XXX - Dead -- couldn't convince the ARB. Use fragment_lighting & XXX separate_specular_color instead. XXX - Not complete yet!!! Name SGIX_fragment_specular_lighting Name Strings GL_SGIX_fragment_specular_lighting Version $Date: 1998/07/06 19:51:38 $ $Revision: 1.2 $ Number ?? Dependencies OpenGL 1.1 is required. SGIX_color_range affects the definition of this extension. Overview This extension adds a new lighting stage to the OpenGL pipeline. This stage occurs during fragment processing after the texture environment has been applied and before fog has been applied. The extension provides a mechanism for computing a post-texture specular lighting term. This extension doesn't eliminate the specular term in vertex lighting, but can be used to augment it. This extension provides the state framework for a more general lighting model, but only includes the equation for computing the specular contribution. The more general version is described in SGIX_fragment_lighting. Ct Cf | |-------------------------------+ | | | ---------- | | | | | TexEnv | | | | | ---------- | | | ---------- | | Clamp | Nf Lf Hf Ff | ---------- | | | | | | ----------------- | FragmentColorMaterial | | | v Cf' | FragmentLight |--o-<- Material {Sm,...} | | | | ----------------- | | | --------- | | Clamp | | --------- | Cl | | +---------------- v v ------------ | | | SUM | | | ------------ | --------- | Clamp | --------- | Cf'' | v ------- | | | Fog | | | ------- | v IP Status Silicon Graphics has filed for patent protection for some of the techniques described in this extension document. Issues * does this spec enable a reasonable evolution from a post-texture specular highlight to a full blown per-pixel lighting computation? * can we eliminate some commands and state now and allow the generality to show up later? It doesn't seem like there is much harm in maintaining extra state for computations that isn't actually used since it can be maintained on the host. We eliminate the Lighting environment term since it provides extra capability for how the lighting term is combined. It can show up with the fragment_lighting extension. * given the relaxation in the requirements for how the specular term is computed, it is possible to support multiple specular lights but much less likely to be able to support the same number of full blown fragment lights. New Procedures and Functions void FragmentLightModeliSGIX(enum pname, int param); void FragmentLightModelfSGIX(enum pname, float param); void FragmentLightModelivSGIX(enum pname, int *params); void FragmentLightModelfvSGIX(enum pname, float *params); void FragmentLightiSGIX(enum light, enum pname, int param); void FragmentLightfSGIX(enum light, enum pname, float param); void FragmentLightivSGIX(enum light, enum pname, int *params); void FragmentLightfvSGIX(enum light, enum pname, float *params); void GetFragmentLightivSGIX(enum light, enum value, int *data); void GetFragmentLightfvSGIX(enum light, enum value, float *data); void FragmentMaterialfSGIX(enum face, enum pname, const float param); void FragmentMaterialiSGIX(enum face, enum pname, const int param); void FragmentMaterialfvSGIX(enum face, enum pname, const float *params); void FragmentMaterialivSGIX(enum face, enum pname, const int *params); void FragmentColorMaterialSGIX(enum face, enum mode); void GetFragmentMaterialfvSGIX(enum face, enum pname, float *data); void GetFragmentMaterialivSGIX(enum face, enum pname, int *data); New Tokens Accepted by the parameter of Enable, Disable, and IsEnabled, by the parameter of GetBooleanv, GetIntegerv, GetFloatv, and GetDoublev: FRAGMENT_LIGHTING_SGIX XXXX FRAGMENT_COLOR_MATERIAL_SGIX XXXX FRAGMENT_COLOR_MATERIAL_FACE_SGIX XXXX FRAGMENT_COLOR_MATERIAL_PARAMETER_SGIX XXXX Accepted by the parameter of GetBooleanv, GetIntegerv, GetFloatv, and GetDoublev: MAX_FRAGMENT_LIGHTS_SGIX XXXX MAX_ACTIVE_LIGHTS_SGIX XXXX CURRENT_RASTER_NORMAL_SGIX XXXX Accepted by the parameter of FragmentLightfSGIX, FragmentLightiSGIX, FragmentLightfvSGIX, and FragmentLightivSGIX, and by the parameter of Enable, Disable, and IsEnabled, and by the parameter of GetFragmentLightfvSGIX and GetFragmentLightivSGIX: FRAGMENT_LIGHT0_SGIX XXXX . . . FRAGMENT_LIGHT7_SGIX XXXX Accepted by the parameter of FragmentLightModeliSGIX, FragmentLightModelfSGIX, FragmentLightModelivSGIX, FragmentLightModelfvSGIX, GetBooleanv, GetIntegerv, GetFloatv, and GetDoublev: FRAGMENT_LIGHT_MODEL_LOCAL_VIEWER_SGIX XXXX FRAGMENT_LIGHT_MODEL_TWO_SIDE_SGIX XXXX FRAGMENT_LIGHT_MODEL_AMBIENT_SGIX XXXX FRAGMENT_LIGHT_MODEL_NORMAL_INTERPOLATION_SGIX XXXX Additions to Chapter 2 of the 1.1 Specification (OpenGL Operation) Section 2.12 Current Raster Position ... The current raster position consists of three window coordinates xw, yw, and zw, a clip corrdinate wc value, an eye coordinate distance, a valid bit, and associated data consisting of a color, normal, and texture coordinates. It is set ... ... The current raster position requires five single-precision floating point values for its xw, yw, and zw window coordinates, its wc clip coordinate, and its eye coordinate distance, a single valid bit, a color (RGBA and color index), normal, and texture coordinates for associated data. In the initial state, the coordinates and texture coordinates are both (0,0,0,1), the eye coordinate distance is 0, the valid bit is set, the associated RGBA color is (1,1,1,1), the associated color index is 1, and the associated normal is (0,0,1). In RGBA mode, the associated color index always has its initial value; in color index mode, the RGBA color always maintains its initial value. Section 2.13 Colors and Coloring ... Next vertex lighting, if enabled produces a color. If vertex lighting is disabled, the current color is used in further processing. After vertex lighting, RGBA colors are clamped to the range [0,1]. A color index is converted to fixed-point and then its integer portion is masked (see section 2.13.16). After clamping or masking, a primitive may be flatshaded, indicating that all vertices of the primitive are to have the same color (and normal). Finally, a primitive is clipped, then colors (texture coordinates and normals) must be computed at the vertices introduced or modified by clipping. Additions to Chapter 3 of the 1.1 Specification (Rasterization) Section 3.6.3 Rasterization of Pixel Rectangles Conversion to Fragments ... A fragment arising from a group consisting of color data takes on the color index or color components of the group; the depth, normal and texture coordinates are taken from the current raster position's associated data. A fragment arising from a depth component takes the component's depth value; the color, normal, and texture coordinate are given by those associated with the current raster position. In both cases texture coordinates s, t, and r are preplaced with s/q, t/q, and r/q, respectively. If q is less than or equal to zero the results are undefined. Groups arising from DrawPixels with a of STENCIL_INDEX are treated specially and are described in section 4.3.1. Before Section 3.9 Fog insert: Section 3.9 Fragment Lighting If enabled, fragment lighting computes a color for each rasterized fragment by applying an equation defined by a client-specified lighting model to a collection of parameters that can include the fragment coordinates, the coordinates of one or more light sources, the fragment normal, and parameters defining the characteristics of the light source and current fragment material. Fragment lighting is only defined for RGBA mode, it has no effect in color index mode. Fragment lighting may be in one of two states: 1. Lighting Off. In this state the color assigned to a fragment is the rasterized fragment's post-texturing color. 2. Lighting On. In this state the color assigned to a fragment is the result of summing the rasterized fragment's post-texturing color and a color computed from the current fragment lighting parameters. Fragment lighting is turned either on or off using the generic Enable or Disable commands with the symbolic value FRAGMENT_LIGHTING_SGIX. 3.9.2 Lighting Operation The desired general equation for the fragment illumination model is: Cl = Em emissive + Am*As ambient material*scene ambient color SUM{_i = 0 through Nf-1} { + Atten_i*SpotL_i*{ distance/spot light attenuation + Am*Al_i ambient material*ambient light + Dm*Dl_i*(N.L_i) diffuse material*diffuse light + Sm*Sl_i*(N.H_i)^n specular material*specular light } } Nf is the number of fragment light sources N is the fragment normal vector L_i is the direction vector from the fragment position to the light source H_i is the half angle vector n is the specular exponent (shininess) Subset the equation to the specular term: I[i] = Sm*Sl*(N.H_i)^n) and I' = SUM{i = 0 through Nf-1} I[i] (3.1) Equation (3.1) is essentially the same as the specular term of the vertex lighting equation described in section 2.13.1 for a single light source. In order to compute the illumination terms for each fragment, the eye coordinates of the fragment can be used to compute the light direction, half angle vector, and attenuation factor in a manner similar to that used in the vertex lighting computations. It is permissible for an implementation to approximate these by computing these values as well as the normal vector at the vertices and interpolating and renormalizing the results, or by computing the entire equation at the vertices and interpolating the color. Fragment material state is maintained which is distinct from the vertex material state. The fragment material state consists of emission, ambient, diffuse, specular and shininess terms for both the front and back face of a primitive though only the specular and shininess terms are used by this extension. Unlike vertex lighting, the fragment material state is constant across a primitive since it is resolved during rasterization. The results of the back face computation described in section 3.5.1 are used to determine whether the front material or back material is used when two sided lighting is enabled. There is separate state for each fragment light source. The fragment light source parameters are the same as the vertex light source parameters described in section 2.13.1. The minimum number of fragment light sources is 1. The number of available fragment light sources can be queried by issuing the Get command with the parameter set to MAX_FRAGMENT_LIGHTS_SGIX. Distinct lighting model state is also maintained for vertex lighting and fragment lighting. The lighting model state is described in section 2.13.1. Fragment lighting model state includes one additional parameter, FRAGMENT_LIGHT_MODEL_NORMAL_INTERPOLATION_SGIX, which controls how normals are selected for use in the fragment lighting computations for a primitive. If FLAT is selected for the lighting model, the normal from the provoking vertex (as described in Section 2.13.7 Flatshading) of the primitive for all fragment lighting computations for the primitive. If SMOOTH is specified a normal is computed for each fragment using the normals from all of the vertices of the primitive. Fragment lighting differs from vertex lighting in that all components of lighting parameters which are of type color in Table 2.7 are clamped to the range [0,1] when they are specified. Equation 3.2 is evaluated for each light source and the resulting colors are summed. The resulting color components are clamped to the range [0,1] and then passed to the lighting environment computation. 3.9.3 Lighting Parameter Specification GetFragmentMaterialfvSGIX and GetFragmentMaterialivSGIX. The fragment material state can be set with the commands FragmentMaterialfSGIX, FragmentMaterialfvSGIX, FragmentMaterialiSGIX, FragmentMaterialivSGIX using the values AMBIENT, DIFFUSE, SPECULAR, SHININESS and EMISSION. This state can be queried using the commands GetFragmentMaterialfvSGIX and GetFragmentMaterialivSGIX. Lighting parameters for fragment light i can be modified by issuing the commands FragmentLightfSGIX, FragmentLightiSGIX, FragmentLightfvSGIX, and FragmentLightivSGIX with the parameter set to FRAGMENT_LIGHTi_SGIX. The lighting parameters for fragment light i can be queried by issuing the commands GetFragmentLightfvSGIX and GetFragmentLightivSGIX with the parameter set to FRAGMENT_LIGHTi_SGIX. Lighting model parameters for fragment lighting can be modified using the commands FragmentLightModel{T}SGIX, FragmentLightModel{T}vSGIX. The lighting model parameters can be queried by issuing the Get command parameter set to the appropriate fragment lighting model parameter: FRAGMENT_LIGHT_MODEL_LOCAL_VIEWER_SGIX, FRAGMENT_LIGHT_MODEL_TWO_SIDE_SGIX, FRAGMENT_LIGHT_MODEL_AMBIENT_SGIX or FRAGMENT_LIGHT_MODEL_NORMAL_INTERPOLATION_SGIX. 3.9.4 FragmentColorMaterial It is possible to replace one or more fragment material properties terms in Equation 3.1 with the fragment's pre-texturing color, causing these color values to be used during the lighting computation. This behavior is enabled and disabled by calling Enable and Disable with the symbolic value FRAGMENT_COLOR_MATERIAL. The command that controls which of these modes is selected is void FragmentColorMaterial(enum face, enum mode); is one of FRONT, BACK, or FRONT_AND_BACK, indicating whether the front material, back material, or both are affected by the pre-texturing color. is one of EMISSION, AMBIENT, DIFFUSE, SPECULAR, or AMBIENT_AND_DIFFUSE and specifies which material property or properties are subsituted with the pre-texturing color. The substutions do not affect the material state. When FragmentColorMaterial is disabled the values in the fragment material state are used. GetFragmentMaterial returns the fragment material last specified with FragmentMaterial, regardless of whether FragmentColorMaterial is enabled. Although all of the fragment material parameters may be substituted, only substituting the SPECULAR material property will affect the result of the lighting computation. 3.9.5 Interactions with Vertex Lighting In order to allow implementions to share resources for vertex lighting and fragment lighting, an implementation may limit the maximum number of combined vertex and fragment lights to a number less than the sum of MAX_LIGHTS and MAX_FRAGMENT_LIGHTS_SGIX. This limit can be queried using the Get command with parameter MAX_ACTIVE_LIGHTS_SGIX. State for all fragment and vertex lights is always maintained. When multiple lights are enabled, priority is given to vertex lights starting with LIGHT0 through LIGHT where is equal to MAX_LIGHTS, followed by FRAGMENT_LIGHT0_SGIX through FRAGMENT_LIGHT_SGIX where is equal to MAX_FRAGMENT_LIGHTS_SGIX. Additions to Chapter 4 of the 1.1 Specification (Per-Fragment Operations and the Frame Buffer) None Additions to Chapter 5 of the 1.1 Specification (Special Functions) None Additions to Chapter 6 of the 1.1 Specification (State and State Requests) TBD Additions to the GLX Specification TBD Dependencies on SGIX_color_range If SGIX_color_range is implemented, then the components of lighting parameters of type color, the result of evaluating the lighting equation and the results of evaluating the lighting environment are clamped to the extended color range rather than [0,1]. Errors INVALID_ENUM is generated if FragmentMaterial{T}SGIX, FragmentMaterial{T}vSGIX, or FragmentColorMaterialSGIX, parameter is not FRONT, BACK or FRONT_AND_BACK. INVALID_ENUM is generated if FragmentMaterial{T}SGIX or FragmentMaterial{T}vSGIX parameter is not AMBIENT, DIFFUSE, SPECULAR, EMISSION, SHININESS, or AMBIENT_AND_DIFFUSE. INVALID_ENUM is generated if GetFragmentMaterial{T}vSGIX parameter is not FRONT or BACK. INVALID_ENUM is generated if GetFragmentMaterial{T}vSGIX parameter is not AMBIENT, DIFFUSE, SPECULAR, EMISSION, or SHININESS, INVALID_ENUM if FragmentColorMaterialSGIX parameter is not EMISSION, AMBIENT, DIFFUSE, SPECULAR, or AMBIENT_AND_DIFFUSE INVALID_ENUM if LightEnviSGIX parameter is not LIGHT_ENV_MODE_SGIX or if parameter is not REPLACE, MODULATE, or ADD. INVALID_ENUM is generated if FragmentLightModel{T}SGIX is not FRAGMENT_LIGHT_MODEL_LOCAL_VIEWER_SGIX, FRAGMENT_LIGHT_MODEL_TWO_SIDE_SGIX or FRAGMENT_LIGHT_MODEL_NORMAL_INTERPOLATION_SGIX or if FragmentLightModel{T}vSGIX, parameter is not FRAGMENT_LIGHT_MODEL_AMBIENT_SGIX, FRAGMENT_LIGHT_MODEL_LOCAL_VIEWER_SGIX FRAGMENT_LIGHT_MODEL_TWO_SIDE_SGIX or FRAGMENT_LIGHT_MODEL_NORMAL_INTERPOLATION_SGIX. INVALID_ENUM is generated if FragmentLight{T}SGIX, FragmentLight{T}vSGIX, or GetFragmentLight{T}vSGIX parameter is not FRAGMENT_LIGHT0_SGIX ... FRAGMENT_LIGHT_SGIX where n is one minus the number of supported fragment lights, or if FragmentLight{T}SGIX parameter is not SPOT_EXPONENT, SPOT_CUTOFF, CONSTANT_ATTENUATION, LINEAR_ATTENUATION, or QUADRATIC_ATTENUATION, or if FragmentLight{T}vSGIX or GetFragmentLight{T}vSGIX parameter is not AMBIENT, DIFFUSE, SPECULAR, POSITION, SPOT_DIRECTION, SPOT_EXPONENT, SPOT_CUTOFF, CONSTANT_ATTENUATION, LINEAR_ATTENUATION, or QUADRATIC_ATTENUATION. INVALID_VALUE is generated if FragmentLight{T}SGIX or FragmentLight{T}vSGIX parameter if a spot exponent value is specified outside the range [0,128], or if spot cutoff is specified outside the range [0,90] (except for the special value 180), or if a negative attenuation factor is specified. INVALID_OPERATION is generated if FragmentMaterial{T}SGIX, FragmentMaterial{T}vSGIX, FragmentColorMaterialSGIX, GetFragmentMaterial{T}vSGIX, LightEnviSGIX, FragmentLight{T}SGIX, FragmentLight{T}vSGIX, FragmentLightModel{T}SGIX, FragmentLightModel{T}vSGIX or GetFragmentLight{T}vSGIX is executed between execution of Begin and the corresponding execution of End. New State Get Value Get Command Type Initial Value Attribute --------- ----------- ---- ------------- --------- FRAGMENT_LIGHTING_SGIX IsEnabled B False lighting/enable FRAGMENT_COLOR_MATERIAL_SGIX IsEnabled B False lighting/enable FRAGMENT_COLOR_MATERIAL_PARAMETER_SGIX GetIntegerv Z5 AMBIENT_AND_DIFFUSE lighting FRAGMENT_COLOR_MATERIAL_FACE_SGIX GetIntegerv Z3 FRONT_AND_BACK lighting AMBIENT GetFragmentMaterialfvSGIX 2xC (0.2,0.2,0.2,1.0) lighting DIFFUSE GetFragmentMaterialfvSGIX 2xC (0.8,0.8,0.8,1.0) lighting SPECULAR GetFragmentMaterialfvSGIX 2xC (0.0,0.0,0.0,1.0) lighting EMISSION GetFragmentMaterialfvSGIX 2xC (0.0,0.0,0.0,1.0) lighting SHININESS GetFragmentMaterialfvSGIX 2xR 0.0 lighting FRAGMENT_LIGHT_MODEL_AMBIENT_SGIX GetFloatv C (0.2,0.2,0.2,0.2) lighting FRAGMENT_LIGHT_MODEL_LOCAL_VIEWER_SGIX GetBooleanv B False lighting FRAGMENT_LIGHT_MODEL_TWO_SIDE_SGIX GetBooleanv B False lighting FRAGMENT_LIGHT_MODEL_NORMAL_INTERPOLATION_SGIX GetIntegerv Z2 SMOOTH lighting AMBIENT GetFragmentLightfvSGIX 1*xC (0.0,0.0,0.0,1.0) lighting DIFFUSE GetFragmentLightfvSGIX 1*xC see 3.x lighting SPECULAR GetFragmentLightfvSGIX 1*xC see 3.x lighting POSITION GetFragmentLightfvSGIX 1*xP (0.0,0.0,1.0,0.0) lighting CONSTANT_ATTENUATION GetFragmentLightfvSGIX 1*xR 1.0 lighting LINEAR_ATTENUATION GetFragmentLightfvSGIX 1*xR+ 0.0 lighting QUADRATIC_ATTENUATION GetFragmentLightfvSGIX 1*xR+ 0.0 lighting SPOT_DIRECTION GetFragmentLightfvSGIX 1*xD (0.0,0.0,-1.0) lighting SPOT_EXPONENT GetFragmentLightfvSGIX 1*xR+ 0.0 lighting SPOT_CUTOFF GetFragmentLightfvSGIX 1*xR+ 180.0 lighting FRAGMENT_LIGHTi_SGIX IsEnabled 1*xB False lighting/enable LIGHT_ENV_MODE_SGIX GetIntegerv Z3 REPLACE lighting CURRENT_RASTER_NORMAL_SGIX GetFloatv N (0,0,1) current New Implementation Dependent State Get Value Get Command Type Minimum Value --------- ----------- ---- ------------- MAX_FRAGMENT_LIGHTS_SGIX GetIntegerv Z+ 1 MAX_ACTIVE_LIGHTS_SGIX GetIntegerv z+ MAX_LIGHTS