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364 строки
15 KiB
Plaintext
Name
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ANGLE_framebuffer_multisample
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Name Strings
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GL_ANGLE_framebuffer_multisample
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Contributors
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Contributors to EXT_framebuffer_multisample
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Daniel Koch, TransGaming Inc.
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Shannon Woods, TransGaming Inc.
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Kenneth Russell, Google Inc.
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Vangelis Kokkevis, Google Inc.
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Contacts
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Daniel Koch, TransGaming Inc. (daniel 'at' transgaming 'dot' com)
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Status
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Implemented in ANGLE ES2
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Version
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Last Modified Date: Aug 6, 2010
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Author Revision: #3
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Number
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OpenGL ES Extension #84
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Dependencies
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Requires OpenGL ES 2.0.
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Requires GL_ANGLE_framebuffer_blit (or equivalent functionality).
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The extension is written against the OpenGL ES 2.0 specification.
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OES_texture_3D affects the definition of this extension.
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Overview
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This extension extends the framebuffer object framework to
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enable multisample rendering.
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The new operation RenderbufferStorageMultisampleANGLE() allocates
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storage for a renderbuffer object that can be used as a multisample
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buffer. A multisample render buffer image differs from a
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single-sample render buffer image in that a multisample image has a
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number of SAMPLES that is greater than zero. No method is provided
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for creating multisample texture images.
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All of the framebuffer-attachable images attached to a framebuffer
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object must have the same number of SAMPLES or else the framebuffer
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object is not "framebuffer complete". If a framebuffer object with
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multisample attachments is "framebuffer complete", then the
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framebuffer object behaves as if SAMPLE_BUFFERS is one.
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The resolve operation is affected by calling
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BlitFramebufferANGLE (provided by the ANGLE_framebuffer_blit
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extension) where the source is a multisample application-created
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framebuffer object and the destination is a single-sample
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framebuffer object (either application-created or window-system
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provided).
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New Procedures and Functions
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void RenderbufferStorageMultisampleANGLE(
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enum target, sizei samples,
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enum internalformat,
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sizei width, sizei height);
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New Types
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None.
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New Tokens
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Accepted by the <pname> parameter of GetRenderbufferParameteriv:
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RENDERBUFFER_SAMPLES_ANGLE 0x8CAB
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Returned by CheckFramebufferStatus:
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FRAMEBUFFER_INCOMPLETE_MULTISAMPLE_ANGLE 0x8D56
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Accepted by the <pname> parameter of GetBooleanv, GetIntegerv,
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and GetFloatv:
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MAX_SAMPLES_ANGLE 0x8D57
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Additions to Chapter 2 of the OpenGL ES 2.0 Specification (OpenGL Operation)
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Additions to Chapter 3 of the OpenGL ES 2.0 Specification (Rasterization)
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Add to the last paragraph of 3.7.2 (Alternate Texture Image Specification)
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(as modified by ANGLE_framebuffer_blit) the following:
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"Calling CopyTexSubImage3DOES, CopyTexImage2D or CopyTexSubImage2D will
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result in INVALID_OPERATION being generated if the object bound to
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READ_FRAMEBUFFER_BINDING_ANGLE is "framebuffer complete" and the value
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of SAMPLE_BUFFERS is greater than zero."
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Additions to Chapter 4 of the OpenGL ES 2.0 Specification (Per-Fragment
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Operations and the Framebuffer)
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Add to 4.3.1 (Reading Pixels), right before the subsection titled
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"Obtaining Pixels from the Framebuffer":
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"ReadPixels generates INVALID_OPERATION if READ_FRAMEBUFFER_BINDING_ANGLE
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(section 4.4) is non-zero, the read framebuffer is framebuffer
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complete, and the value of SAMPLE_BUFFERS for the read framebuffer
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is greater than zero."
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In 4.3.2 (Copying Pixels), add to the section describing BlitFramebuffer
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that was added by ANGLE_framebuffer_blit.
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"If SAMPLE_BUFFERS for the read framebuffer is greater than zero and
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SAMPLE_BUFFERS for the draw framebuffer is zero, the samples
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corresponding to each pixel location in the source are converted to
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a single sample before being written to the destination.
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If SAMPLE_BUFFERS for the draw framebuffer is greater than zero,
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no copy is performed and an INVALID_OPERATION error is generated.
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If SAMPLE_BUFFERS for the read framebuffer is greater than zero and
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<mask> includes DEPTH_BUFFER_BIT or STENCIL_BUFFER_BIT, no copy is
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performed and an INVALID_OPERATION error is generated.
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If SAMPLE_BUFFERS for the read framebuffer is greater than zero and
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the format of the read and draw framebuffers are not identical, no
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copy is performed and an INVALID_OPERATION error is generated.
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If SAMPLE_BUFFERS for the read framebuffer is greater than zero, the
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dimensions of the source and destination rectangles provided to
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BlitFramebufferANGLE must be identical and must specify the complete
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source and destination buffers, otherwise no copy is performed and
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an INVALID_OPERATION error is generated."
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Modification to 4.4.3 (Renderbuffer Objects)
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Add, just above the definition of RenderbufferStorage:
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"The command
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void RenderbufferStorageMultisampleANGLE(
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enum target, sizei samples,
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enum internalformat,
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sizei width, sizei height);
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establishes the data storage, format, dimensions, and number of
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samples of a renderbuffer object's image. <target> must be
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RENDERBUFFER. <internalformat> must be one of the color-renderable,
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depth-renderable, or stencil-renderable formats described in table 4.5.
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<width> and <height> are the dimensions in pixels of the renderbuffer. If
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either <width> or <height> is greater than the value of
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MAX_RENDERBUFFER_SIZE, or if <samples> is greater than MAX_SAMPLES_ANGLE,
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then the error INVALID_VALUE is generated. If OpenGL ES is unable to
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create a data store of the requested size, the error OUT_OF_MEMORY
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is generated.
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Upon success, RenderbufferStorageMultisampleANGLE deletes any existing
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data store for the renderbuffer image and the contents of the data
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store after calling RenderbufferStorageMultisampleANGLE are undefined.
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RENDERBUFFER_WIDTH is set to <width>, RENDERBUFFER_HEIGHT is
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set to <height>, and RENDERBUFFER_INTERNAL_FORMAT is set to
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<internalformat>.
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If <samples> is zero, then RENDERBUFFER_SAMPLES_ANGLE is set to zero.
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Otherwise <samples> represents a request for a desired minimum
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number of samples. Since different implementations may support
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different sample counts for multisampled rendering, the actual
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number of samples allocated for the renderbuffer image is
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implementation dependent. However, the resulting value for
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RENDERBUFFER_SAMPLES_ANGLE is guaranteed to be greater than or equal
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to <samples> and no more than the next larger sample count supported
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by the implementation.
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An OpenGL ES implementation may vary its allocation of internal component
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resolution based on any RenderbufferStorageMultisampleANGLE parameter (except
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target), but the allocation and chosen internal format must not be a
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function of any other state and cannot be changed once they are
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established. The actual resolution in bits of each component of the
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allocated image can be queried with GetRenderbufferParameteriv."
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Modify the definiton of RenderbufferStorage as follows:
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"The command
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void RenderbufferStorage(enum target, enum internalformat,
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sizei width, sizei height);
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is equivalent to calling RenderbufferStorageMultisampleANGLE with
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<samples> equal to zero."
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In section 4.4.5 (Framebuffer Completeness) in the subsection
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titled "Framebuffer Completeness" add an entry to the bullet list:
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* The value of RENDERBUFFER_SAMPLES_ANGLE is the same for all attached
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images.
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{ FRAMEBUFFER_INCOMPLETE_MULTISAMPLE_ANGLE }
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Also add a paragraph to the end of the section after the definition
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of CheckFramebufferStatus:
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"The values of SAMPLE_BUFFERS and SAMPLES are derived from the
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attachments of the currently bound framebuffer object. If the
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current DRAW_FRAMEBUFFER_BINDING_ANGLE is not "framebuffer complete",
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then both SAMPLE_BUFFERS and SAMPLES are undefined. Otherwise,
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SAMPLES is equal to the value of RENDERBUFFER_SAMPLES_ANGLE for the
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attached images (which all must have the same value for
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RENDERBUFFER_SAMPLES_ANGLE). Further, SAMPLE_BUFFERS is one if
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SAMPLES is non-zero. Otherwise, SAMPLE_BUFFERS is zero.
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Additions to Chapter 5 of the OpenGL ES 2.0 Specification (Special Functions)
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Additions to Chapter 6 of the OpenGL ES 2.0 Specification (State and State
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Requests)
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In section 6.1.3 (Enumeraged Queries), modify the third paragraph
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of the description of GetRenderbufferParameteriv as follows:
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"Upon successful return from GetRenderbufferParameteriv, if
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<pname> is RENDERBUFFER_WIDTH, RENDERBUFFER_HEIGHT,
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RENDERBUFFER_INTERNAL_FORMAT, or RENDERBUFFER_SAMPLES_ANGLE, then <params>
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will contain the width in pixels, height in pixels, internal format, or
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number of samples, respectively, of the image of the renderbuffer
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currently bound to <target>."
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Dependencies on ANGLE_framebuffer_blit
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ANGLE_framebuffer_blit is required. Technically, ANGLE_framebuffer_blit
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would not be required to support multisampled rendering, except for
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the fact that it provides the only method of doing a multisample
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resovle from a multisample renderbuffer.
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Dependencies on OES_texture_3D
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On an OpenGL ES implementation, in the absense of OES_texture_3D,
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omit references to CopyTexSubImage3DOES.
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Errors
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The error INVALID_OPERATION is generated if ReadPixels or
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CopyTex{Sub}Image* is called while READ_FRAMEBUFFER_BINDING_ANGLE
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is non-zero, the read framebuffer is framebuffer complete, and the
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value of SAMPLE_BUFFERS for the read framebuffer is greater than
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zero.
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If both the draw and read framebuffers are framebuffer complete and
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the draw framebuffer has a value of SAMPLE_BUFFERS that is greater
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than zero, then the error INVALID_OPERATION is generated if
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BlitFramebufferANGLE is called.
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If both the draw and read framebuffers are framebuffer complete and
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the read framebuffer has a value of SAMPLE_BUFFERS that is greater
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than zero, the error INVALID_OPERATION is generated if
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BlitFramebufferANGLE is called and any of the following conditions
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are true:
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- <mask> includes DEPTH_BUFFER_BIT or STENCIL_BUFFER_BIT.
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- the source or destination rectangles do not specify the entire
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source or destination buffer.
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If both the draw and read framebuffers are framebuffer complete and
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either has a value of SAMPLE_BUFFERS that is greater than zero, then
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the error INVALID_OPERATION is generated if BlitFramebufferANGLE is
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called and the formats of the draw and read framebuffers are not
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identical.
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If either the draw or read framebuffer is framebuffer complete and
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has a value of SAMPLE_BUFFERS that is greater than zero, then the
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error INVALID_OPERATION is generated if BlitFramebufferANGLE is called
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and the specified source and destination dimensions are not
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identical.
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If RenderbufferStorageMultisampleANGLE is called with <target> not
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equal to RENDERBUFFER, the error INVALID_ENUM is generated.
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If RenderbufferStorageMultisampleANGLE is called with an
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<internalformat> that is not listed as one of the color-, depth-
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or stencil-renderable formats in Table 4.5, then the error
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INVALID_ENUM is generated.
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If RenderbufferStorageMultisampleANGLE is called with <width> or
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<height> greater than MAX_RENDERBUFFER_SIZE, then the error
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INVALID_VALUE is generated.
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If RenderbufferStorageMultisampleANGLE is called with a value of
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<samples> that is greater than MAX_SAMPLES_ANGLE or less than zero,
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then the error INVALID_VALUE is generated.
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The error OUT_OF_MEMORY is generated when
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RenderbufferStorageMultisampleANGLE cannot create storage of the
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specified size.
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New State
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Add to table 6.22 (Renderbuffer State)
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Get Value Type Get Command Initial Value Description Section
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------------------------------- ------ -------------------------- ------------- -------------------- -------
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RENDERBUFFER_SAMPLES_ANGLE Z+ GetRenderbufferParameteriv 0 number of samples 4.4.3
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Add to table 6.yy (Framebuffer Dependent Vaues) (added by
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ANGLE_framebuffer_blit), the following new framebuffer dependent state.
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Get Value Type Get Command Minimum Value Description Section
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----------------- ---- ----------- ------------- ------------------- -------
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MAX_SAMPLES_ANGLE Z+ GetIntegerv 1 Maximum number of 4.4.3
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samples supported
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for multisampling
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Issues
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Issues from EXT_framebuffer_multisample have been removed.
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1) What should we call this extension?
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Resolved: ANGLE_framebuffer_blit.
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This extension is a result of a collaboration between Google and
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TransGaming for the open-source ANGLE project. Typically one would
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label a multi-vendor extension as EXT, but EXT_framebuffer_mulitsample
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is already the name for this on Desktop GL. Additionally this
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isn't truely a multi-vendor extension because there is only one
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implementation of this. We'll follow the example of the open-source
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MESA project which uses the project name for the vendor suffix.
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2) How does this extension differ from EXT_framebuffer_multisample?
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This is designed to be a proper subset of EXT_framebuffer_multisample
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functionality as applicable to OpenGL ES 2.0.
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Functionality that is unchanged:
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- creation of multisample renderbuffers.
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- whole buffer multi-sample->single-sample resolve.
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- no format conversions, stretching or flipping supported on multisample blits.
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Additional restrictions on BlitFramebufferANGLE:
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- multisample resolve is only supported on color buffers.
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- no blits to multisample destinations (no single->multi or multi-multi).
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- only entire buffers can be resolved.
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Revision History
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Revision 1, 2010/07/08
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- copied from revision 7 of EXT_framebuffer_multisample
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- removed language that was not relevant to ES2
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- rebase changes against the Open GL ES 2.0 specification
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- added ANGLE-specific restrictions
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Revision 2, 2010/07/19
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- fix missing error code
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Revision 3, 2010/08/06
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- add additional contributors, update implementation status
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- disallow negative samples
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