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Commit 59c2f7d4 by daniel@transgaming.com
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Updates to MRT extension.

Trac #21120 01/30/2013 dgkoch add issue 6 and clear interactions renamed to EXT_draw_buffers based on feedback changed resolution of issue 3. git-svn-id: https://angleproject.googlecode.com/svn/trunk@1806 736b8ea6-26fd-11df-bfd4-992fa37f6226
parent 61267981
Showing with 160 additions and 113 deletions
extensions/ANGLE_multiple_render_targets.txt
Name Name
ANGLE_multiple_render_targets EXT_draw_buffers
Name Strings Name Strings
GL_ANGLE_multiple_render_targets GL_EXT_draw_buffers
Contributors Contributors
...@@ -17,20 +17,22 @@ Contributors ...@@ -17,20 +17,22 @@ Contributors
Daniel Koch, TransGaming Inc. Daniel Koch, TransGaming Inc.
Alastair Patrick, Google Inc. Alastair Patrick, Google Inc.
Kenneth Russell, Google Inc. Kenneth Russell, Google Inc.
Members of the WebGL working group Greg Roth, NVIDIA Corporation
Ben Bowman, Imagination Technologies
Members of the WebGL and OpenGL ES working groups
Contact Contact
Daniel Koch <daniel> <at> <transgaming> <dot> <com> Daniel Koch (daniel 'at' transgaming.com)
Status Status
Incomplete -- do not implement! Draft Complete
Version Version
Last Modified Date: January 23, 2013 Last Modified Date: January 30, 2013
Revision: #6 Revision: #7
Number Number
...@@ -58,60 +60,60 @@ Overview ...@@ -58,60 +60,60 @@ Overview
New Procedures and Functions New Procedures and Functions
void DrawBuffersANGLE(sizei n, const enum *bufs); void DrawBuffersEXT(sizei n, const enum *bufs);
New Tokens New Tokens
Accepted by the <pname> parameter of GetIntegerv: Accepted by the <pname> parameter of GetIntegerv:
MAX_COLOR_ATTACHMENTS_ANGLE 0x8CDF MAX_COLOR_ATTACHMENTS_EXT 0x8CDF
Accepted by the <pname> parameters of GetIntegerv and GetFloatv: Accepted by the <pname> parameters of GetIntegerv and GetFloatv:
MAX_DRAW_BUFFERS_ANGLE 0x8824 MAX_DRAW_BUFFERS_EXT 0x8824
DRAW_BUFFER0_ANGLE 0x8825 DRAW_BUFFER0_EXT 0x8825
DRAW_BUFFER1_ANGLE 0x8826 DRAW_BUFFER1_EXT 0x8826
DRAW_BUFFER2_ANGLE 0x8827 DRAW_BUFFER2_EXT 0x8827
DRAW_BUFFER3_ANGLE 0x8828 DRAW_BUFFER3_EXT 0x8828
DRAW_BUFFER4_ANGLE 0x8829 DRAW_BUFFER4_EXT 0x8829
DRAW_BUFFER5_ANGLE 0x882A DRAW_BUFFER5_EXT 0x882A
DRAW_BUFFER6_ANGLE 0x882B DRAW_BUFFER6_EXT 0x882B
DRAW_BUFFER7_ANGLE 0x882C DRAW_BUFFER7_EXT 0x882C
DRAW_BUFFER8_ANGLE 0x882D DRAW_BUFFER8_EXT 0x882D
DRAW_BUFFER9_ANGLE 0x882E DRAW_BUFFER9_EXT 0x882E
DRAW_BUFFER10_ANGLE 0x882F DRAW_BUFFER10_EXT 0x882F
DRAW_BUFFER11_ANGLE 0x8830 DRAW_BUFFER11_EXT 0x8830
DRAW_BUFFER12_ANGLE 0x8831 DRAW_BUFFER12_EXT 0x8831
DRAW_BUFFER13_ANGLE 0x8832 DRAW_BUFFER13_EXT 0x8832
DRAW_BUFFER14_ANGLE 0x8833 DRAW_BUFFER14_EXT 0x8833
DRAW_BUFFER15_ANGLE 0x8834 DRAW_BUFFER15_EXT 0x8834
Accepted by the <attachment> parameter of FramebufferRenderbuffer, Accepted by the <attachment> parameter of FramebufferRenderbuffer,
FramebufferTexture2D and GetFramebufferAttachmentParameteriv, and by FramebufferTexture2D and GetFramebufferAttachmentParameteriv, and by
the <bufs> parameter of DrawBuffersANGLE: the <bufs> parameter of DrawBuffersEXT:
COLOR_ATTACHMENT0_ANGLE 0x8CE0 COLOR_ATTACHMENT0_EXT 0x8CE0
COLOR_ATTACHMENT1_ANGLE 0x8CE1 COLOR_ATTACHMENT1_EXT 0x8CE1
COLOR_ATTACHMENT2_ANGLE 0x8CE2 COLOR_ATTACHMENT2_EXT 0x8CE2
COLOR_ATTACHMENT3_ANGLE 0x8CE3 COLOR_ATTACHMENT3_EXT 0x8CE3
COLOR_ATTACHMENT4_ANGLE 0x8CE4 COLOR_ATTACHMENT4_EXT 0x8CE4
COLOR_ATTACHMENT5_ANGLE 0x8CE5 COLOR_ATTACHMENT5_EXT 0x8CE5
COLOR_ATTACHMENT6_ANGLE 0x8CE6 COLOR_ATTACHMENT6_EXT 0x8CE6
COLOR_ATTACHMENT7_ANGLE 0x8CE7 COLOR_ATTACHMENT7_EXT 0x8CE7
COLOR_ATTACHMENT8_ANGLE 0x8CE8 COLOR_ATTACHMENT8_EXT 0x8CE8
COLOR_ATTACHMENT9_ANGLE 0x8CE9 COLOR_ATTACHMENT9_EXT 0x8CE9
COLOR_ATTACHMENT10_ANGLE 0x8CEA COLOR_ATTACHMENT10_EXT 0x8CEA
COLOR_ATTACHMENT11_ANGLE 0x8CEB COLOR_ATTACHMENT11_EXT 0x8CEB
COLOR_ATTACHMENT12_ANGLE 0x8CEC COLOR_ATTACHMENT12_EXT 0x8CEC
COLOR_ATTACHMENT13_ANGLE 0x8CED COLOR_ATTACHMENT13_EXT 0x8CED
COLOR_ATTACHMENT14_ANGLE 0x8CEE COLOR_ATTACHMENT14_EXT 0x8CEE
COLOR_ATTACHMENT15_ANGLE 0x8CEF COLOR_ATTACHMENT15_EXT 0x8CEF
The COLOR_ATTACHMENT0_ANGLE constant is equal to the The COLOR_ATTACHMENT0_EXT constant is equal to the
COLOR_ATTACHMENT0 constant. COLOR_ATTACHMENT0 constant.
Each COLOR_ATTACHMENT<i>_ANGLE adheres to COLOR_ATTACHMENT<i>_ANGLE Each COLOR_ATTACHMENT<i>_EXT adheres to COLOR_ATTACHMENT<i>_EXT
= COLOR_ATTACHMENT0_ANGLE + <i>. = COLOR_ATTACHMENT0_EXT + <i>.
Changes to Chapter 3 of the OpenGL ES 2.0 Specification (Rasterization) Changes to Chapter 3 of the OpenGL ES 2.0 Specification (Rasterization)
...@@ -166,18 +168,18 @@ Operations and the Frame Buffer) ...@@ -166,18 +168,18 @@ Operations and the Frame Buffer)
Insert Table 4.3 to Section 4.2.1 (and renumber subsequent tables): Insert Table 4.3 to Section 4.2.1 (and renumber subsequent tables):
Symbolic Constant Meaning Symbolic Constant Meaning
----------------- --------------------- ----------------- ---------------------
NONE No buffer NONE No buffer
COLOR_ATTACHMENT<i>_ANGLE (see caption) Output fragment color to image COLOR_ATTACHMENT<i>_EXT (see caption) Output fragment color to image
attached at color attachment attached at color attachment
point i point i
Table 4.3: Arguments to DrawBuffersANGLE when the context is bound to a Table 4.3: Arguments to DrawBuffersEXT when the context is bound to a
framebuffer object, and the buffers they indicate. <i> in framebuffer object, and the buffers they indicate. <i> in
COLOR_ATTACHMENT<i>_ANGLE may range from zero to the value of COLOR_ATTACHMENT<i>_EXT may range from zero to the value of
MAX_COLOR_ATTACHMENTS_ANGLE minus one. MAX_COLOR_ATTACHMENTS_EXT minus one.
Replace Section 4.2.1, "Selecting a Buffer for Writing" with the following: Replace Section 4.2.1, "Selecting a Buffer for Writing" with the following:
...@@ -185,11 +187,11 @@ Operations and the Frame Buffer) ...@@ -185,11 +187,11 @@ Operations and the Frame Buffer)
single buffered surfaces or into the back buffer for back buffered single buffered surfaces or into the back buffer for back buffered
surfaces as determined when making the context current. To control surfaces as determined when making the context current. To control
the color buffer into which each of the fragment color values is the color buffer into which each of the fragment color values is
written, DrawBuffersANGLE is used. written, DrawBuffersEXT is used.
The command The command
void DrawBuffersANGLE(sizei n, const enum *bufs); void DrawBuffersEXT(sizei n, const enum *bufs);
defines the draw buffers to which all fragment colors are written. defines the draw buffers to which all fragment colors are written.
<n> specifies the number of buffers in <bufs>. <bufs> is a pointer <n> specifies the number of buffers in <bufs>. <bufs> is a pointer
...@@ -207,7 +209,7 @@ Operations and the Frame Buffer) ...@@ -207,7 +209,7 @@ Operations and the Frame Buffer)
and the constant must be BACK or NONE. When draw buffer zero is and the constant must be BACK or NONE. When draw buffer zero is
BACK, color values are written into the sole buffer for single- BACK, color values are written into the sole buffer for single-
buffered contexts, or into the back buffer for double-buffered buffered contexts, or into the back buffer for double-buffered
contexts. If DrawBuffersANGLE is supplied with a constant other than contexts. If DrawBuffersEXT is supplied with a constant other than
BACK and NONE, the error INVALID_OPERATION is generated. BACK and NONE, the error INVALID_OPERATION is generated.
If the GL is bound to a draw framebuffer object, then each of the If the GL is bound to a draw framebuffer object, then each of the
...@@ -219,27 +221,27 @@ Operations and the Frame Buffer) ...@@ -219,27 +221,27 @@ Operations and the Frame Buffer)
The maximum number of draw buffers is implementation-dependent. The The maximum number of draw buffers is implementation-dependent. The
number of draw buffers supported can be queried by calling number of draw buffers supported can be queried by calling
GetIntegerv with the symbolic constant MAX_DRAW_BUFFERS_ANGLE. An GetIntegerv with the symbolic constant MAX_DRAW_BUFFERS_EXT. An
INVALID_VALUE error is generated if <n> is greater than INVALID_VALUE error is generated if <n> is greater than
MAX_DRAW_BUFFERS_ANGLE. MAX_DRAW_BUFFERS_EXT.
If the GL is bound to a draw framebuffer object, the <i>th buffer listed 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 in <bufs> must be COLOR_ATTACHMENT<i>_EXT or NONE. Specifying a
buffer out of order, BACK, or COLOR_ATTACHMENT<m>_ANGLE where <m> is buffer out of order, BACK, or COLOR_ATTACHMENT<m>_EXT where <m> is
greater than or equal to the value of MAX_COLOR_ATTACHMENTS_ANGLE, greater than or equal to the value of MAX_COLOR_ATTACHMENTS_EXT,
will generate the error INVALID_OPERATION. will generate the error INVALID_OPERATION.
If a fragment shader writes to "gl_FragColor", DrawBuffersANGLE If a fragment shader writes to "gl_FragColor", DrawBuffersEXT
specifies the draw buffer, if any, into which the color written to specifies the set of draw buffers into which the color
"gl_FragColor" is written. If a fragment shader writes to written to "gl_FragColor" is written. If a fragment shader writes to
"gl_FragData", DrawBuffersANGLE specifies a set of draw buffers "gl_FragData", DrawBuffersEXT specifies a set of draw buffers
into which each of the multiple output colors defined by these into which each of the multiple output colors defined by these
variables are separately written. If a fragment shader writes to variables are separately written. If a fragment shader writes to
neither "gl_FragColor" nor "gl_FragData" the values of the neither "gl_FragColor" nor "gl_FragData" the values of the
fragment colors following shader execution are undefined, and may fragment colors following shader execution are undefined, and may
differ for each fragment color. differ for each fragment color.
Indicating a buffer or buffers using DrawBuffersANGLE causes Indicating a buffer or buffers using DrawBuffersEXT causes
subsequent pixel color value writes to affect the indicated subsequent pixel color value writes to affect the indicated
buffers. If the GL is bound to a draw framebuffer object and a draw 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 buffer selects an attachment that has no image attached, then that
...@@ -254,7 +256,7 @@ Operations and the Frame Buffer) ...@@ -254,7 +256,7 @@ Operations and the Frame Buffer)
fragment color zero is BACK if there is a default framebuffer fragment color zero is BACK if there is a default framebuffer
associated with the context, otherwise NONE. For framebuffer associated with the context, otherwise NONE. For framebuffer
objects, in the initial state the draw buffer for fragment color objects, in the initial state the draw buffer for fragment color
zero is COLOR_ATTACHMENT0_ANGLE. zero is COLOR_ATTACHMENT0_EXT.
For both the default framebuffer and framebuffer objects, the For both the default framebuffer and framebuffer objects, the
initial state of draw buffers for fragment colors other than zero is initial state of draw buffers for fragment colors other than zero is
...@@ -262,7 +264,30 @@ Operations and the Frame Buffer) ...@@ -262,7 +264,30 @@ Operations and the Frame Buffer)
The value of the draw buffer selected for fragment color <i> can be The value of the draw buffer selected for fragment color <i> can be
queried by calling GetIntegerv with the symbolic constant queried by calling GetIntegerv with the symbolic constant
DRAW_BUFFER<i>_ANGLE." DRAW_BUFFER<i>_EXT."
Modify Section 4.2.3 (Clearing the Buffers) and replace the first
two paragraphs with the following:
"The GL provides a means for setting portions of every pixel in a
particular buffer to the same value. The argument to
void Clear(bitfield buf);
is the bitwise OR of a number of values indicating which buffers are
to be cleared. The values are COLOR_BUFFER_BIT, DEPTH_BUFFER_BIT, and
STENCIL_BUFFER_BIT, indicating the buffers currently enabled for color
writing, the depth buffer, and the stencil buffer (see below),
respectively. The value to which each buffer is cleared depends on
the setting of the clear value for that buffer. If the mask is not a
bitwise OR of the specified values, then the error INVALID_VALUE is
generated.
void ClearColor(clampf r, clampf, g, clampf b, clampf a);
sets the clear value for fixed-point color buffers. Each of the
specified components is clamped to [0, 1] and converted to fixed-point
as described in section 2.1.2 for framebuffer color components."
Replace the second paragraph of Section 4.4.1 (Binding and Managing Replace the second paragraph of Section 4.4.1 (Binding and Managing
Framebuffer Objects) with the following: Framebuffer Objects) with the following:
...@@ -279,14 +304,14 @@ Operations and the Frame Buffer) ...@@ -279,14 +304,14 @@ Operations and the Frame Buffer)
to the unused name. The resulting framebuffer object is a new state to the unused name. The resulting framebuffer object is a new state
vector. There is a number of color attachment points, plus one each vector. There is a number of color attachment points, plus one each
for the depth and stencil attachment points. The number of color attachment for the depth and stencil attachment points. The number of color attachment
points is equal to the value of MAX_COLOR_ATTACHMENTS_ANGLE." points is equal to the value of MAX_COLOR_ATTACHMENTS_EXT."
Replace the third item in the bulleted list in Section 4.4.1 (Binding Replace the third item in the bulleted list in Section 4.4.1 (Binding
and Managing Framebuffer Objects) with the following: and Managing Framebuffer Objects) with the following:
" * The only color buffer bitplanes are the ones defined by the " * The only color buffer bitplanes are the ones defined by the
framebuffer attachments points named COLOR_ATTACHMENT0_ANGLE through framebuffer attachments points named COLOR_ATTACHMENT0_EXT through
COLOR_ATTACHMENT<n>_ANGLE." COLOR_ATTACHMENT<n>_EXT."
Modify Section 4.4.3 (Renderbuffer Objects) in the Modify Section 4.4.3 (Renderbuffer Objects) in the
"Attaching Renderbuffer Images to a Framebuffer" subsection as follows: "Attaching Renderbuffer Images to a Framebuffer" subsection as follows:
...@@ -295,12 +320,12 @@ Operations and the Frame Buffer) ...@@ -295,12 +320,12 @@ Operations and the Frame Buffer)
Name of attachment Name of attachment
--------------------------------------- ---------------------------------------
COLOR_ATTACHMENT<i>_ANGLE (see caption) COLOR_ATTACHMENT<i>_EXT (see caption)
DEPTH_ATTACHMENT DEPTH_ATTACHMENT
STENCIL_ATTACHMENT STENCIL_ATTACHMENT
Table 4.x: Framebuffer attachment points. <i> in COLOR_ATTACHMENT<i>_ANGLE Table 4.x: Framebuffer attachment points. <i> in COLOR_ATTACHMENT<i>_EXT
may range from zero to the value of MAX_COLOR_ATTACHMENTS_ANGLE minus 1. may range from zero to the value of MAX_COLOR_ATTACHMENTS_EXT minus 1.
Modify the third sentence of the paragraph following the definition of Modify the third sentence of the paragraph following the definition of
FramebufferRenderbuffer to be as follows: FramebufferRenderbuffer to be as follows:
...@@ -321,7 +346,7 @@ Operations and the Frame Buffer) ...@@ -321,7 +346,7 @@ Operations and the Frame Buffer)
item in the bulleted list in the "Framebuffer Attachment Completeness" item in the bulleted list in the "Framebuffer Attachment Completeness"
subsection with the following: subsection with the following:
" * If <attachment> is COLOR_ATTACHMENT<i>_ANGLE, then <image> must " * If <attachment> is COLOR_ATTACHMENT<i>_EXT, then <image> must
have a color-renderable internal format." have a color-renderable internal format."
Changes to Chapter 6 of the OpenGL ES 2.0 Specification (State and Changes to Chapter 6 of the OpenGL ES 2.0 Specification (State and
...@@ -337,14 +362,14 @@ Changes to Chapter 3 of the OpenGL ES Shading Language 1.0.17 Specification (Bas ...@@ -337,14 +362,14 @@ Changes to Chapter 3 of the OpenGL ES Shading Language 1.0.17 Specification (Bas
Add a new section: Add a new section:
3.4.1 GL_ANGLE_multiple_render_targets Extension 3.4.1 GL_EXT_draw_buffers Extension
To use the GL_ANGLE_multiple_render_targets extension in a shader it To use the GL_EXT_draw_buffers extension in a shader it
must be enabled using the #extension directive. must be enabled using the #extension directive.
The shading language preprocessor #define The shading language preprocessor #define
GL_ANGLE_multiple_render_targets will be defined to 1, if the GL_EXT_draw_buffers will be defined to 1, if the
GL_ANGLE_multiple_render_targets extension is supported. GL_EXT_draw_buffers extension is supported.
Dependencies on ANGLE_framebuffer_blit and APPLE_framebuffer_multisample: Dependencies on ANGLE_framebuffer_blit and APPLE_framebuffer_multisample:
...@@ -364,19 +389,19 @@ Dependencies on ANGLE_framebuffer_blit and APPLE_framebuffer_multisample: ...@@ -364,19 +389,19 @@ Dependencies on ANGLE_framebuffer_blit and APPLE_framebuffer_multisample:
Errors Errors
The INVALID_OPERATION error is generated if DrawBuffersANGLE is called The INVALID_OPERATION error is generated if DrawBuffersEXT is called
when the default framebuffer is bound and any of the following conditions when the default framebuffer is bound and any of the following conditions
hold: hold:
- <n> is greater than 1 and less than MAX_DRAW_BUFFERS_ANGLE, - <n> is greater than 1 and less than MAX_DRAW_BUFFERS_EXT,
- <bufs> contains a value other than BACK or NONE. - <bufs> contains a value other than BACK or NONE.
The INVALID_OPERATION error is generated if DrawBuffersANGLE is called The INVALID_OPERATION error is generated if DrawBuffersEXT is called
when bound to a draw framebuffer object and any of the following when bound to a draw framebuffer object and any of the following
conditions hold: conditions hold:
- the <i>th value in <bufs> is not COLOR_ATTACHMENT<i>_ANGLE or NONE. - the <i>th value in <bufs> is not COLOR_ATTACHMENT<i>_EXT or NONE.
The INVALID_VALUE error is generated if DrawBuffersANGLE is called The INVALID_VALUE error is generated if DrawBuffersEXT is called
with a value of <n> which is greater than MAX_DRAW_BUFFERS_ANGLE. with a value of <n> which is greater than MAX_DRAW_BUFFERS_EXT.
The INVALID_ENUM error is generated by FramebufferRenderbuffer if The INVALID_ENUM error is generated by FramebufferRenderbuffer if
the <attachment> parameter is not one of the values listed in Table 4.x. the <attachment> parameter is not one of the values listed in Table 4.x.
...@@ -391,31 +416,36 @@ New State ...@@ -391,31 +416,36 @@ New State
Add Table 6.X Framebuffer (State per framebuffer object): Add Table 6.X Framebuffer (State per framebuffer object):
State Type Get Command Initial Value Description State Type Get Command Initial Value Description
--------------- ---- ------------ ------------- ----------- ------------------ ---- ------------ ------------- -----------
DRAW_BUFFER<i>_ANGLE Z10* GetIntegerv see 4.2.1 Draw buffer selected DRAW_BUFFER<i>_EXT Z10* GetIntegerv see 4.2.1 Draw buffer selected
for fragment color i for fragment color i
Add to Table 6.18 (Implementation Dependent Values) Add to Table 6.18 (Implementation Dependent Values)
Get value Type Get Cmnd Minimum Value Description Sec. Get value Type Get Cmnd Minimum Value Description Sec.
------------------------ ---- ----------- ------------- ----------- ----- -------------------- ---- ----------- ------------- ----------- -----
MAX_DRAW_BUFFERS_ANGLE Z+ GetIntegerv 1 Maximum number of 4.2.1 MAX_DRAW_BUFFERS_EXT Z+ GetIntegerv 1 Maximum number of 4.2.1
active draw buffers active draw buffers
MAX_COLOR_ATTACHMENTS_ANGLE Z+ GetIntegerv 1 Number of framebuffer 4.4.1 MAX_COLOR_ATTACHMENTS_EXT Z+ GetIntegerv 1 Number of framebuffer 4.4.1
color attachment points color attachment points
Issues Issues
See ARB_draw_buffers for relevant issues. See ARB_draw_buffers for relevant issues.
1) Differences from NV_draw_buffers + NV_fbo_color_attachments? 1) What are the differences between this extension and NV_draw_buffers
+ NV_fbo_color_attachments?
- adds interactions with blit_framebuffer and separate draw/read binding points RESOLVED. This extension:
- MAX limits are global instead of per-fbo (see Issue 2) - adds interactions with blit_framebuffer and the separate
- no broadcast from gl_FragColor (see Issue 3) draw/read binding points
- can be used to with default framebuffer to set NONE/BACK (see Issue 4) - The draw buffer and color attachment limits are global instead
of per-fbo (see Issue 2)
- can be used to with default framebuffer to set NONE/BACK (see Issue 4)
- retains the ordering restrictions on color attachments that are
imposed by ES 3.0.
2) Should the MAX_DRAW_BUFFERS_ANGLE and MAX_COLOR_ATTACHMENTS_ANGLE limits 2) Should the MAX_DRAW_BUFFERS_EXT and MAX_COLOR_ATTACHMENTS_EXT limits
be per-framebuffer values or implementation dependent constants? be per-framebuffer values or implementation dependent constants?
DISCUSSION: In ARB_draw_buffers this was per-context (see Issue 2). DISCUSSION: In ARB_draw_buffers this was per-context (see Issue 2).
...@@ -436,10 +466,10 @@ Issues ...@@ -436,10 +466,10 @@ Issues
single-sampled attachments are present. single-sampled attachments are present.
RESOLVED. Make this global context state as this is most consistent RESOLVED. Make this global context state as this is most consistent
with GLES 3.0 and updated GL drivers. Unfortunately this means that a with GLES 3.0 and updated GL drivers. In an implementation cannot
D3D9-based implementation of this extension is not possible since D3D9 support multisampling in conjunction with multiple color attachments,
does not support multisampled MRTs. Perhaps such an implementation could perhaps such an implementation could report FBO incomplete in this
report FBO incomplete in this situation, but that seems less than desirable. situation, but this is less than desirable.
3) Should we support broadcast from gl_FragColor to all gl_FragData[x] 3) Should we support broadcast from gl_FragColor to all gl_FragData[x]
or should it be synonymous with gl_FragData[0]? or should it be synonymous with gl_FragData[0]?
...@@ -454,10 +484,18 @@ Issues ...@@ -454,10 +484,18 @@ Issues
writes to gl_FragColor with replicated writes to all possible gl_FragData writes to gl_FragColor with replicated writes to all possible gl_FragData
locations when this extension is enabled. locations when this extension is enabled.
RESOLVED: Broadcast from gl_FragColor to all enabledMRT buffers is not RESOLVED: Writes to gl_FragColor are broadcast to all enabled color
supported. A shader author must write gl_FragData[x] if they want to use MRT buffers. ES 3.0 using ESSL 1.0 doesn't support broadcast because
ESSL 1.0 was not extended to have multiple color outputs (but that is
4) Should we allow DrawBuffersANGLE to be called when the default FBO is bound? what this extension adds). ESSL 3.0 doesn't support the broadcast because
it doesn't have the gl_FragColor variable at all, and only has user-
defined out variables. This extension extends ESSL 1.0 to have multiple
color outputs. Broadcasting from gl_FragColor to all enabled color
buffers is the most consistent with existing draw buffer extensions to
date (both NV_draw_buffers and desktop GL).
4) Should we allow DrawBuffersEXT to be called when the default FBO is
bound?
DISCUSSION: NV_draw_buffers specifies that DrawBuffersNV errors with DISCUSSION: NV_draw_buffers specifies that DrawBuffersNV errors with
INVALID_OPERATION when the default FBO is bound. OpenGL ES 3.0 allows INVALID_OPERATION when the default FBO is bound. OpenGL ES 3.0 allows
...@@ -466,7 +504,7 @@ Issues ...@@ -466,7 +504,7 @@ Issues
An implementation that does not natively support disabling the drawbuffer An implementation that does not natively support disabling the drawbuffer
on the default FBO could emulate this by disabling color writes. on the default FBO could emulate this by disabling color writes.
RESOLVED: Allow DrawBuffersANGLE to be called for the default FBO. This RESOLVED: Allow DrawBuffersEXT to be called for the default FBO. This
is more forward looking and is compatible with ES 3.0. is more forward looking and is compatible with ES 3.0.
5) What are the requirements on the color attachment sizes and formats? 5) What are the requirements on the color attachment sizes and formats?
...@@ -478,8 +516,17 @@ Issues ...@@ -478,8 +516,17 @@ Issues
This extension does not lift those requirements, and failing to meet This extension does not lift those requirements, and failing to meet
them will result in an incomplete FBO. them will result in an incomplete FBO.
6) Does this have any interactions with glClear?
RESOLVED: Yes. When multiple color buffers are enabled for writing,
glClear clears all of the color buffers. Added language clarifying
that glClear and glClearColor may affect multiple color buffers.
Revision History Revision History
01/30/2013 dgkoch add issue 6 and clear interactions
renamed to EXT_draw_buffers based on feedback
changed resolution of issue 3.
01/23/2013 dgkoch add resolutions to issues 2-4. 01/23/2013 dgkoch add resolutions to issues 2-4.
add issue 5. add issue 5.
Add Table 4.x and update various explicit Add Table 4.x and update various explicit
......
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