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Diffstat (limited to 'src/mesa/shader/slang_fragment_builtin.gc')
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diff --git a/src/mesa/shader/slang_fragment_builtin.gc b/src/mesa/shader/slang_fragment_builtin.gc new file mode 100755 index 00000000000..6ccf0e7c0fc --- /dev/null +++ b/src/mesa/shader/slang_fragment_builtin.gc @@ -0,0 +1,354 @@ +
+//
+// TODO:
+// - implement texture1D, texture2D, texture3D, textureCube,
+// - implement shadow1D, shadow2D,
+// - implement dFdx, dFdy,
+//
+
+//
+// From Shader Spec, ver. 1.051
+//
+// The output of the fragment shader goes on to be processed by the fixed function operations at
+// the back end of the OpenGL pipeline. Fragment shaders interface with the back end of the OpenGL
+// pipeline using the built-in variables gl_FragColor and gl_FragDepth, or by executing the discard
+// keyword.
+//
+// These variables may be written more than once within a fragment shader. If so, the last value
+// assigned is the one used in the subsequent fixed function pipeline. The values written to these
+// variables may be read back after writing them. Reading from these variables before writing them
+// results in an undefined value. The fixed functionality computed depth for a fragment may be
+// obtained by reading gl_FragCoord.z, described below.
+//
+// Writing to gl_FragColor specifies the fragment color that will be used by the subsequent fixed
+// functionality pipeline. If subsequent fixed functionality consumes fragment color and an
+// execution of a fragment shader does not write a value to gl_FragColor then the fragment color
+// consumed is undefined.
+//
+// If the frame buffer is configured as a color index buffer then behavior is undefined when using
+// a fragment shader.
+//
+// Writing to gl_FragDepth will establish the depth value for the fragment being processed. If
+// depth buffering is enabled, and a shader does not write gl_FragDepth, then the fixed function
+// value for depth will be used as the fragment�s depth value. If a shader statically assigns
+// a value to gl_FragDepth, and there is an execution path through the shader that does not set
+// gl_FragDepth, then the value of the fragment�s depth may be undefined for some executions of
+// the shader. That is, if a shader statically writes gl_FragDepth, then it is responsible for
+// always writing it. There is also no guarantee that a shader can compute the same depth value
+// as the fixed function value; an implementation will provide invariant results within shaders
+// computing depth with the same source-level expression, but invariance is not provided between
+// shaders and fixed functionality.
+//
+// Writes to gl_FragColor and gl_FragDepth need not be clamped within a shader. The fixed
+// functionality pipeline following the fragment shader will clamp these values.
+//
+// If a shader executes the discard keyword, the fragment is discarded, and the values of
+// gl_FragDepth and gl_FragColor become irrelevant.
+//
+// The variable gl_FragCoord is available as a read-only variable from within fragment shaders
+// and it holds the window relative coordinates x, y, z, and 1/w values for the fragment. This
+// value is the result of the fixed functionality that interpolates primitives after vertex
+// processing to generate fragments. The z component is the depth value that would be used for
+// the fragment�s depth if a shader contained no writes to gl_FragDepth. This is useful for
+// invariance if a shader conditionally computes gl_FragDepth but otherwise wants the fixed
+// functionality fragment depth.
+//
+// The fragment shader has access to the read-only built-in variable gl_FrontFacing whose value
+// is true if the fragment belongs to a front-facing primitive. One use of this is to emulate
+// two-sided lighting by selecting one of two colors calculated by the vertex shader.
+//
+// The built-in variables that are accessible from a fragment shader are intrinsically given types
+// as follows:
+//
+
+vec4 gl_FragCoord;
+bool gl_FrontFacing;
+vec4 gl_FragColor;
+float gl_FragDepth;
+
+//
+// However, they do not behave like variables with no qualifier; their behavior is as described
+// above. These built-in variables have global scope.
+//
+
+//
+// Unlike user-defined varying variables, the built-in varying variables don�t have a strict
+// one-to-one correspondence between the vertex language and the fragment language. Two sets are
+// provided, one for each language. Their relationship is described below.
+//
+// The following varying variables are available to read from in a fragment shader. The gl_Color
+// and gl_SecondaryColor names are the same names as attributes passed to the vertex shader.
+// However, there is no name conflict, because attributes are visible only in vertex shaders
+// and the following are only visible in a fragment shader.
+//
+
+varying vec4 gl_Color;
+varying vec4 gl_SecondaryColor;
+varying vec4 gl_TexCoord[]; // at most will be gl_MaxTextureCoordsARB
+varying float gl_FogFragCoord;
+
+//
+// The values in gl_Color and gl_SecondaryColor will be derived automatically by the system from
+// gl_FrontColor, gl_BackColor, gl_FrontSecondaryColor, and gl_BackSecondaryColor based on which
+// face is visible. If fixed functionality is used for vertex processing, then gl_FogFragCoord will
+// either be the z-coordinate of the fragment in eye space, or the interpolation of the fog
+// coordinate, as described in section 3.10 of the OpenGL 1.4 Specification. The gl_TexCoord[]
+// values are the interpolated gl_TexCoord[] values from a vertex shader or the texture coordinates
+// of any fixed pipeline based vertex functionality.
+//
+// Indices to the fragment shader gl_TexCoord array are as described above in the vertex shader
+// text.
+//
+
+//
+// The OpenGL Shading Language defines an assortment of built-in convenience functions for scalar
+// and vector operations. Many of these built-in functions can be used in more than one type
+// of shader, but some are intended to provide a direct mapping to hardware and so are available
+// only for a specific type of shader.
+//
+// The built-in functions basically fall into three categories:
+//
+// � They expose some necessary hardware functionality in a convenient way such as accessing
+// a texture map. There is no way in the language for these functions to be emulated by a shader.
+//
+// � They represent a trivial operation (clamp, mix, etc.) that is very simple for the user
+// to write, but they are very common and may have direct hardware support. It is a very hard
+// problem for the compiler to map expressions to complex assembler instructions.
+//
+// � They represent an operation graphics hardware is likely to accelerate at some point. The
+// trigonometry functions fall into this category.
+//
+// Many of the functions are similar to the same named ones in common C libraries, but they support
+// vector input as well as the more traditional scalar input.
+//
+// Applications should be encouraged to use the built-in functions rather than do the equivalent
+// computations in their own shader code since the built-in functions are assumed to be optimal
+// (e.g., perhaps supported directly in hardware).
+//
+// User code can replace built-in functions with their own if they choose, by simply re-declaring
+// and defining the same name and argument list.
+//
+
+//
+// Texture Lookup Functions
+//
+// Texture lookup functions are available to both vertex and fragment shaders. However, level
+// of detail is not computed by fixed functionality for vertex shaders, so there are some
+// differences in operation between vertex and fragment texture lookups. The functions in the table
+// below provide access to textures through samplers, as set up through the OpenGL API. Texture
+// properties such as size, pixel format, number of dimensions, filtering method, number of mip-map
+// levels, depth comparison, and so on are also defined by OpenGL API calls. Such properties are
+// taken into account as the texture is accessed via the built-in functions defined below.
+//
+// If a non-shadow texture call is made to a sampler whose texture has depth comparisons enabled,
+// then results are undefined. If a shadow texture call is made to a sampler whose texture does not
+// have depth comparisions enabled, the results are also undefined.
+//
+// In all functions below, the bias parameter is optional for fragment shaders. The bias parameter
+// is not accepted in a vertex shader. For a fragment shader, if bias is present, it is added to
+// the calculated level of detail prior to performing the texture access operation. If the bias
+// parameter is not provided, then the implementation automatically selects level of detail:
+// For a texture that is not mip-mapped, the texture is used directly. If it is mip-mapped and
+// running in a fragment shader, the LOD computed by the implementation is used to do the texture
+// lookup. If it is mip-mapped and running on the vertex shader, then the base texture is used.
+//
+// The built-ins suffixed with �Lod� are allowed only in a vertex shader. For the �Lod� functions,
+// lod is directly used as the level of detail.
+//
+
+//
+// Use the texture coordinate coord to do a texture lookup in the 1D texture currently bound
+// to sampler. For the projective (�Proj�) versions, the texture coordinate coord.s is divided by
+// the last component of coord.
+//
+// XXX
+vec4 texture1D (sampler1D sampler, float coord, float bias) {
+ return vec4 (0.0);
+}
+vec4 texture1DProj (sampler1D sampler, vec2 coord, float bias) {
+ return texture1D (sampler, coord.s / coord.t, bias);
+}
+vec4 texture1DProj (sampler1D sampler, vec4 coord, float bias) {
+ return texture1D (sampler, coord.s / coord.q, bias);
+}
+
+//
+// Use the texture coordinate coord to do a texture lookup in the 2D texture currently bound
+// to sampler. For the projective (�Proj�) versions, the texture coordinate (coord.s, coord.t) is
+// divided by the last component of coord. The third component of coord is ignored for the vec4
+// coord variant.
+//
+// XXX
+vec4 texture2D (sampler2D sampler, vec2 coord, float bias) {
+ return vec4 (0.0);
+}
+vec4 texture2DProj (sampler2D sampler, vec3 coord, float bias) {
+ return texture2D (sampler, vec2 (coord.s / coord.p, coord.t / coord.p), bias);
+}
+vec4 texture2DProj (sampler2D sampler, vec4 coord, float bias) {
+ return texture2D (sampler, vec2 (coord.s / coord.q, coord.s / coord.q), bias);
+}
+
+//
+// Use the texture coordinate coord to do a texture lookup in the 3D texture currently bound
+// to sampler. For the projective (�Proj�) versions, the texture coordinate is divided by coord.q.
+//
+// XXX
+vec4 texture3D (sampler3D sampler, vec3 coord, float bias) {
+ return vec4 (0.0);
+}
+vec4 texture3DProj (sampler3D sampler, vec4 coord, float bias) {
+ return texture3DProj (sampler, vec3 (coord.s / coord.q, coord.t / coord.q, coord.p / coord.q),
+ bias);
+}
+
+//
+// Use the texture coordinate coord to do a texture lookup in the cube map texture currently bound
+// to sampler. The direction of coord is used to select which face to do a 2-dimensional texture
+// lookup in, as described in section 3.8.6 in version 1.4 of the OpenGL specification.
+//
+// XXX
+vec4 textureCube (samplerCube sampler, vec3 coord, float bias) {
+ return vec4 (0.0);
+}
+
+//
+// Use texture coordinate coord to do a depth comparison lookup on the depth texture bound
+// to sampler, as described in section 3.8.14 of version 1.4 of the OpenGL specification. The 3rd
+// component of coord (coord.p) is used as the R value. The texture bound to sampler must be a
+// depth texture, or results are undefined. For the projective (�Proj�) version of each built-in,
+// the texture coordinate is divide by coord.q, giving a depth value R of coord.p/coord.q. The
+// second component of coord is ignored for the �1D� variants.
+//
+// XXX
+vec4 shadow1D (sampler1DShadow sampler, vec3 coord, float bias) {
+ return vec4 (0.0);
+}
+// XXX
+vec4 shadow2D (sampler2DShadow sampler, vec3 coord, float bias) {
+ return vec4 (0.0);
+}
+vec4 shadow1DProj (sampler1DShadow sampler, vec4 coord, float bias) {
+ return shadow1D (sampler, vec3 (coord.s / coord.q, 0.0, coord.p / coord.q), bias);
+}
+vec4 shadow2DProj (sampler2DShadow sampler, vec4 coord, float bias) {
+ return shadow2D (sampler, vec3 (coord.s / coord.q, coord.t / coord.q, coord.p / coord.q), bias);
+}
+
+//
+// Fragment processing functions are only available in shaders intended for use on the fragment
+// processor. Derivatives may be computationally expensive and/or numerically unstable. Therefore,
+// an OpenGL implementation may approximate the true derivatives by using a fast but not entirely
+// accurate derivative computation.
+//
+// The expected behavior of a derivative is specified using forward/backward differencing.
+//
+// Forward differencing:
+//
+// F(x+dx) - F(x) ~ dFdx(x) * dx 1a
+// dFdx(x) ~ (F(x+dx) - F(x)) / dx 1b
+//
+// Backward differencing:
+//
+// F(x-dx) - F(x) ~ -dFdx(x) * dx 2a
+// dFdx(x) ~ (F(x) - F(x-dx)) / dx 2b
+//
+// With single-sample rasterization, dx <= 1.0 in equations 1b and 2b. For multi-sample
+// rasterization, dx < 2.0 in equations 1b and 2b.
+//
+// dFdy is approximated similarly, with y replacing x.
+//
+// A GL implementation may use the above or other methods to perform the calculation, subject
+// to the following conditions:
+//
+// 1) The method may use piecewise linear approximations. Such linear approximations imply that
+// higher order derivatives, dFdx(dFdx(x)) and above, are undefined.
+//
+// 2) The method may assume that the function evaluated is continuous. Therefore derivatives within
+// the body of a non-uniform conditional are undefined.
+//
+// 3) The method may differ per fragment, subject to the constraint that the method may vary by
+// window coordinates, not screen coordinates. The invariance requirement described in section
+// 3.1 of the OpenGL 1.4 specification is relaxed for derivative calculations, because
+// the method may be a function of fragment location.
+//
+// Other properties that are desirable, but not required, are:
+//
+// 4) Functions should be evaluated within the interior of a primitive (interpolated, not
+// extrapolated).
+//
+// 5) Functions for dFdx should be evaluated while holding y constant. Functions for dFdy should
+// be evaluated while holding x constant. However, mixed higher order derivatives, like
+// dFdx(dFdy(y)) and dFdy(dFdx(x)) are undefined.
+//
+// In some implementations, varying degrees of derivative accuracy may be obtained by providing
+// GL hints (section 5.6 of the OpenGL 1.4 specification), allowing a user to make an image
+// quality versus speed tradeoff.
+//
+
+//
+// Returns the derivative in x using local differencing for the input argument p.
+//
+// XXX
+float dFdx (float p) {
+ return 0.0;
+}
+// XXX
+vec2 dFdx (vec2 p) {
+ return vec2 (0.0);
+}
+// XXX
+vec3 dFdx (vec3 p) {
+ return vec3 (0.0);
+}
+// XXX
+vec4 dFdx (vec4 p) {
+ return vec4 (0.0);
+}
+
+//
+// Returns the derivative in y using local differencing for the input argument p.
+//
+// These two functions are commonly used to estimate the filter width used to anti-alias procedural
+// textures.We are assuming that the expression is being evaluated in parallel on a SIMD array so
+// that at any given point in time the value of the function is known at the grid points
+// represented by the SIMD array. Local differencing between SIMD array elements can therefore
+// be used to derive dFdx, dFdy, etc.
+//
+// XXX
+float dFdy (float p) {
+ return 0.0;
+}
+// XXX
+vec2 dFdy (vec2 p) {
+ return vec2 (0.0);
+}
+// XXX
+vec3 dFdy (vec3 p) {
+ return vec3 (0.0);
+}
+// XXX
+vec4 dFdy (vec4 p) {
+ return vec4 (0.0);
+}
+
+//
+// Returns the sum of the absolute derivative in x and y using local differencing for the input
+// argument p, i.e.:
+//
+// return = abs (dFdx (p)) + abs (dFdy (p));
+//
+
+float fwidth (float p) {
+ return abs (dFdx (p)) + abs (dFdy (p));
+}
+vec2 fwidth (vec2 p) {
+ return abs (dFdx (p)) + abs (dFdy (p));
+}
+vec3 fwidth (vec3 p) {
+ return abs (dFdx (p)) + abs (dFdy (p));
+}
+vec4 fwidth (vec4 p) {
+ return abs (dFdx (p)) + abs (dFdy (p));
+}
+
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