> ## Name

> gp4fp - OpenGL fragment profile for NVIDIA GeForce 8/9/100/200/300 Series, OpenGL 3.x Quadro

> ## Synopsis

>       gp4fp

> ## Description

> This OpenGL profile corresponds to the per-fragment functionality introduced by NVIDIA's 4th generation of assembly instruction sets.

> The compiler output for this profile conforms to the assembly format defined by NV_gpu_program4 and ARB_fragment_program.

> Note that the NV_gpu_program4 extension has its fragment domain-specific aspects documented in the NV_fragment_program4 specification.

> Data-dependent loops and branching are allowed.

> Relative indexing of uniform arrays is supported.

> Parameter buffer objects (also known as "constant buffers" in DirectX 10 or "bindable uniform" in GLSL's EXT_bindable_uniform extension) provide a way to source uniform values from OpenGL buffer objects.

> Texture accesses include support for texture arrays (see the EXT_texture_array OpenGL extension for more details) and texture buffer objects (see the EXT_texture_buffer_object extension for details). Texture results can be either conventional floating-point vectors or integer vectors (see the EXT_texture_integer extension for details).

> If the system supports the NV_explicit_multisample OpenGL extension, renderbuffers can be bound as textures, which allows texture access to individual samples stored in multi-sample renderbuffer.

> ## 3D Api Dependencies

> Requires OpenGL support for the NV_gpu_program4 extension. This extension was introduced by the GeForce 8800 and other G8x-based GPUs. Renderbuffer sampler access requires NV_explicit_multisample extension.

> ## Opengl Extension Specifications

> Programmability:

>      http://www.opengl.org/registry/specs/NV/gpu_program4.txt

>      http://www.opengl.org/registry/specs/NV/fragment_program4.txt

> New texture samplers:

>      http://www.opengl.org/registry/specs/EXT/texture_array.txt

>      http://www.opengl.org/registry/specs/EXT/texture_buffer_object.txt

> New integer texture formats:

>      http://www.opengl.org/registry/specs/EXT/texture_integer.txt

> Draw buffers:

>      http://www.opengl.org/registry/specs/ARB/draw_buffers.txt

>      http://www.opengl.org/registry/specs/ATI/draw_buffers.txt

> Optional renderbuffer textures:

>      http://www.opengl.org/registry/specs/NV/explicit_multisample.txt

> ## Profile Options

> ## Fragment Domain-Specific Gp4 Options

> ARB_draw_buffers=val
> ATI_draw_buffers=val
>   Indicates that the ARB_draw_buffers or ATI_draw_buffers OpenGL extension is supported and what the extension's implementation dependent value of GL_MAX_DRAW_BUFFERS_ARB or GL_MAX_DRAW_BUFFERS_ATI is.
>   When specified, the compiler generates the "OPTION ARB_draw_buffers;" or "OPTION ATI_draw_buffers;" in the compiled code to enable output to multiple draw buffers. Output to multiple draw buffers is done by specifying output parameters with the COLOR1, COLOR2, etc. semantics.
>   GPUs that support these extensions typically support up to 4 buffers.
>   These options are useful in the rare situation you want to control the specific OPTION name used. For example, Apple drivers support the ARB_draw_buffers extension but not the ATI_draw_buffers extension.
>   The CgGL runtime routine cgGLSetOptimalOptions will automatically add the appropriate option based on querying the current OpenGL context's extension support (prefering the ARB extension) and specify the proper limit.

> ## Data Types

> ## Samplers

> This profile has additional samplers for texture arrays (1D and 2D) and texture buffers.

> Standard OpenGL textures formats (GL_RGBA8, etc.) return floating-point sampled results, but new signed and unsigned integer texture formats require samplers the return signed and unsigned integer vectors respectively. Sampler variants for fetching signed and unsigned integer vectors are prefixed by i and u respectively. Your application is required to make sure the bound textures have the appropriate texture format. So a 3D texture specified with the GL_RGBA32UI_EXT internal format (see the EXT_texture_integer OpenGL extension) must be used with a usampler3D sampler. Otherwise, texture sampling returns undefined results.

> sampler1D
>   1D texture unit corresponding to OpenGL's GL_TEXTURE_1D target. Sampling returns float vectors.
> isampler1D
>   1D texture unit corresponding to OpenGL's GL_TEXTURE_1D target. Sampling returns int vectors.
> usampler1D
>   1D texture unit corresponding to OpenGL's GL_TEXTURE_1D target. Sampling returns unsigned int vectors.
> sampler1DARRAY
>   1D array texture unit corresponding to OpenGL's GL_TEXTURE_1D_ARRAY_EXT target provided by the EXT_texture_array extension. Sampling returns float vectors.
> isampler1DARRAY
>   1D array texture unit corresponding to OpenGL's GL_TEXTURE_1D_ARRAY_EXT target provided by the EXT_texture_array extension. Sampling returns int vectors.
> usampler1DARRAY
>   1D array texture unit corresponding to OpenGL's GL_TEXTURE_1D_ARRAY_EXT target provided by the EXT_texture_array extension. Sampling returns unsigned int vectors.
> sampler2D
>   2D texture unit corresponding to OpenGL's GL_TEXTURE_2D target. Sampling returns float vectors.
> isampler2D
>   2D texture unit corresponding to OpenGL's GL_TEXTURE_2D target. Sampling returns int vectors.
> usampler2D
>   2D texture unit corresponding to OpenGL's GL_TEXTURE_2D target. Sampling returns unsigned int vectors.
> sampler2DARRAY
>   2D array texture unit corresponding to OpenGL's GL_TEXTURE_2D_ARRAY_EXT target provided by the EXT_texture_array extension. Sampling returns float vectors.
> isampler2DARRAY
>   2D array texture unit corresponding to OpenGL's GL_TEXTURE_2D_ARRAY_EXT target provided by the EXT_texture_array extension. Sampling returns int vectors.
> usampler2DARRAY
>   2D array texture unit corresponding to OpenGL's GL_TEXTURE_2D_ARRAY_EXT target provided by the EXT_texture_array extension. Sampling returns unsigned int vectors.
> sampler3D
>   3D texture unit corresponding to OpenGL's GL_TEXTURE_3D target. Sampling returns float vectors.
> isampler3D
>   3D texture unit corresponding to OpenGL's GL_TEXTURE_3D target. Sampling returns int vectors.
> usampler3D
>   3D texture unit corresponding to OpenGL's GL_TEXTURE_3D target. Sampling returns unsigned int vectors.
> samplerCUBE
>   Cube map texture unit corresponding to OpenGL's GL_TEXTURE_CUBE_MAP target. Sampling returns float vectors.
> isamplerCUBE
>   Cube map texture unit corresponding to OpenGL's GL_TEXTURE_CUBE_MAP target. Sampling returns int vectors.
> usamplerCUBE
>   Cube map texture unit corresponding to OpenGL's GL_TEXTURE_CUBE_MAP target. Sampling returns unsigned int vectors.
> samplerRECT
>   Rectangle texture unit corresponding to OpenGL's GL_TEXTURE_RECTANGLE_ARB target. Sampling returns float vectors.
> isamplerRECT
>   Rectangle texture unit corresponding to OpenGL's GL_TEXTURE_RECTANGLE_ARB target. Sampling returns int vectors.
> isamplerRECT
>   Rectangle texture unit corresponding to OpenGL's GL_TEXTURE_RECTANGLE_ARB target. Sampling returns unsigned int vectors.
> samplerBUF
>   Buffer texture unit corresponding to OpenGL's GL_TEXTURE_BUFFER_EXT target provided by the EXT_texture_buffer_object extension. Sampling returns float vectors.
> isamplerBUF
>   Buffer texture unit corresponding to OpenGL's GL_TEXTURE_BUFFER_EXT target provided by the EXT_texture_buffer_object extension. Sampling returns int vectors.
> usamplerBUF
>   Buffer texture unit corresponding to OpenGL's GL_TEXTURE_BUFFER_EXT target provided by the EXT_texture_buffer_object extension. Sampling returns unsigned int vectors.
> samplerRBUF
>   Renderbuffer texture unit corresponding to OpenGL's GL_TEXTURE_RENDERBUFFER_NV target provided by the NV_explicit_multisample extension. Sampling returns float vectors.
> isamplerRBUF
>   Renderbuffer texture unit corresponding to OpenGL's GL_TEXTURE_RENDERBUFFER_NV target provided by the NV_explicit_multisample extension. Sampling returns int vectors.
> usamplerRBUF
>   Renderbuffer texture unit corresponding to OpenGL's GL_TEXTURE_RENDERBUFFER_NV target provided by the NV_explicit_multisample extension. Sampling returns unsigned int vectors.

> ## Floating-Point

> float
>   32-bit IEEE floating-point
> half
>   32-bit IEEE floating-point
> double
>   32-bit IEEE floating-point
> fixed
>   Floating-point restricted to [-2,2) range.

> ## Integer

> This profile supports "true" integer data types. Shifting and bitwise operators are supported for integer data types.

> int
>   32-bit signed integer
> unsigned int
>   32-bit unsigned integer
> short
>   16-bit signed integer
> unsigned short
>   16-bit unsigned integer
> char
>   8-bit signed integer
> unsigned char
>   8-bit unsigned integer

> ## Semantics

> ## Varying Input Semantics

> ## Interpolated Input Semantics

> The varying input semantics in the gp4fp profile correspond to the respectively named varying output semantics of the gp4vp profile (or gp4gp if a geometry shader is present).

>     Binding Semantics Name           Corresponding Data

>     COLOR                            Input primary color
>     COLOR0
>     COL
>     COL0

>     COLOR1                           Input secondary color
>     COL1

>     WPOS                             Window position (with lower-left origin)

>     TEX0                             Input texture coordinate sets 0
>     TEXCOORD0

>     TEX1                             Input texture coordinate sets 1
>     TEXCOORD1

>     TEX2                             Input texture coordinate sets 2
>     TEXCOORD2

>     TEX3                             Input texture coordinate sets 3
>     TEXCOORD3

>     TEX4                             Input texture coordinate sets 4
>     TEXCOORD4

>     TEX5                             Input texture coordinate sets 5
>     TEXCOORD5

>     TEX6                             Input texture coordinate sets 6
>     TEXCOORD6

>     TEX7                             Input texture coordinate sets 7
>     TEXCOORD7

>     FOGP                             Input fog color (XYZ) and factor (W)
>     FOG

> ## Interpolation Semantic Modifiers

> A number of interpolation semantic modifiers control how interpolation happens for the interpolated input semantics above. These modifiers are suffixed to the semantic name with a "." (period) seperator. Without a modifier, perspective-correct interpolation applies.

>     Semantic Modifier Name           Meaning

>     CENTROID                         Interpolate at the centroid of the covered samples
>                                      (only applies when rendering to multisampled surface)

>     FLAT                             Flat shading using provoking vertex's value

>     NOPERSPECTIVE                    Interpolate without perspective correction

> Examples:

>     float4 a : TEXCOORD0
>     float4 b : TEXCOORD1.CENTROID
>     float4 c : TEXCOORD2.FLAT
>     float4 d : TEXCOORD3.NOPERSPECTIVE

> ## Per-Primitive Input Semantics

>     FACE                             Polygon facing.
>                                      +1 for front-facing polygon or line or point
>                                      -1 for back-facing polygon

>     PRIMITIVEID                      Primitive ID (int)

> If a geometry program is active, parameters given the PRIMITIVEID semantic obtained their integer value from the primitive ID value emitted by the geometry program for the provoking vertex. If no geometry program is active, the value is the number of primitives processed by the rasterizer since the last time glBegin was called (directly or indirectly via vertex array functions). The first primitive generated after a glBegin is numbered zero, and the primitive ID counter is incremented after every individual point, line, or polygon primitive is processed. For polygons drawn in point or line mode, the primitive ID counter is incremented only once, even though multiple points or lines may be drawn. For QUADS and QUAD_STRIP primitives that are decomposed into triangles, the primitive ID is incremented after each complete quad is processed. For POLYGON primitives, the primitive ID counter is zero. The primitive ID is zero for fragments generated by DrawPixels or Bitmap. Restarting a primitive topology using the primitive restart index has no effect on the primitive ID counter.

> ## Uniform Input Semantics

> ## Buffer Semantics

> gp4 profiles can specify that uniforms be specified to reside within binable buffers.

> Example of automatic, compiler-determined specification of a uniform's location within a buffer:

>     uniform float2 location   : BUFFER[3];  // compiler positions within buffer 3
>     uniform float4 brickColor : BUFFER[3];  // compiler positions within buffer 3

> Example of absolute byte offset specification of a uniform's locaiton within a buffer:

>       uniform float4 mustBeHere : BUFFER[7][20];  // locate 20 bytes into buffer 7

> ## Constant Register Semantics

>     C0-C255           Constant register [0..255].
>                       The aliases c0-c255 (lowercase) are also accepted.

> If used with a variable that requires more than one constant register (e.g. a matrix), the semantic specifies the first register that is used.

> Example:

>       uniform float4 array[20] : C14;  // uses c14 through c33

> ## Texture Unit Semantics

>       TEXUNIT0-TEXUNIT31  Texture image unit

> Example:

>       uniform sampler2DARRAY texArray : TEXUNIT7;

> ## Output Semantics

>     COLOR                            Output color (float4 or int4)
>     COL

>     COLOR0-COLOR7                    Output color (float4 or int4) for draw buffers 0 to 7
>     COL0-COL7

>     DEPTH                            Output depth (float)
>     DEPR

> ## Standard Library Issues

> ## Raw Cast From Floating-Point To Integer Functions

> It is possible to convert the raw bit patterns of IEEE single-precision floating-point to 32-bit unsigned integer.

> floatToRawIntBits, floatToIntBits, intBitsToFloat

> ## Texture Array Functions

> New sampler data types for texture arrays and texture buffers lead to new standard library routines to access these samplers.

> New standard library functions are used to access 1D texture array samplers (sampler1DARRAY).

> tex1DARRAY, tex1DARRAYbias, tex1DARRAYcmpbias, tex1DARRAYlod, tex1DARRAYcmplod, tex1DARRAYproj

> The dimensions of a texture array level can be determined.

> tex1DARRAYsize

> New standard library functions are used to access 2D texture array samplers (sampler2DARRAY).

> tex2DARRAY, tex2DARRAYbias, tex2DARRAYlod, tex2DARRAYproj

> The dimensions of a texture array level can be determined.

> tex2DARRAYsize

> ## See Also

> gp4, gp4vp, gp4gp, texBUF, texBUFsize, texRBUF, texRBUFsize, floatToRawIntBits, floatToIntBits, intBitsToFloat, tex1DARRAY, tex1DARRAYbias, tex1DARRAYcmpbias, tex1DARRAYlod, tex1DARRAYcmplod, tex1DARRAYproj, tex1DARRAYsize, tex2DARRAY, tex2DARRAYbias, tex2DARRAYlod, tex2DARRAYproj, tex2DARRAYsize