зеркало из https://github.com/mozilla/gecko-dev.git
384 строки
17 KiB
Plaintext
384 строки
17 KiB
Plaintext
Name
|
|
|
|
ANGLE_multiple_render_targets
|
|
|
|
Name Strings
|
|
|
|
GL_ANGLE_multiple_render_targets
|
|
|
|
Contributors
|
|
|
|
Contributors to GL_NV_draw_buffers
|
|
Contributors to GL_NV_fbo_color_attachments
|
|
Contributors to the OpenGL ES 2.0 specification
|
|
Contributors to the OpenGLSL ES 1.0.17 specification
|
|
Contributors to the OpenGL ES 3.0 specification
|
|
Nicolas Capens, TransGaming Inc.
|
|
Daniel Koch, TransGaming Inc.
|
|
Alastair Patrick, Google Inc.
|
|
Members of the WebGL working group
|
|
|
|
Contact
|
|
|
|
Daniel Koch <daniel> <at> <transgaming> <dot> <com>
|
|
|
|
Status
|
|
|
|
Incomplete -- do not implement!
|
|
|
|
Version
|
|
|
|
Last Modified Data: November 13, 2012
|
|
Revision: #5
|
|
|
|
Number
|
|
|
|
TBD
|
|
|
|
Dependencies
|
|
|
|
OpenGL ES 2.0 is required.
|
|
|
|
The extension is written against the OpenGL ES 2.0 specification.
|
|
|
|
ANGLE_framebuffer_blit affects the definition of this extension.
|
|
APPLE_framebuffer_multisample affects the definitin of this extension.
|
|
|
|
Overview
|
|
|
|
This extension increases the number of available framebuffer object
|
|
color attachment points, extends OpenGL ES 2.0 to allow multiple output
|
|
colors, and provides a mechanism for directing those outputs to
|
|
multiple color buffers.
|
|
|
|
This extension is similar to the combination of the GL_NV_draw_buffers
|
|
and GL_NV_fbo_color_attachments extensions, but imposes certain
|
|
restrictions informed by the OpenGL ES 3.0 API.
|
|
|
|
New Procedures and Functions
|
|
|
|
void DrawBuffersANGLE(sizei n, const enum *bufs);
|
|
|
|
New Tokens
|
|
|
|
Accepted by the <pname> parameter of GetIntegerv:
|
|
|
|
MAX_COLOR_ATTACHMENTS_ANGLE 0x8CDF
|
|
|
|
Accepted by the <pname> parameters of GetIntegerv and GetFloatv:
|
|
|
|
MAX_DRAW_BUFFERS_ANGLE 0x8824
|
|
DRAW_BUFFER0_ANGLE 0x8825
|
|
DRAW_BUFFER1_ANGLE 0x8826
|
|
DRAW_BUFFER2_ANGLE 0x8827
|
|
DRAW_BUFFER3_ANGLE 0x8828
|
|
DRAW_BUFFER4_ANGLE 0x8829
|
|
DRAW_BUFFER5_ANGLE 0x882A
|
|
DRAW_BUFFER6_ANGLE 0x882B
|
|
DRAW_BUFFER7_ANGLE 0x882C
|
|
DRAW_BUFFER8_ANGLE 0x882D
|
|
DRAW_BUFFER9_ANGLE 0x882E
|
|
DRAW_BUFFER10_ANGLE 0x882F
|
|
DRAW_BUFFER11_ANGLE 0x8830
|
|
DRAW_BUFFER12_ANGLE 0x8831
|
|
DRAW_BUFFER13_ANGLE 0x8832
|
|
DRAW_BUFFER14_ANGLE 0x8833
|
|
DRAW_BUFFER15_ANGLE 0x8834
|
|
|
|
Accepted by the <attachment> parameter of FramebufferRenderbuffer,
|
|
FramebufferTexture2D and GetFramebufferAttachmentParameteriv, and by
|
|
the <bufs> parameter of DrawBuffersANGLE:
|
|
|
|
COLOR_ATTACHMENT0_ANGLE 0x8CE0
|
|
COLOR_ATTACHMENT1_ANGLE 0x8CE1
|
|
COLOR_ATTACHMENT2_ANGLE 0x8CE2
|
|
COLOR_ATTACHMENT3_ANGLE 0x8CE3
|
|
COLOR_ATTACHMENT4_ANGLE 0x8CE4
|
|
COLOR_ATTACHMENT5_ANGLE 0x8CE5
|
|
COLOR_ATTACHMENT6_ANGLE 0x8CE6
|
|
COLOR_ATTACHMENT7_ANGLE 0x8CE7
|
|
COLOR_ATTACHMENT8_ANGLE 0x8CE8
|
|
COLOR_ATTACHMENT9_ANGLE 0x8CE9
|
|
COLOR_ATTACHMENT10_ANGLE 0x8CEA
|
|
COLOR_ATTACHMENT11_ANGLE 0x8CEB
|
|
COLOR_ATTACHMENT12_ANGLE 0x8CEC
|
|
COLOR_ATTACHMENT13_ANGLE 0x8CED
|
|
COLOR_ATTACHMENT14_ANGLE 0x8CEE
|
|
COLOR_ATTACHMENT15_ANGLE 0x8CEF
|
|
|
|
The COLOR_ATTACHMENT0_ANGLE constant is equal to the
|
|
COLOR_ATTACHMENT0 constant.
|
|
|
|
Each COLOR_ATTACHMENT<i>_ANGLE adheres to COLOR_ATTACHMENT<i>_ANGLE
|
|
= COLOR_ATTACHMENT0_ANGLE + <i>.
|
|
|
|
Changes to Chapter 3 of the OpenGL ES 2.0 Specification (Rasterization)
|
|
|
|
Section 3.2, (Multisampling). Replace the second paragraph:
|
|
|
|
An additional buffer, called the multisample buffer, is added to the
|
|
window system-provided framebuffer. Pixel sample values, including
|
|
color, depth, and stencil values, are stored in this buffer. Samples
|
|
contain separate color values for each fragment color. When the
|
|
window system-provided framebuffer includes a multisample buffer, it
|
|
does not include depth or stencil buffers, even if the multisample
|
|
buffer does not store depth or stencil values. Color buffers do
|
|
coexist with the multisample buffer, however.
|
|
|
|
Section 3.8.2, (Shader Execution) Replace subsection "Shader
|
|
Outputs":
|
|
|
|
The OpenGL ES Shading Language specification describes the values
|
|
that may be output by a fragment shader. These are gl_FragColor and
|
|
gl_FragData[n]. The final fragment color values or the final
|
|
fragment data values written by a fragment shader are clamped to the
|
|
range [0, 1] and then converted to fixed-point as described in
|
|
section 2.1.2 for framebuffer color components.
|
|
|
|
Writing to gl_FragColor specifies the fragment color (color number
|
|
zero) that will be used by subsequent stages of the pipeline.
|
|
Writing to gl_FragData[n] specifies the value of fragment color
|
|
number n. Any colors, or color components, associated with a
|
|
fragment that are not written by the fragment shader are undefined.
|
|
A fragment shader may not statically assign values to both
|
|
gl_FragColor and gl_FragData. In this case, a compile or link error
|
|
will result. A shader statically assigns a value to a variable if,
|
|
after preprocessing, it contains a statement that would write to the
|
|
variable, whether or not run-time flow of control will cause that
|
|
statement to be executed.
|
|
|
|
Changes to Chapter 4 of the OpenGL ES 2.0 Specification (Per-Fragment
|
|
Operations and the Frame Buffer)
|
|
|
|
Insert Table 4.3 (and renumber subsequent tables): Arguments to
|
|
DrawBuffersANGLE when the context is bound to a framebuffer
|
|
object, and the buffers they indicate. <i> in
|
|
COLOR_ATTACHMENT<i>_ANGLE may range from zero to the value of
|
|
MAX_COLOR_ATTACHMENTS_ANGLE minus one.
|
|
|
|
Symbolic Constant Meaning
|
|
----------------- ---------------------
|
|
NONE No buffer
|
|
|
|
COLOR_ATTACHMENT<i>_ANGLE (see caption) Output fragment color to image
|
|
attached at color attachment
|
|
point i
|
|
|
|
|
|
Replace Section 4.2.1, "Selecting a Buffer for Writing" with the following:
|
|
|
|
"By default, color values are written into the front buffer for
|
|
single buffered surfaces or into the back buffer for back buffered
|
|
surfaces as determined when making the context current. To control
|
|
the color buffer into which each of the fragment color values is
|
|
written, DrawBuffersANGLE is used.
|
|
|
|
The command
|
|
|
|
void DrawBuffersANGLE(sizei n, const enum *bufs);
|
|
|
|
defines the draw buffers to which all fragment colors are written.
|
|
<n> specifies the number of buffers in <bufs>. <bufs> is a pointer
|
|
to an array of symbolic constants specifying the buffer to which
|
|
each fragment color is written.
|
|
|
|
Each buffer listed in <bufs> must be BACK, NONE, or one of the
|
|
values from table 4.3. Further, acceptable values for the constants
|
|
in <bufs> depend on whether the GL is using the default framebuffer
|
|
(i.e., DRAW_FRAMEBUFFER_BINDING is zero), or a framebuffer object
|
|
(i.e., DRAW_FRAMEBUFFER_BINDING is non-zero). For more information
|
|
about framebuffer objects, see section 4.4.
|
|
|
|
If the GL is bound to the default framebuffer, then <n> must be 1
|
|
and the constant must be BACK or NONE. When draw buffer zero is
|
|
BACK, color values are written into the sole buffer for single-
|
|
buffered contexts, or into the back buffer for double-buffered
|
|
contexts. If DrawBuffersANGLE is supplied with a constant other than
|
|
BACK and NONE, the error INVALID_OPERATION is generated.
|
|
|
|
If the GL is bound to a draw framebuffer object, then each of the
|
|
constants must be one of the values listed in table 4.3.
|
|
|
|
In both cases, the draw buffers being defined correspond in order to
|
|
the respective fragment colors. The draw buffer for fragment
|
|
colors beyond <n> is set to NONE.
|
|
|
|
The maximum number of draw buffers is implementation-dependent. The
|
|
number of draw buffers supported can be queried by calling
|
|
GetIntegerv with the symbolic constant MAX_DRAW_BUFFERS_ANGLE. An
|
|
INVALID_VALUE error is generated if <n> is greater than
|
|
MAX_DRAW_BUFFERS_ANGLE.
|
|
|
|
If the GL is bound to a draw framebuffer object, the <i>th buffer listed
|
|
in <bufs> must be COLOR_ATTACHMENT<i>_ANGLE or NONE. Specifying a
|
|
buffer out of order, BACK, or COLOR_ATTACHMENT<m>_ANGLE where <m> is
|
|
greater than or equal to the value of MAX_COLOR_ATTACHMENTS_ANGLE,
|
|
will generate the error INVALID_OPERATION.
|
|
|
|
If a fragment shader writes to "gl_FragColor", DrawBuffersANGLE
|
|
specifies a set of draw buffers into which the color written to
|
|
"gl_FragColor" is written. If a fragment shader writes to
|
|
"gl_FragData", DrawBuffersANGLE specifies a set of draw buffers
|
|
into which each of the multiple output colors defined by these
|
|
variables are separately written. If a fragment shader writes to
|
|
neither "gl_FragColor" nor "gl_FragData" the values of the
|
|
fragment colors following shader execution are undefined, and may
|
|
differ for each fragment color.
|
|
|
|
Indicating a buffer or buffers using DrawBuffersANGLE causes
|
|
subsequent pixel color value writes to affect the indicated
|
|
buffers. If the GL is bound to a draw framebuffer object and a draw
|
|
buffer selects an attachment that has no image attached, then that
|
|
fragment color is not written.
|
|
|
|
Specifying NONE as the draw buffer for a fragment color will inhibit
|
|
that fragment color from being written.
|
|
|
|
The state required to handle color buffer selection for each
|
|
framebuffer is an integer for each supported fragment color. For the
|
|
default framebuffer, in the initial state the draw buffer for
|
|
fragment color zero is BACK if there is a default framebuffer
|
|
associated with the context, otherwise NONE. For framebuffer
|
|
objects, in the initial state the draw buffer for fragment color
|
|
zero is COLOR_ATTACHMENT0_ANGLE.
|
|
|
|
For both the default framebuffer and framebuffer objects, the
|
|
initial state of draw buffers for fragment colors other than zero is
|
|
NONE.
|
|
|
|
The value of the draw buffer selected for fragment color <i> can be
|
|
queried by calling GetIntegerv with the symbolic constant
|
|
DRAW_BUFFER<i>_ANGLE."
|
|
|
|
Replace the second paragraph of Section 4.4.1 (Binding and Managing
|
|
Framebuffer Objects) with the following:
|
|
|
|
"The namespace for framebuffer objects is the unsigned integers, with
|
|
zero reserved by OpenGL ES to refer to the default framebuffer. A
|
|
framebuffer object is created by binding an unused name to the
|
|
target FRAMEBUFFER, DRAW_FRAMEBUFFER, or READ_FRAMEBUFFER. The binding
|
|
is effected by calling
|
|
|
|
void BindFramebuffer(enum target, uint framebuffer);
|
|
|
|
with <target> set the desired framebuffer target and <framebuffer> set
|
|
to the unused name. The resulting framebuffer object is a new state
|
|
vector. There is a number of color attachment points, plus one each
|
|
for the depth and stencil attachment points. The number of color attachment
|
|
points is equal to the value of MAX_COLOR_ATTACHMENTS_ANGLE."
|
|
|
|
Changes to Chapter 3 of the OpenGL ES Shading Language 1.0.17 Specification (Basics)
|
|
|
|
Add a new section:
|
|
|
|
3.4.1 GL_ANGLE_multiple_render_targets Extension
|
|
|
|
To use the GL_ANGLE_multiple_render_targets extension in a shader it
|
|
must be enabled using the #extension directive.
|
|
|
|
The shading language preprocessor #define
|
|
GL_ANGLE_multiple_render_targets will be defined to 1, if the
|
|
GL_ANGLE_multiple_render_targets extension is supported.
|
|
|
|
Dependencies on ANGLE_framebuffer_blit and APPLE_framebuffer_multisample:
|
|
|
|
If neither ANGLE_framebuffer_blit nor APPLE_framebuffer_multisample are
|
|
supported, then all references to "draw framebuffers" should be replaced
|
|
with references to "framebuffers". References to DRAW_FRAMEBUFFER_BINDING
|
|
should be replaced with references to FRAMEBUFFER_BINDING. References to
|
|
DRAW_FRAMEBUFFER and READ_FRAMEBUFFER should be removed.
|
|
|
|
If ANGLE_framebuffer_blit is supported, DRAW_FRAMEBUFFER_BINDING, DRAW_FRAMEBUFFER
|
|
and READ_FRAMEBUFFER all refer to corresponding _ANGLE suffixed names
|
|
(they have the same token values).
|
|
|
|
If APPLE_framebuffer_multisample is supported, DRAW_FRAMEBUFFER_BINDING,
|
|
DRAW_FRAMEBUFFER and READ_FRAMEBUFFER all refer to the corresponding _APPLE
|
|
suffixed names (they have the same token values).
|
|
|
|
Errors
|
|
|
|
<TBD>
|
|
|
|
New State
|
|
|
|
Add Table 6.X Framebuffer (State per framebuffer object):
|
|
|
|
State Type Get Command Initial Value Description
|
|
--------------- ---- ------------ ------------- -----------
|
|
DRAW_BUFFER<i>_ANGLE Z10* GetIntegerv see 4.2.1 Draw buffer selected
|
|
for fragment color i
|
|
|
|
Add to Table 6.18 (Implementation Dependent Values)
|
|
|
|
Get value Type Get Cmnd Minimum Value Description Sec.
|
|
------------------------ ---- ----------- ------------- ----------- -----
|
|
MAX_DRAW_BUFFERS_ANGLE Z+ GetIntegerv 1 Maximum number of 4.2.1
|
|
active draw buffers
|
|
MAX_COLOR_ATTACHMENTS_ANGLE Z+ GetIntegerv 1 Number of framebuffer 4.4.1
|
|
color attachment points
|
|
Issues
|
|
|
|
See ARB_draw_buffers for relevant issues.
|
|
|
|
1) Differences from NV_draw_buffers + NV_fbo_color_attachments?
|
|
|
|
- interactions with blit_framebuffer
|
|
- MAX limits are global instead of per-fbo (TBD - Issue 2)
|
|
- no broadcast from gl_FragColor (TBD - Issue 3)
|
|
- can be used to with default framebuffer to set NONE/BACK (TBD - Issue 4)
|
|
|
|
2) Should the MAX_DRAW_BUFFERS_ANGLE and MAX_COLOR_ATTACHMENTS_ANGLE limits
|
|
be per-framebuffer values or implementation dependent constants?
|
|
|
|
DISCUSSION: In ARB_draw_buffers this was per-context (see Issue 2).
|
|
EXT_framebuffer_object (and subsequently ARB_framebuffer_object, and GL 3.0
|
|
through GL 4.2) made these queries framebuffer-dependent.
|
|
However GL in 4.3 and GLES 3.0, these limits were moved from
|
|
framebuffer-dependent state to implementation-dependent state after
|
|
much discussion (Bug 7990).
|
|
|
|
NV_draw_buffers has MAX_DRAW_BUFFERS listed as per-framebuffer state,
|
|
but NV_fbo_color_attachments has MAX_COLOR_ATTACHMENTS as an
|
|
implementation-dependent constant.
|
|
|
|
This is relevant because some implementations are not able to support
|
|
multisampling in conjuction with multiple color attachments. If the
|
|
query is per-framebuffer, they can report a maximum of one attachment
|
|
when there are multisampled attachments, but a higher limit when only
|
|
single-sampled attachments are present.
|
|
|
|
3) Should we support broadcast from gl_FragColor to all gl_FragData[x]
|
|
or should it be synonymous with gl_FragData[0]?
|
|
|
|
DISCUSSION: With NV_draw_buffers, writing to gl_FragColor writes to all
|
|
the enabled draw buffers (ie broadcast). In OpenGL ES 3.0 when using
|
|
ESSL 1.0, gl_FragColor is equivalent to writing a single output to
|
|
gl_FragData[0] and multiple outputs are not possible. When using ESSL 3.0,
|
|
only user-defined out variables may be used.
|
|
|
|
If broadcast is supported, some implementations may have to replace
|
|
writes to gl_FragColor with replicated writes to all possible gl_FragData
|
|
locations when this extension is enabled.
|
|
|
|
4) Should we allow DrawBuffersANGLE to be called when the default FBO is bound?
|
|
|
|
DISCUSSION: NV_draw_buffers specifies that DrawBuffersNV errors with
|
|
INVALID_OPERATION when the default FBO is bound. OpenGL ES 3.0 allows
|
|
DrawBuffers to toggle between BACK and NONE on the default FBO.
|
|
|
|
An implementation that does not natively support disabling the drawbuffer
|
|
on the default FBO could emulate this by disabling color writes.
|
|
|
|
|
|
Revision History
|
|
|
|
11/13/2012 dgkoch add revision history
|
|
add text from updated ES 3.0 spec
|
|
add issues for discussion
|
|
10/16/2012 kbr update name string
|
|
10/16/2012 kbr remove restrition requiring draw buffer 0 to be non-NULL
|
|
10/12/2012 kbr remove references to GetDoublev and ReadBuffer
|
|
10/11/2012 kbr initial draft extension
|
|
|