skia / external / github.com / KhronosGroup / OpenGL-Registry / eae1d6dde1e283f6fdf803274a2484007e592599 / . / extensions / NV / NV_packed_float.txt

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 <internalformat> parameter of RenderbufferStorage | |

and RenderBufferStorageMultisampleNV, TexStorage2DEXT and | |

TexStorage3DEXT: | |

R11F_G11F_B10F_NV 0x8C3A | |

Accepted by the <type> 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 <type> 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 <internalformat>. | |

ReadPixels, TexImage2D, TexSubImage2D, TexImage3DNV and | |

TexSubImage3DNV accept the new UNSIGNED_INT_10F_11F_11F_REV_EXT | |

token for <type>. | |

New errors | |

---------- | |

INVALID_OPERATION is generated by ReadPixels, TexImage2D, | |

TexSubImage2D, TexImage3DNV and TexSubImage3DNV if <type> is | |

UNSIGNED_INT_10F_11F_11F_REV_EXT and <format> 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. |