Name
NV_packed_float
NV_packed_float_linear
Name Strings
GL_NV_packed_float
GL_NV_packed_float_linear
Contributors
Mark J. Kilgard, NVIDIA
Mathias Heyer, NVIDIA
Koji Ashida, NVIDIA
Greg Roth, NVIDIA
Contact
Mathias Heyer, NVIDIA (mheyer 'at' nvidia.com)
Status
Complete
Version
Last Modified: 2012/09/26
NVIDIA Revision: 3
Number
OpenGL ES Extension #127
Dependencies
Written against the OpenGL ES 2.0.25 (Nov. 2010) Specification.
EXT_color_buffer_half_float affects the definition of this
specification.
OES_texture_half_float affects the defintion of this specification.
NV_framebuffer_multisample affects the defintion of this
specification.
NV_texture_array affects the defintion of this specification.
EXT_texture_storage affects the defintion of this specification.
Overview
This extension adds a new 3-component floating-point texture format
that fits within a single 32-bit word. This format stores 5 bits
of biased exponent per component in the same manner as 16-bit
floating-point formats, but rather than 10 mantissa bits, the red,
green, and blue components have 6, 6, and 5 bits respectively.
Each mantissa is assumed to have an implied leading one except in the
denorm exponent case. There is no sign bit so only non-negative
values can be represented. Positive infinity, positive denorms,
and positive NaN values are representable. The value of the fourth
component returned by a texture fetch is always 1.0.
This extension also provides support for rendering into an unsigned
floating-point rendering format with the assumption that the texture
format described above could also be advertised as an unsigned
floating-point format for rendering.
The extension also provides a pixel external format for specifying
packed float values directly.
New Tokens
Accepted by the parameter of RenderbufferStorage
and RenderBufferStorageMultisampleNV, TexStorage2DEXT and
TexStorage3DEXT:
R11F_G11F_B10F_NV 0x8C3A
Accepted by the parameter of ReadPixels, TexImage2D,
TexSubImage2D, TexImage3DNV, TexSubImage3DNV:
UNSIGNED_INT_10F_11F_11F_REV_NV 0x8C3B
Changes to Chapter 2 of the OpenGL ES 2.0.25 Specification
(OpenGL Operation)
Add two new sections after Section "Floating-Point Computation":
"Unsigned 11-Bit Floating-Point Numbers"
An unsigned 11-bit floating-point number has no sign bit, a 5-bit
exponent (E), and a 6-bit mantissa (M). The value of an unsigned
11-bit floating-point number (represented as an 11-bit unsigned
integer N) is determined by the following:
0.0, if E == 0 and M == 0,
2^-14 * (M / 64), if E == 0 and M != 0,
2^(E-15) * (1 + M/64), if 0 < E < 31,
INF, if E == 31 and M == 0, or
NaN, if E == 31 and M != 0,
where
E = floor(N / 64), and
M = N mod 64.
Implementations are also allowed to use any of the following
alternative encodings:
0.0, if E == 0 and M != 0
2^(E-15) * (1 + M/64) if E == 31 and M == 0
2^(E-15) * (1 + M/64) if E == 31 and M != 0
When a floating-point value is converted to an unsigned 11-bit
floating-point representation, finite values are rounded to the
closet representable finite value. While less accurate,
implementations are allowed to always round in the direction of
zero. This means negative values are converted to zero.
Likewise, finite positive values greater than 65024 (the maximum
finite representable unsigned 11-bit floating-point value) are
converted to 65024. Additionally: negative infinity is converted
to zero; positive infinity is converted to positive infinity; and
both positive and negative NaN are converted to positive NaN.
Any representable unsigned 11-bit floating-point value is legal
as input to a GL command that accepts 11-bit floating-point data.
The result of providing a value that is not a floating-point
number (such as infinity or NaN) to such a command is unspecified,
but must not lead to GL interruption or termination. Providing a
denormalized number or negative zero to GL must yield predictable
results.
"Unsigned 10-Bit Floating-Point Numbers"
An unsigned 10-bit floating-point number has no sign bit, a 5-bit
exponent (E), and a 5-bit mantissa (M). The value of an unsigned
10-bit floating-point number (represented as an 10-bit unsigned
integer N) is determined by the following:
0.0, if E == 0 and M == 0,
2^-14 * (M / 32), if E == 0 and M != 0,
2^(E-15) * (1 + M/32), if 0 < E < 31,
INF, if E == 31 and M == 0, or
NaN, if E == 31 and M != 0,
where
E = floor(N / 32), and
M = N mod 32.
When a floating-point value is converted to an unsigned 10-bit
floating-point representation, finite values are rounded to the
closet representable finite value. While less accurate,
implementations are allowed to always round in the direction of
zero. This means negative values are converted to zero.
Likewise, finite positive values greater than 64512 (the maximum
finite representable unsigned 10-bit floating-point value) are
converted to 64512. Additionally: negative infinity is converted
to zero; positive infinity is converted to positive infinity; and
both positive and negative NaN are converted to positive NaN.
Any representable unsigned 10-bit floating-point value is legal
as input to a GL command that accepts 10-bit floating-point data.
The result of providing a value that is not a floating-point
number (such as infinity or NaN) to such a command is
unspecified, but must not lead to GL interruption or termination.
Providing a denormalized number or negative zero to GL must yield
predictable results.
Changes to Chapter 3 of the OpenGL ES 2.0.25 Specification (Rasterization)
Add to Table 3.2, p. 62:
type Parameter Corresponding Special
Token Name GL Data Type Interpretation
------------------------------- ------------- --------------
UNSIGNED_INT_10F_11F_11F_REV_NV uint Yes
Add to Table 3.4, p. 63:
Format Type Bytes per Pixel
--------- ------------------------------- ---------------
RGB UNSIGNED_INT_10F_11F_11F_REV_NV 4
Add to Table 3.5, p. 64:
type Parameter GL Data Number of Matching
Token Name Type Components Pixel Formats
------------------------------- ------- ---------- --------------
UNSIGNED_INT_10F_11F_11F_REV_NV uint 3 RGB
Add the following to section 3.6.2 Transfor of Pixel Rectangles,
subsection Unpacking
UNSIGNED_INT_10F_11F_11F_REV_NV:
31 30 ... 23 22 21 20 ... 12 11 10 9 ... 1 0
+---------------+---------------+---------------+
| 3rd | 2nd | 1st |
+---------------+---------------+---------------+
Changes to Chapter 4 of the OpenGL ES 2.0.25 Specification
(Per-Fragment Operations and the Framebuffer)
Add the following to the end of Section 4.3, subsection
"Final Color Conversion"
If an implementation allows calling ReadPixels with a of
UNSIGNED_INT_10F_11F_11F_REV_NV and format of RGB, the conversion
is done as follows: The returned data are packed into a series of
GL uint values. The red, green, and blue components are converted
to unsigned 11-bit floating-point, unsigned 11-bit floating-point,
and unsigned 10-bit floating point as described in section
2.1.A and 2.1.B. The resulting red 11 bits, green 11 bits, and blue
10 bits are then packed as the 1st, 2nd, and 3rd components of the
UNSIGNED_INT_10F_11F_11F_REV_NV format as shown in Section 3.6.
Add to Table 4.4, p. 106:
type Parameter Component
Token Name GL Data Type Conversion Formula
-------------- ------------- ------------------
UNSIGNED_INT_10F_11F_11F_REV_NV uint c = f
(modify "Final Conversion", p. 106):
If type is not FLOAT, HALF_FLOAT_OES or UNSIGNED_INT_10F_11F_11F_REV_NV,
each component is first clamped to [0,1]. Then the appropriate conversion...
Add to Table 4.5, p. 117:
Sized Renderable R G B A D S
Internal Format Type bits bits bits bits bits bits
--------------- ---------------- ---- ---- ---- ---- ---- ----
R11F_G11F_B10F_NV color-renderable f11 f11 f10
Errors
Relaxation of INVALID_ENUM errors
---------------------------------
RenderbufferStorage and RenderBufferStorageMultisampleNV accept
the new R11F_G11F_B10F_EXT token for .
ReadPixels, TexImage2D, TexSubImage2D, TexImage3DNV and
TexSubImage3DNV accept the new UNSIGNED_INT_10F_11F_11F_REV_EXT
token for .
New errors
----------
INVALID_OPERATION is generated by ReadPixels, TexImage2D,
TexSubImage2D, TexImage3DNV and TexSubImage3DNV if is
UNSIGNED_INT_10F_11F_11F_REV_EXT and is not RGB.
Dependencies on OES_texture_half_float
If OES_texture_half_float is not supported, modify fifth paragraph
of 3.7.1 Texture Image Specification, p. 67:
"The selected groups are processed as described in section 3.6.2, stopping
after final expansion to RGBA. If the internal format of the texture is
fixed-point, components are clamped to [0,1]. Otherwise, values are not
modified."
Modify first sentence of "Unpacking", p. 62:
"Data are taken from client memory as a sequence of one of the GL data
types listed in Table 3.2. These elements are..."
Additionally, ignore all references to RGBA16F_EXT, RGB16F_EXT,
RG16F_EXT, R16F_EXT, HALF_FLOAT_OES and half.
Dependencies on EXT_color_buffer_half_float
If EXT_color_buffer_half_float is not supported, do not consider
R11F_G11F_B10F_NV color-renderable. Remove all changes and additions
to Chapter 4 of the OpenGL ES 2.0 Specification.
Dependencies on NV_packed_float_linear
If NV_packed_float_linear is not supported, using LINEAR
magnification filter and LINEAR, NEAREST_MIPMAP_LINEAR,
LINEAR_MIPMAP_NEAREST and LINEAR_MIPMAP_NEAREST minification
filters will cause packed float textures to be considered
incomplete.
Dependencies on NV_framebuffer_multisample
If NV_framebuffer_multisample is missing, remove all refernences to
RenderBufferStorageMultisampleNV.
Dependencies on NV_texture_array
If NV_texture_array is not supported, remove all references to
TexImage3DNV and TexSubImage3DNV.
Dependencies on EXT_texture_storage
If EXT_texture_storage is not supported, remove all references to
TexStorage2DEXT and TexStorage3DEXT.
Issues
1) Are the new formats allowed in window surface and pbuffer managed
by EGL?
No. Let's focus on framebuffer objects.
See EXT_packed_float for other relevant issues.
Revision History
#3 - 05.11.2012 (Mathias Heyer)
- Remove FRAMEBUFFER_ATTACHMENT_RGBA_SIGNED_COMPONENTS_NV, as its
neither in desktop GL nor ES3
#2 - 26.09.2012 (Mathias Heyer)
- Make FRAMEBUFFER_ATTACHMENT_RGBA_SIGNED_COMPONENTS_NV a property of
framebuffer attachments, adjust the table entries for ES2.0
- add interactions with various other ES2.0 extensions
#1 - 03.10.2008
First draft written based on EXT_packed_float.