Chapter 2. The Graphics Rendering Pipeline ???????

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Chapter 2. The Graphics Rendering
Pipeline???????
??? Email jin_at_cad.zju.edu.cn ????CADCG???????,
?I ??
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????

• ?????????????????????????????????????????????
• A chain is no stronger than its weakest
  link?????????????(bottleneck)??????????
• ???????????(function)??????(implementation)?

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Architecture(????)
Three conceptual stages
Application
Rasterizer
Geometry
Each stage may be a pipeline
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Application Stage(???)CPU

• ??????,???????(????????????)
• ???????Rendering primitives(????????)
• Processes??????????????????Morphing???????(??????
  VR??)????

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The Geometry Stage(???)

• ???????????????

Model view Transform
Lighting
Projection
Clipping
Screen Mapping
???????????????
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Model and View Transform
Model space
World space
Model transform
Model coordinates
World coordinates
Camera or eye space
View transform
Camera coordinates
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Lighting and Shading

• ????????????????(??????????????)
• ??????????(?????????)
• ??????????Gouraud shading

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Projection

• ??????????????,????(view volume)?????????
• ??????????(orthographic or parallel
  projection)?????(perspective projection)
• ??????????????????????????????????
• ?????????????????????????????,?????????,?????????

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Clipping

• ?????????????????????
• ??????????????????????????????
• ???????????,?????????????,?????????

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???
?????
x
x
Clipping
z
z
???
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Screen Mapping
?????
(x2,y2)
Screen mapping
Test OOO
(x1,y1)
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The Rasterizer Stage(????)

• ????????????
• ??Per-pixel operations
• ?????????????(color buffer)
• ???buffer?????back buffer??,??????,????front
  buffer
• ?????????? ?????????Z-buffer??
• Z-buffer????????????Z?

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Z-buffer ??

• ???????Z??Z-buffer??????,????Z?????????
• ???????Z??Z-buffer??????,????Z??????
• ????????????????????????????O(n)??????????

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??????buffer

• Color buffer ????????
• Z buffer?????Z?
• Alpha buffer ?????????
• Stencil buffer(?????) ?????????????OpenGL????,?
  ???????18 Bits???????????????????,????????????Col
  or buffer?Z buffer??????????????????????,???????
  ???????????,?????????

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??????buffer(?)

• Frame buffer????????buffer,?????Color buffer?Z
  buffer
• Accumulation buffer(????) 1990?Haeberli?Akeley???
  ?????,????????????????????????(motion
  blur)??????????(depth of field)???

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? ?
GPU
CPU
Application
Rasterizer
Geometry
????

• ?????????????,?????????,????????????????????????
• ???????????!??????,?????!

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Graphics Pipeline GPU
GPU
CPU
Graphics State
VertexProcessor
PixelProcessor
Application
VertexProcessor
Assembly Rasterization
PixelProcessor
VideoMemory(Textures)
Vertices(3D)
Xformed,LitVertices(2D)
Fragments(pre-pixels)
Finalpixels(Color, Depth)
Render-to-texture

• Note
• Vertex processor does all transform and lighting
• Pipe widths vary
• Intra-GPU pipes wider than CPU?GPU pipe
• Thin GPU?CPU pipe
• Many caches and FIFOs not shown
• Soon render-to-vertex-array

• Heres whats cool
• Can now program vertex processor!
• Can now program pixel processor!

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Graphics Pipeline GPU
Framebuffer
Fragment Processor
Rasterizer
Geometry Processor
Geometry Storage
CPU
Texture Storage Filtering
Vertices
Pixels
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Possible Bottlenecks
CPU
transfer
transform
raster
texture
fragment
frame buffer
Framebuffer
Fragment Processor
Rasterizer
Geometry Processor
Geometry Storage
CPU
Texture Storage Filtering
CPU/Bus Bound
Vertex Bound
Pixel Bound