous coordinates to Cartesian coordinates
Geometric transformation
• This step performs the final scaling and translation to map the vertices from the projected coordinate system to the actual viewport on the computer screen
Resterization
• Convert triangles after geometric transformations into set of pixels with assigned attributes
Resterization
• Pixel processing – apply texture elements to pixels
Resterization
• Pixel processing – investigate pixel visibility (remove “covered” pixels)
Resterization
• Pixel processing – colour of old and new pixels is mixed using α value
Contents
• Consumer graphic cards• The rendering pipeline
– geometric transformation– Rasterization
• Graphics subsystems• Parallelization of rendering pipeline• Parallel and cluster architecture• Questions?
PCI-Express graphics subsystem
PCI slot • The Peripheral
Component Interconnect, or PCI Standard (in practice almost always shortened to PCI), specifies a computer bus for attaching peripheral devices to a computer motherboard.
PCI slot
• 33.33 MHz clock with synchronous transfers• peak transfer rate of 133 MB per second for 32-
bit bus width (33.33 MHz × 32 bits ÷ 8 bits/byte = 133 MB/s)
• peak transfer rate of 266 MB/s for 64-bit bus width * 32-bit or 64-bit bus width
• 32-bit address space (4 gigabytes)• 32-bit I/O port space (now deprecated)• 256-byte configuration space• 5-volt signaling * reflected-wave switching
AGP slot• It's main advantage over PCI is that
provides a dedicated pathway between the slot and the processor
PCI - Express
• It's better than AGP because is full duplex instead of half duplex
• 4GB/s per direction
Speed up GPU efficiency
• Many pipelines of graphical tasks• Many GPUs located in many computers
working together as one machine• Multiple computers, PC-custers
Contents
• Consumer graphic cards• The rendering pipeline
– geometric transformation– Rasterization
• Graphics subsystems• Parallelization of rendering pipeline• Parallel and cluster architecture• Questions?
Parallel architecture overview
• Multiple GPUs– Low latency bus– Renders on a close-proximity– Are used more frequently in consumers PC
NVIDA GeForce 8800ATI Radeon 2900 XT
Parallelism
• Design a single component and replicate it to increase performance
• Create pipelining (tasks overlapping)• Connects components giving opportunity to work
parallel.• Reduce the total polygon rendering time.
• There are same tasks that cannot be paralyzed
Parallel rendering
• Alternate frame rendering
• Sort-first• Sort-middle• Sort-last
Sort-first• Each processor is assigned to a
portion of screen to render• Each node performs geometry
transformation and rasterizationfor its own segment of image.
• Load imbalance problem in transformation and resterizationstage
• Low network usage
Sort-middle• Each processor is assigned to a
portion of screen to render• Geometry transformation is
performed by master node• Resterization by slave nodes • Less Load imbalance problem
in transformation and resterization stage
Sort-last• Arbitrary division of the scene• Each node executes full
rendering pipeline on its scene section
• No Load imbalance problems• High-bandwidth network
required
Contents
• Consumer graphic cards• The rendering pipeline
– geometric transformation– Rasterization
• Graphics subsystems• Parallelization of rendering pipeline• Parallel and cluster architecture• Questions?
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