| Name |
| |
| EXT_texture_snorm |
| |
| Name Strings |
| |
| GL_EXT_texture_snorm |
| |
| Contributors |
| |
| Bill Licea-Kane, AMD |
| Jon Leech, Khronos |
| Mais Alnasser, AMD |
| Nick Haemel, AMD |
| |
| Contact |
| |
| Bill Licea-Kane, (bill.licea-kane 'at' amd.com) |
| |
| Status |
| |
| Draft for OpenGL 3.1 |
| |
| Version |
| |
| Last Modified Date: 2009-07-10 |
| Revision: 5 |
| |
| Number |
| |
| 365 |
| |
| Dependencies |
| |
| OpenGL 3.0 is required. |
| |
| This extension is written against the OpenGL 3.0 specification. |
| |
| Overview |
| |
| Fixed-point textures in unextended OpenGL have integer components, |
| but those values are taken to represent floating-point values in |
| the range [0.0,1.0]. These integer components are considered |
| "unsigned normalized" integers. When such a texture is accessed by |
| a shader or by fixed-function fragment processing, floating-point |
| values are returned in the range [0.0,1.0]. |
| |
| This extension provides a set of new "signed normalized" integer |
| texture formats. These are taken to represent a floating-point |
| value in the range [-1.0,1.0] with an exact 0.0. |
| |
| New Procedures and Functions |
| |
| None |
| |
| New Tokens |
| |
| |
| Accepted by the <internalFormat> parameter of TexImage1D, |
| TexImage2D, and TexImage3D: |
| |
| base internal formats |
| RED_SNORM 0x8F90 |
| RG_SNORM 0x8F91 |
| RGB_SNORM 0x8F92 |
| RGBA_SNORM 0x8F93 |
| ALPHA_SNORM 0x9010 |
| LUMINANCE_SNORM 0x9011 |
| LUMINANCE_ALPHA_SNORM 0x9012 |
| INTENSITY_SNORM 0x9013 |
| |
| |
| sized internal formats |
| R8_SNORM 0x8F94 |
| RG8_SNORM 0x8F95 |
| RGB8_SNORM 0x8F96 |
| RGBA8_SNORM 0x8F97 |
| ALPHA8_SNORM 0x9014 |
| LUMINANCE8_SNORM 0x9015 |
| LUMINANCE8_ALPHA8_SNORM 0x9016 |
| INTENSITY8_SNORM 0x9017 |
| |
| R16_SNORM 0x8F98 |
| RG16_SNORM 0x8F99 |
| RGB16_SNORM 0x8F9A |
| RGBA16_SNORM 0x8F9B |
| ALPHA16_SNORM 0x9018 |
| LUMINANCE16_SNORM 0x9019 |
| LUMINANCE16_ALPHA16_SNORM 0x901A |
| INTENSITY16_SNORM 0x901B |
| |
| Returned by GetTexLevelParmeter |
| |
| SIGNED_NORMALIZED 0x8F9C |
| |
| Additions to Chapter 2 of the OpenGL 3.0 Specification (OpenGL Operation) |
| |
| Modify Section 2.19 Colors and Coloring, p. 74 |
| |
| Replace Table 2.10: Component Conversions: |
| |
| GL Type of <c> Conversion to internal floating-point |
| unsigned normalized, signed normalized |
| -------------- ------------------------------------- |
| ubyte <c>/(2^8-1), <c>/(2^7-1) |
| byte (2<c>+1)/(2^8-1), max ( <c>/(2^7-1), -1.0 ) |
| ushort <c>/(2^16-1), <c>/(2^15-1) |
| short (2<c>+1)/(2^16-1), max ( <c>/(2^15-1), -1.0 ) |
| uint <c>/(2^32-1), <c>/(2^31-1) |
| int (2<c>+1)/(2^32-1), max ( <c>/(2^31-1), -1.0 ) |
| half <c> |
| float <c> |
| double <c> |
| |
| |
| Additions to Chapter 3 of the OpenGL 2.0 Specification (Rasterization) |
| |
| Modify Section 3.9 (Texturing), p. 175 |
| |
| Modify second paragraph: |
| |
| The internal data type of a texture may be signed normalized |
| fixed-point, unsigned normalized fixed-point, floating-point, |
| signed integer or unsigned integer, depending on the internal |
| format of the texture. The correspondence between internal format |
| and the internal data type is given in tables 3.16-3.18. |
| Fixed-point and floating-point textures return a floating-point |
| value and integer textures return signed or unsigned integer |
| values. When a fragment shader is active, the shader is responsible |
| for interpreting the result of a texture lookup as the correct data |
| type, otherwise the result is undefined. When not using a fragment |
| shader, unsigned floating-point texture values are assumed, and the |
| results of using either signed normalized fixed-point or integer |
| textures in this case are undefined. |
| |
| Modify Section 3.9.1 (Texture Image Specification), p. 176 |
| |
| (modify last paragraph beginning p. 176): |
| |
| The selected groups are processed exactly as for DrawPixels, |
| stopping just before final conversion. If the <internalformat> of |
| the texture is integer, the components are clamped to the |
| representable range of the internal format: for signed formats, |
| this is [-2^(n-1), 2^(n-1)-1] where n is the number of bits per |
| component; for unsigned formats, the range is [0, 2^n-1]. For R, G, |
| B, and A, if the <internalformat> of the texture is fixed-point, |
| the components are clamped to the representable range of the |
| internal format: for signed normalized formats, this is [-1.0, |
| 1.0]; for unsigned normalized formats, this is [0.0, 1.0]. |
| Otherwise, the components are not modified. |
| |
| |
| (add the following required Color formats (texture-only), p. 179) |
| |
| - R16_SNORM, RG16_SNORM, RGB16_SNORM, RGBA16_SNORM, |
| R8_SNORM, RG8_SNORM, RGB8_SNORM, RGBA8_SNORM |
| |
| (add the following to table 3.16, beginning p. 181) |
| |
| Sized Base R G B A L I |
| Internal Format Internal Format bits bits bits bits bits bits |
| ----------------------- --------------------- ---- ---- ---- ---- ---- ---- |
| R8_SNORM R_SNORM 8 |
| RG8_SNORM RG_SNORM 8 8 |
| RGB8_SNORM RGB_SNORM 8 8 8 |
| RGBA8_SNORM RGBA_SNORM 8 8 8 8 |
| ALPHA8_SNORM ALPHA8_SNORM 8 |
| LUMINANCE8_SNORM LUMINANCE8_SNORM 8 |
| LUMINANCE8_ALPHA8_SNORM LUMINANCE8_ALPHA8_SNORM 8 8 |
| INTENSITY8_SNORM INTENSITY8_SNORM 8 |
| |
| R16_SNORM R_SNORM 16 |
| RG16_SNORM RG_SNORM 16 16 |
| RGB16_SNORM RGB_SNORm 16 16 16 |
| RGBA16_SNORM RGBA_SNORM 16 16 16 16 |
| ALPHA8_SNORM ALPHA8_SNORM 16 |
| LUMINANCE16_SNORM LUMINANCE16_SNORM 16 |
| LUMINANCE16_ALPHA16_SNORM LUMINANCE16_ALPHA16_SNORM 16 16 |
| INTENSITY16_SNORM INTENSITY16_SNORM 16 |
| |
| Table 3.16: Correspondence of sized internal formats to base |
| internal formats, internal data type and desired component |
| resolutions for each sized internal format. The component |
| resolution prefix indicates the internal data type: <f> is floating |
| point, <i> is signed integer, <ui> is unsigned integer, and no |
| prefix is signed or unsigned normalized fixed-point. |
| |
| Modify Section 3.12.2 Shader Execution |
| |
| (modify Shader Outputs paragraph, p. 234) |
| |
| XXXXX - Is this section broken? |
| |
| The OpenGL Shading Language specification describes the values that |
| may be output by a fragment shader. These outputs are split into |
| two categories, user-defined varying out variables and built-in |
| variables. The built-in variables are gl_FragColor, gl_FragData[n], |
| and gl_FragDepth. If fragment color clamping is enabled and the |
| color buffer has a unsigned normalized fixed-point format, signed |
| normalized fixed-point format, or floating-point format, the final |
| fragment color, fragment data, or varying out variable values |
| written by a fragment shader are clamped to the range [0, 1] and |
| are optionally converted to normalized fixed-point as described in |
| section 2.19.9. |
| |
| |
| Additions to Chapter 4 of the OpenGL 2.0 Specification (Per-Fragment |
| Operations and the Frame Buffer) |
| |
| Modify Chapter 4 Introduction, (p. 239) |
| |
| (modify second paragraph, p. 239) |
| |
| Each pixel in a color buffer consists of either a single unsigned |
| integer color index or up to four color components. The four color |
| components are named R, G, B, and A, in that order; color buffers |
| are not required to have all four color components. R, G, B, and A |
| components may be represented as unsigned normalized fixed-point, |
| signed normalized fixed-point, floating-point, signed integer, or |
| unsigned integer values; all components must have the same |
| representation.... |
| |
| |
| XXXX - Clear section needs changing? |
| |
| Additions to Chapter 6 of the OpenGL 2.0 Specification (State and |
| State Requests) |
| |
| Modify Section 6.1.3 (Enumerated Queries), p. 318 |
| |
| (Modify beginning paragraph starting on p. 318) |
| |
| For texture images with uncompressed internal formats, queries of |
| value of TEXTURE_RED_TYPE, TEXTURE_GREEN_TYPE, TEXTURE_BLUE_TYPE, |
| TEXTURE_ALPHA_TYPE, TEXTURE_LUMINANCE_TYPE, TEXTURE_DEPTH_TYPE, |
| and TEXTURE_INTENSITY_TYPE return the data type used to store the |
| component. Types NONE, UNSIGNED_NORMALIZED, SIGNED_NORMALIZED, |
| FLOAT, INT,and UNSIGNED_INT respectively indicate missing, |
| unsigned normalized integer, signed normalized integer, |
| floating-point, signed unnormalized integer, and unsigned |
| unnormalized integer components.... |
| |
| GLX Protocol |
| |
| TBD |
| |
| Errors |
| |
| |
| Issues |
| |
| 1 - Should the internalformat enums contain an underscore? |
| |
| RESOLVED: Yes. _SNORM internal format modifier is nearly |
| unreadable without it. (Especially for sized formats.) |
| |
| 2 - What are the required signed normalized formats? |
| |
| RESOLVED: We require 8 and 16 bit R, RG, RGB, RGBA texturing. |
| It follows that these are filterable. |
| |
| We are silent about requiring R, RG, RBA and RGBA rendering. |
| This is an implementation choice. Note that some "OpenGL 3.0 |
| target hardware" (multiple implementations) have blending |
| limitations with signed normalized color formats. We are |
| restricted to "OpenGL 3.0 target hardware" for 3.1 candidates. |
| |
| 3 - Shader outputs broken? |
| |
| Final color processing (Chapter 2), Clamping (Several) and |
| conversion to framebuffer are intertwined at several places |
| in the spec now. Some of the statements in this section |
| appear to conflict with statements in other sections. |
| |
| 4 - Clear? |
| |
| Do we need to be able to clear a signed normalized fixed-point |
| buffer to the full range of [-1.0,1.0]? If so, any changes |
| needed here? |
| |
| 5 - Should this "extension spec" be updated to accurately reflect the |
| final 3.0 -> 3.1 deltas? |
| |
| Resolved - Ideally, but not now. Jon made many major structural |
| changes to the core spec in 3.0 -> 3.1. See the core 3.1 spec |
| with differences tracked for details. |
| |
| |
| Revision History: |
| |
| Date: 2009-07-10 |
| Revision: 5 (Jon Leech) |
| Assign extension number, minor formatting cleanups for registry. |
| |
| Date: 2009-04-29 |
| Revision: 4 (gsellers) |
| Add contributors. |
| |
| Date: 2009-04-22 |
| Revision: 3 (wwlk) |
| Add token values, for R,RG,RGB, RGBA and for "legacy" formats |
| alpha, luminace, luminance alpha and intensity. |
| Added unsigned conversions. |
| Fixed typos in enums: |
| LUMINANCE_ALPHA8_SNORM -> LUMINANCE8_ALPHA8_SNORM |
| LUMINANCE_ALPHA16_SNORM -> LUMINANCE16_ALPHA16_SNORM |
| |
| Date: 2009-03-17 |
| Revision: 2 (wwlk) |
| Fixed enum inconsistencies |
| |
| Date: 2008-10-30 |
| Revision: 1 (wwlk) |
| Initial version |
| |
| |
| |
