OpenGL ARB Superbuffers

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OpenGL ARB Superbuffers

• Rob Mace
• mace_at_ati.com

2
First Some History

• When OpenGL 1.0 was created
• Framebuffer resources were static.
• Memory for framebuffers, textures, and vertex
  arrays (actually not in 1.0) were all separate
  physical memories.
• In OpenGL 1.0 the framebuffer was made a window
  system resource, on loan to OpenGL.

3
Graphics Hardware Has Evolved

• Framebuffer resources are now generally dynamic.
• The memory used by framebuffers, textures, and
  vertex arrays is now often in a shared set of
  physical memories.

4
Evolving OpenGL

• Add memory objects that can be used as the memory
  of framebuffers, textures, and vertex arrays.
• Add framebuffer objects that are GL allocated and
  managed resources.

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What Functionality Does This Add To OpenGL?

• A light weight method to change which framebuffer
  is being rendered to.
• Render to texture.
• Render to vertex array.
• Combined with programmable shaders and floating
  point memories the possibilities are endless.

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Uber Buffers Extensions

• ARB_uber_buffers
• ARB_uber_vertex_array
• ARB_uber_mem_image
• ARB_swap_buffers

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ARB_uber_buffers

• Adds memory objects.
• Adds framebuffer objects.
• DRAW_FRAMEBUFFER binding point.
• READ_FRAMEBUFFER binding point.
• Memory objects attachable to textures and
  framebuffers.

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ARB_uber_vertex_array

• Depends on ARB_uber_buffers.
• Memory objects attachable to vertex arrays.

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ARB_mem_image

• Depends on ARB_uber_buffers.
• Adds glMemImage and glGetMemImage commands.

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ARB_swap_buffers

• Interacts with ARB_uber_buffers, but not
  dependent on it.
• Adds glSwapBuffers.
• Adds SWAP_SRC_FRAMEBUFFER and SWAP_DST_FRAMEBUFFER
  binding points.

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Memory Objects

• Structured Memory
• Has defined dimensions.
• Has defined format.
• Attachable as the memory of
• Textures Objects
• Framebuffers Objects
• Vertex Arrays

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Creating Memory Objects

• GLmemARB glAllocMem1DARB(GLenum format, GLsizei
  width,
• GLsizei np,
• const GLint
  properties)
• GLmemARB glAllocMem2DARB(GLenum format, GLsizei
  width,
• GLsizei height, GLsizei
  np,
• const GLint
  properties)
• GLmemARB glAllocMem3DARB(GLenum format, GLsizei
  width,
• GLsizei height, GLsizei
  depth,
• GLsizei np,
• const GLint properties)

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Creating Memory Objects (cont.)

• AllocMem returns a valid memory object handle on
  success.
• AllocMem returns 0 on failure.
• format is the internal format of the memory
  object. Uses the same internal format enumerants
  as glTexImage.
• GL_RGBA8, etc.

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Memory Object Properties

• The properties argument of AllocMem is an array
  of property/value pairs.
• Properties define what the memory object is, and
  how it can be used.

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Properties Array Example

• GLint properties GL_MIPMAP_ARB,
  GL_TRUE,
• GL_TEXTURE_2D,
  GL_TRUE,
• GL_COLOR_BUFFER_ARB,
  GL_TRUE
• GLmemARB mem
• mem glAllocMem2DARB(GL_RGBA8, 256, 256, 3,
  properties)

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Property Types

• Structure Properties
• Capability Properties
• Allocation Properties
• Configuration Properties
• Automatic Properties (Not Settable)

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Structure Properties

• GL_MIPMAP_ARB
• GL_CUBE_MAP_ARB
• GL_DEPTH_SLICED_ARB

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Capability Properties

• GL_COLOR_BUFFER_ARB
• GL_DEPTH_BUFFER_ARB
• GL_STENCIL_BUFFER_ARB
• GL_ACCUMULATION_BUFFER_ARB

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Capability Properties (cont.)

• GL_TEXTURE_1D
• GL_TEXTURE_2D
• GL_TEXTURE_3D
• GL_TEXTURE_CUBE_MAP
• GL_TEXTURE_RECTANGLE_EXT
• GL_VERTEX_ARRAY

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Configuration Properties

• GL_SAMPLES
• GL_BORDER_ARB
• GL_ACCESS_PATTERN_ARB
• GL_PROXY_ARB

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Allocation Properties

• GL_MATCH_SIZE_ARB
• GL_MATCH_COMPONENT_SET_ARB
• GL_MATCH_COMPONENT_SIZE_ARB
• GL_MATCH_COMPONENT_TYPE_ARB
• GL_MATCH_SAMPLES_ARB
• GL_VALIDATE_ONLY_ARB

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Automatic Properties

• GL_MEMORY_DIMENSIONS_ARB
• GL_MEMORY_WIDTH_ARB
• GL_MEMORY_HEIGHT_ARB
• GL_MEMORY_DEPTH_ARB
• GL_MEMORY_LEVELS_ARB

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Automatic Properties (cont.)

• GL_BASE_FORMAT_ARB
• GL_RED_BITS
• GL_GREEN_BITS
• Etc.
• GL_RED_TYPE_ARB
• GL_GREEN_TYPE_ARB
• Etc.

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Automatic Properties (cont.)

• GL_IS_BASE_MEM_ARB
• GL_WINDOW_SYSTEM_ALLOCATED_ARB
• GL_FLAGGED_FOR_DELETION_ARB

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Cloning Memory Objects

• Memory objects can be cloned.
• Cloning does not copy contents.
• GLmemARB glCloneMemARB(GLmemARB mem)

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Proxy Memory Objects

• Created with GL_PROXY_ARB property set to
  GL_TRUE.
• Have no storage.
• Clones of proxy memory objects are real memory
  objects and have storage.

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Memory Object Structure

• The structure properties define the structure of
  a memory object.
• Memory object structure is exposed as a set of
  sub memory objects.

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Mipmap Structure
Base Memory Object
Mipmap Level Sub Memory Objects
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Sub Memory Objects

• Sub memory objects are named selectors that
  select a sub portion of a memory objects memory.
• Sub memory objects are indivisible from their
  base memory object.

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Getting Sub Memory Objects

• GLmemARB glGetSubMemARB(GLmemARB mem,
• GLenum type,
• GLuint sub)
• type is one of
• GL_MIPMAP_ARB
• GL_CUBE_MAP_ARB
• GL_DEPTH_SLICED_ARB
• sub is type specific.

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Deleting Memory Objects

• GLvoid glDeleteMemARB(GLmemARB mem)
• If a memory objects is not currently attached, it
  is deleted.
• If it is currently attached, it is flagged for
  deletion.
• Sub memory objects cannot be deleted. Delete the
  base memory object instead.

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Attaching Memory Objects To Texture Objects

• GLvoid glAttachTextureMemARB(GLuint texture,
• GLenum attachment,
• GLmemARB mem)
• texture is a texture object id.
• attachment must be GL_IMAGES_ARB.
• mem is the memory object to attach.
• mem of 0 will detach any attached memory object.

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Texture Attachment Example

• GLint properties GL_MIPMAP_ARB,
  GL_TRUE,
• GL_TEXTURE_2D,
  GL_TRUE,
• GL_COLOR_BUFFER_ARB,
  GL_TRUE
• GLmemARB mem
• GLuint tex
• mem glAllocMem2DARB(GL_RGBA8, 256, 256, 3,
  properties)
• glGenTextures(1, tex)
• glAttachTextureMemARB(tex, GL_IMAGES_ARB, mem)

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Texture Attachment Notes

• glTexImage commands work but dimensions and
  internalFormat must match.
• glTexSubImage commands work.
• GL_GENERATE_MIPMAP parameter has no effect.
  Instead use
• GLvoid glMemGenerateMipmapARB(GLmemARB mem,
• GLuint base)

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Creating Framebuffer Objects

• GLuint glCreateFramebufferARB(GLvoid)
• Framebuffer objects have no buffers when created.
• Memory objects are attached to buffer attachment
  points in a framebuffer object.

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Attaching Memory Objects To Framebuffer Objects

• GLvoid glAttachFramebufferMemARB(GLuint
  framebuffer,
• GLenum
  attachment,
• GLmemARB mem)
• framebuffer is a framebuffer object id.
• attachment is the buffer to attach mem as.
• mem is the memory object to attach.
• mem of 0 will detach any memory object attached
  to attachment.

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Framebuffer Attachment Points

• GL_FRONT_LEFT or GL_FRONT
• GL_FRONT_RIGHT
• GL_BACK_LEFT or GL_BACK
• GL_BACK_RIGHT
• GL_AUX0, GL_AUX1, etc.
• GL_DEPTH_BUFFER_ARB
• GL_STENCIL_BUFFER_ARB

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Framebuffer Attachment Points (cont.)

• GL_COLOR_SAMPLES_ARB
• GL_DEPTH_SAMPLES_ARB
• GL_STENCIL_SAMPLES_ARB
• GL_ACCUMULATION_BUFFER_ARB

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Framebuffer Attachment Example

• GLint properties GL_MIPMAP_ARB,
  GL_TRUE,
• GL_TEXTURE_2D,
  GL_TRUE,
• GL_COLOR_BUFFER_ARB,
  GL_TRUE
• GLmemARB mem
• GLuint fb
• mem glAllocMem2DARB(GL_RGBA8, 256, 256, 3,
  properties)
• fb glCreateFramebufferARB()
• glAttachFramebufferMemARB(fb, GL_BACK, mem)

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Binding Framebuffer Objects

• GLvoid glBindFramebufferARB(GLenum target,
• uint framebuffer),
• target can be
• GL_DRAW_FRAMEBUFFER
• GL_READ_FRAMEBUFFER
• framebuffer is a framebuffer object id.
• framebuffer of 0 binds the original window system
  framebuffer object.

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Render to Texture Example

• GLint color_props GL_MIPMAP_ARB,
  GL_TRUE,
• GL_TEXTURE_2D,
  GL_TRUE,
• GL_COLOR_BUFFER_ARB,
  GL_TRUE
• GLint depth_props GL_DEPTH_BUFFER_ARB,
  GL_TRUE
• GLmemARB color_mem, level_mem, depth_mem
• GLuint fb
• GLuint tex

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Render to Texture Example(cont.)

• /
• Create objects
• /
• color_mem glAllocMem2DARB(GL_RGBA8,
• 256, 256, 3,
  color_props)
• depth_mem glAllocMem2DARB(GL_DEPTH_COMPONENT24,
• 256, 256, 1,
  depth_props)
• level_mem glGetSubMemARB(color_mem,
  GL_MIPMAP_ARB, 0)
• fb glCreateFramebufferARB()
• glGenTextures(1, tex)

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Render to Texture Example(cont.)

• /
• Make attachments
• /
• glAttachFramebufferMemARB(fb, GL_BACK,
  level_mem)
• glAttachFramebufferMemARB(fb, GL_DEPTH_BUFFER_ARB,
  
• depth_mem)
• glAttachTextureMemARB(tex, GL_IMAGES_ARB,
  color_mem)

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Render to Texture Example(cont.)

• glBindFramebufferARB(GL_DRAW_FRAMEBUFFER_ARB,
  fb)
• glDrawBuffer(GL_BACK)
• ltrender to the texturegt
• glBindFramebufferARB(GL_DRAW_FRAMEBUFFER_ARB, 0)
• glMemGenerateMipmapARB(color_mem, 0)
• glBindTexture(GL_TEXTURE_2D, tex)
• ltrender using the texturegt

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Attaching Memory Objects As Vertex Arrays

• GLvoid glAttachVertexArrayMemARB(GLuint arraySet,
• GLenum array,
• GLint size,
• GLmemARB mem,
• GLuint offset)
• arraySet must be 0.
• array is the array to attach mem as.
• size specifies the number of components to use.
• mem is the memory object to attach.
• offset is the element offset into the mem.

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Vertex Array Attachment

• Element indexing of 1D memory objects is
• i x
• Element indexing of 2D memory objects is
• i y width x

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Rendering To Vertex Arrays

• Recommended that GL_MATCH_SIZE property be set to
  GL_MIN or GL_MIN_ELEMENTS_ARB when allocating
  renderable vertex array memory objects.
• When rendering, draw a small number of
  primitives that touch each vertex to be rendered
  once.

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Render to Vertex Array Example

• GLint properties GL_MATCH_SIZE_ARB,
  GL_MIN_ELEMENTS_ARB,
• GL_VERTEX_ARRAY,
  GL_TRUE,
• GL_COLOR_BUFFER_ARB,
  GL_TRUE
• GLmemARB mem
• GLint width, height
• GLuint fb
• /
• Create objects
• /
• mem glAllocMem2DARB(GL_RGBA32F_ARB, 10000, 1,
  3, properties)
• width glGetMemPropertyARB(mem,
  GL_MEMORY_WIDTH_ARB)
• height glGetMemPropertyARB(mem,
  GL_MEMORY_HEIGHT_ARB)
• fb glCreateFramebufferARB()

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Render to Vertex Array Example (cont.)

• glAttachFramebufferMemARB(fb, GL_BACK, mem)
• glBindFramebufferARB(GL_DRAW_FRAMEBUFFER_ARB,
  fb)
• glDrawBuffer(GL_BACK)
• ltrender to the vertex arraygt
• glBindFramebufferARB(GL_DRAW_FRAMEBUFFER_ARB, 0)
• glAttachVertexArrayMemARB(0, 3,
  GL_VERTEX_ARRAY_ARB,
• mem, 0)
• ltrender using the vertex arraygt

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ARB_SWAP_BUFFERS

• Adds swap framebuffer binding points
• GL_SWAP_SRC_FRAMEBUFFER_ARB
• GL_SWAP_DST_FRAMEBUFFER_ARB
• Adds
• GLvoid glSwapBuffersARB(GLvoid)
• Swaps from the back buffer of the swap src
  framebuffer to the front buffer of the swap dst
  framebuffer.

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ARB_SWAP_BUFFERS (cont.)

• Adds framebuffer parameters
• GL_SWAP_PRESERVE_ARB
• Preserve back buffer contents on swap.
• GL_SWAP_SYNC_ARB
• Synchronize swaps to display.
• GL_SWAP_INTERVAL_ARB
• Interval of swaps when synchronized.

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This Is Not Final

• The OpenGL ARB superbuffers working groups is
  still working to complete these extensions and
  get final agreement on them.

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Demos

• Particle system demos by
• Dr. Peter Kipfer
• Computer Graphics Visualization Group, TU
  Munich
• All particle computations in these demos done
  using GPU. Including
• Motion
• Collisions
• Color
• Sorting

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Thanks To

• The members of the OpenGL ARB superbuffers
  working group.
• Dr. Peter Kipfer (demos)

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Questions?