| Name |
| |
| ARB_vertex_blend |
| |
| Name Strings |
| |
| GL_ARB_vertex_blend |
| |
| Contact |
| |
| Evan Hart, NVIDIA (ehart 'at' nvidia.com) |
| Tom Frisinger, AMD (tom.frisinger 'at' amd.com) |
| |
| Notice |
| |
| Copyright (c) 2000-2013 The Khronos Group Inc. Copyright terms at |
| http://www.khronos.org/registry/speccopyright.html |
| |
| Specification Update Policy |
| |
| Khronos-approved extension specifications are updated in response to |
| issues and bugs prioritized by the Khronos OpenGL Working Group. For |
| extensions which have been promoted to a core Specification, fixes will |
| first appear in the latest version of that core Specification, and will |
| eventually be backported to the extension document. This policy is |
| described in more detail at |
| https://www.khronos.org/registry/OpenGL/docs/update_policy.php |
| |
| Status |
| |
| Complete. Approved by ARB on September 19, 2000. |
| |
| Version |
| |
| Last Modified Date: November 4, 2006 |
| Revision: 1.3 |
| |
| Number |
| |
| ARB Extension #15 |
| |
| Dependencies |
| |
| OpenGL 1.0 is required. |
| This extension is written against the OpenGL 1.2.1 Specification. |
| |
| Overview |
| |
| This extension provides the ability to replace the single |
| modelview transformation with a set of n vertex units. (Where |
| n is constrained to an implementation defined maximum.) Each |
| unit has its own modelview transform matrix. For each unit, |
| there is a current weight associated with the vertex. When |
| this extension is enabled the vertices are transformed by |
| the modelview matrices of all of the enabled units. Afterward, |
| these results are scaled by the weights for the respective |
| units and then summed to create the eye-space vertex. A |
| similar procedure is followed for the normals, except they |
| are transformed by the inverse transpose of the modelview |
| matrices. |
| |
| This extension is an orthoganalized version of functionality |
| already provided by other 3D graphics API's. |
| |
| |
| IP Status |
| |
| Unknown, but believed to be none. |
| |
| Issues |
| |
| |
| Should an indexed form of matrix addressing be used? |
| |
| No, this should be added as an additional extension. |
| |
| Should integer blending weights be allowed? |
| |
| Yes, this was an over-sight in the original spec. Integer |
| formats allow for the potential to provide smaller data |
| types to the API. Integer data types are always mapped |
| to floats in the same manner as colors. |
| |
| Should the blending weights be forced to sum to 1? |
| |
| No, it should be provided as a convenience to developers, |
| since it is the most common case. Additionally, it should |
| be noted that even if the weights do not sum to one, |
| the result of the modelview transformation provides an |
| eye coordinate whose homogenous coordinate is equivalent |
| to the homogeneous coordinate after the transformation |
| had the weights been scaled to sum to one. |
| |
| Additionally, NORMALIZE should in general be left on to |
| prevent non-unit normals. |
| |
| What about projective modelview matrices? |
| |
| Projective modelview matrices can cause problems with many |
| other features in GL, so this should not be a problem in |
| practice. This extension makes no attempts to handle |
| projective modelview matrices. |
| |
| Should the set of modelview matrices affect parts of GL other |
| than vertices? |
| |
| No, this seems to confuse the operation, and it forces |
| vertex components to affect setting of GL state. |
| |
| Some transformations may cause the normals to be transformed in |
| such a way that they no longer represent the tangent plane to |
| the surface. |
| |
| This is a basic property of the math of the technique. In |
| general with these varying transformations, it is impossible |
| to maintain the normal as the tangent plane to the surface |
| without topological information. |
| |
| Lacking the topological data, the best approximation is to |
| transform the normals by the inverse transpose of the |
| blend of the modelview matrices. As the inverse per-vertex |
| may be computationally impractical, a slightly less accurate |
| blend of inverse transpose matrices is allowed as the |
| transformation. |
| |
| When the less accurate blend is used, the normals will only |
| be identical to the normals formed by the more correct math |
| when the blending matrices are pair-wise orthogonal and |
| the sum of the square of the weights is equal to one. |
| |
| Should weights be specified as vectors rather than independent |
| scalars? |
| |
| Yes, this removes little flexibility and significantly |
| reduces the call overhead. |
| |
| |
| New Procedures and Functions |
| |
| void Weight{bsifd ubusui}vARB(int size, T* weights) |
| |
| void WeightPointerARB(int size, enum type, sizei stride, |
| void *pointer) |
| |
| void VertexBlendARB(int count) |
| |
| |
| New Tokens |
| |
| Accepted by the <value> parameters of GetBooleanv, GetIntegerv, |
| GetFloatv, and GetDoublev: |
| |
| MAX_VERTEX_UNITS_ARB 0x86A4 |
| ACTIVE_VERTEX_UNITS_ARB 0x86A5 |
| |
| Accepted by the <cap> parameters of Enable and Disable, by the |
| <value> parameter of IsEnabled, GetBooleanv, GetIntegerv, |
| GetFloatv, and GetDoublev: |
| |
| WEIGHT_SUM_UNITY_ARB 0x86A6 |
| VERTEX_BLEND_ARB 0x86A7 |
| |
| Accepted by the <mode> parameter of MatrixMode and by the |
| <value> parameter of GetBooleanv, GetIntegerv, GetFloatv, and |
| GetDoublev. |
| |
| MODELVIEW0_ARB: 0x1700 (alias to MODELVIEW) |
| MODELVIEW1_ARB: 0x850a |
| MODELVIEW2_ARB: 0x8722 |
| MODELVIEW3_ARB: 0x8723 |
| MODELVIEW4_ARB: 0x8724 |
| MODELVIEW5_ARB: 0x8725 |
| MODELVIEW6_ARB: 0x8726 |
| MODELVIEW7_ARB: 0x8727 |
| MODELVIEW8_ARB: 0x8728 |
| MODELVIEW9_ARB: 0x8729 |
| MODELVIEW10_ARB: 0x872A |
| MODELVIEW11_ARB: 0x872B |
| MODELVIEW12_ARB: 0x872C |
| MODELVIEW13_ARB: 0x872D |
| MODELVIEW14_ARB: 0x872E |
| MODELVIEW15_ARB: 0x872F |
| MODELVIEW16_ARB: 0x8730 |
| MODELVIEW17_ARB: 0x8731 |
| MODELVIEW18_ARB: 0x8732 |
| MODELVIEW19_ARB: 0x8733 |
| MODELVIEW20_ARB: 0x8734 |
| MODELVIEW21_ARB: 0x8735 |
| MODELVIEW22_ARB: 0x8736 |
| MODELVIEW23_ARB: 0x8737 |
| MODELVIEW24_ARB: 0x8738 |
| MODELVIEW25_ARB: 0x8739 |
| MODELVIEW26_ARB: 0x873A |
| MODELVIEW27_ARB: 0x873B |
| MODELVIEW28_ARB: 0x873C |
| MODELVIEW29_ARB: 0x873D |
| MODELVIEW30_ARB: 0x873E |
| MODELVIEW31_ARB: 0x873F |
| |
| Accepted by the <value> parameter of GetBooleanv, GetIntegerv, |
| GetFloatv, and GetDoublev: |
| |
| CURRENT_WEIGHT_ARB 0x86A8 |
| |
| Accepted by the <value> parameter of GetBooleanv, GetIntegerv, |
| GetFloatv, and GetDoublev: |
| |
| WEIGHT_ARRAY_TYPE_ARB 0x86A9 |
| WEIGHT_ARRAY_STRIDE_ARB 0x86AA |
| WEIGHT_ARRAY_SIZE_ARB 0x86AB |
| |
| Accepted by the <pname> parameter of GetPointerv: |
| WEIGHT_ARRAY_POINTER_ARB 0x86AC |
| |
| Accepted by the <cap> parameters of EnableClientState and |
| DisableClientState, by the <value> parameter of IsEnabled, |
| GetBooleanv, GetIntegerv, GetFloatv, and GetDoublev: |
| |
| WEIGHT_ARRAY_ARB 0x86AD |
| |
| Additions to Chapter 2 of the OpenGL 1.2.1 Specification (Operation) |
| |
| - (2.6, p. 12) Second paragraph changed to: |
| |
| "Each vertex is specified with two, three, or four |
| coordinates. In addition, a current normal, current texture |
| coordinates, current color, and a set of current weights |
| may be used in processing each vertex. Normals are used |
| by the GL in lighting calculations; the current normal is |
| a three-dimensional vector that may be set by sending three |
| coordinates that specify it. Texture coordinates determine |
| how a texture image is mapped onto a primitive. Weights are |
| used to blend between vertex transformations." |
| |
| - (2.6.3, p. 19) First paragraph changed to: |
| |
| "The only GL commands that are allowed within Begin/End |
| pairs are the commands for specifying vertex coordinates, |
| vertex color, normal coordinates, texture coordinates, and |
| weights (Vertex, Color, Index, Normal, TexCoord, |
| WeightvARB), the ArrayElement command (see section 2.8), |
| the EvalCoord and EvalPoint commands (see section 5.1), |
| commands for specifying lighting material parameters |
| (Material commands; see section 2.13.2), display list |
| invocation commands (CallList and CallLists; see section |
| 5.4), and the EdgeFlag command. Executing any other GL |
| command between the execution of Begin and the |
| corresponding execution of End results in the error |
| INVALID_OPERATION. Executing Begin after Begin has already |
| been executed but before an End is executed generates the |
| INVALID_OPERATION error, as does executing End without a |
| previous corresponding Begin." |
| |
| - (2.7, p. 20) Added after the third paragraph: |
| |
| "The current weights are set using |
| |
| void Weight{bsifd ubusui}vARB(int size, T* weights); |
| |
| the floating point values are assigned to the current |
| weight vector. The first <size> current weights are |
| replaced with <weights> such that: |
| |
| w[i] = <weights>[i] |
| |
| When WEIGHT_SUM_UNITY_ARB is enabled, |
| |
| <size>-1 |
| w[<size>] = 1 - SUM <weights>[i] |
| i=0 |
| |
| otherwise the rest of the current weights are set to |
| 0. If <size> is greater than MAX_VERTEX_UNITS_ARB or if |
| WEIGHT_SUM_UNITY_ARB is enabled and <size> equals |
| MAX_VERTEX_UNITS_ARB, then the error INVALID_VALUE is |
| generated. When the values are supplied as byte, short, |
| int, or their unsigned counterparts, they are converted to |
| floating-point values as indicated for the corresponding |
| type in Table 2.6." |
| |
| - (2.8, p. 21) First paragraph changed to read: |
| |
| "The vertex specification commands described in section 2.7 |
| accept data in almost any format, but their use requires |
| many command executions to specify even simple geometry. |
| Vertex data may also be placed into arrays that are stored |
| in the client's address space. Blocks of data in these |
| arrays may then be used to specify multiple geometric |
| primitives through the execution of a single GL command. |
| The client may specify an implementation dependent set of |
| arrays: one each to store edge flags, texture coordinates, |
| colors, color indices, normals, vertices, and weights. |
| The commands |
| |
| void EdgeFlagPointer( sizei stride, void *pointer); |
| |
| void TexCoordPointer( int size, enum type, sizei stride, |
| void *pointer ); |
| |
| void ColorPointer( int size, enum type, sizei stride, |
| void *pointer ); |
| |
| void IndexPointer( enum type, sizei stride, void |
| *pointer ); |
| |
| void NormalPointer( enum type, sizei stride, void |
| *pointer ); |
| |
| void VertexPointer( int size, enum type, sizei stride, |
| void *pointer ); |
| |
| void WeightPointerARB( int size, enum type, |
| sizei stride, void *pointer) |
| |
| describe the locations and organizations of these arrays. |
| For each command, type specifies the data type of the |
| values stored in the array. Because edge flags are always |
| type boolean, EdgeFlagPointer has no type argument. Size, |
| when present, indicates the number of values per vertex |
| that are stored in the array. Because normals are always |
| specified with three values, NormalPointer has no size |
| argument. Likewise, because color indices, edge flags, and |
| weights are always specified with a single value, |
| IndexPointer, and EdgeFlagPointer also have no size |
| argument. Table 2.4 indicates the allowable values for size |
| and type (when present). For type the values BYTE, SHORT, |
| INT, FLOAT, and DOUBLE indicates types byte, short, int, |
| float, and double, respectively; and the values |
| UNSIGNED_BYTE, UNSIGNED_SHORT, and UNSIGNED_INT indicate |
| types ubyte, ushort, and uint, respectively. The error |
| INVALID_VALUE is generated if size is specified with |
| a value other than that indicated in the table, or if the |
| <size> parameter to WeightPointerARB is outside the range |
| allowed for WeightvARB in section 2.7." |
| |
| - (2.8, p. 22) Change table 2.4 to read: |
| |
| Command Sizes Types |
| ------- ----- ----- |
| VertexPointer 2,3,4 short, int, float, double |
| NormalPointer 3 byte, short, int, float, double |
| ColorPointer 3,4 byte, ubyte, short, ushort, |
| int, uint, float, double |
| IndexPointer 1 ubyte, short, int, float, |
| double |
| TexCoordPointer 1,2,3,4 short, int, float, double |
| EdgeFlagPointer 1 boolean |
| WeightPointerARB 1 ... byte, ubyte, short, ushort, |
| MAX_VERTEX_UNITS_ARB int, uint, float, double |
| |
| |
| - (2.8 p. 23) Change paragraph two to: |
| |
| "An individual array is enabled or disabled by calling one |
| of |
| |
| void EnableClientState( enum array ); |
| void DisableClientState( enum array ); |
| |
| with array set to EDGE_FLAG_ARRAY, TEXTURE_COORD_ARRAY, |
| COLOR_ARRAY, INDEX_ARRAY, NORMAL_ARRAY, VERTEX_ARRAY, or |
| WEIGHT_ARRAY_ARB, for the edge flag, texture coordinate, |
| color, color index, normal, vertex, or weight array, |
| respectively." |
| |
| - (2.8 p. 23) Change paragraph three to: |
| |
| "The ith element of every enabled array is transferred to |
| the GL by calling |
| |
| void ArrayElement( int i ); |
| |
| For each enabled array, it is as though the corresponding |
| command form section 2.7 or 2.6.2 were called with a |
| pointer to element i. For the vertex array, the |
| corresponding command is Vertex[size][type]v, where size is |
| one of [2,3,4], and type is one of [s,i,f,d], corresponding |
| to array types short, int, float, and double respectively. |
| The corresponding commands for the edge flag, texture |
| coordinate, color, color index, normal, and weight arrays |
| are EdgeFlagv, TexCoord[size][type]v, Color[size][type]v, |
| Index[type]v, Normal[type]v, and Weight[type]vARB, |
| respectively. The <size> parameter to WeightvARB is the |
| current <size> for the weight array. If the vertex array |
| is enabled, it is as though Vertex[size][type]v is executed |
| last, after the executions of the other corresponding |
| commands." |
| |
| - (2.10 p. 28) Added after the second paragraph: |
| |
| "Alternatively, the model-view transformation may be |
| performed by a set of model-view matrices when vertex |
| blending is enabled. Enabling and disabling of vertex |
| blending is handled by Enable or Disable with the argument |
| of VERTEX_BLEND_ARB. When blending is enabled, the vertex |
| is transformed by multiple model-view transformations. |
| The number of active transformations applied is set by |
| |
| void VertexBlendARB(int count) |
| |
| where count is the number of transformations to blend. |
| If count is greater than the implementation defined |
| maximum number of transformations reported in |
| MAX_VERTEX_UNITS_ARB, then the error |
| INVALID_VALUE is generated." |
| |
| - (2.10 p. 29) Add after the second paragraph: |
| |
| "When vertex blending is enabled, the vertex's eye |
| coordinates are found as: |
| |
| (xe) n-1 (xo) |
| (ye) = SUM w_i * M_i * (yo) |
| (ze) i=0 (zo) |
| (we) (wo) |
| |
| where M_i is the i'th model-view matrix, w_i is the |
| vertex's associated weight for vertex unit i, |
| |
| and |
| |
| n = ACTIVE_VERTEX_UNITS_ARB |
| " |
| |
| - (2.10.2 p. 31) Change the first paragraph to: |
| |
| "The projection matrix and model-view matrices are set |
| with a variety of commands. The affected matrix is |
| determined by the current matrix mode. The current |
| matrix mode is set with |
| |
| void MatrixMode( enum mode ); |
| |
| which takes one of the pre-defined constants TEXTURE, |
| MODELVIEW, COLOR, PROJECTION, or MODELVIEWn_ARB. TEXTURE |
| is described later in section 2.10.2, and COLOR is |
| described in section 3.6.3. If the current matrix mode is |
| MODELVIEW, the matrix operations apply to the model-view |
| matrix; if PROJECTION, then they apply to the projection |
| matrix; if MODLEVIEWn_ARB, then they apply to the n'th |
| model-view matrix. MODELVIEW0_ARB is aliased to |
| MODELVIEW." |
| |
| - (2.10.2 p. 34) Changed the second paragraph to read: |
| |
| "There is a stack of matrices for each of the matrix |
| modes. For MODELVIEWn mode, the stack depth is at least 32 |
| (that is, there is a stack of at least 32 MODELVIEWn |
| matrices). Additionally, all modelview matrices must |
| have the same stack depth. ..." |
| |
| - (2.10.2 p. 34) Changed the third paragraph to read: |
| |
| "... and a stack of at least 32 4 x 4 matrices with an |
| associated stack pointer for each MODELVIEWn. ..." |
| |
| |
| - (2.10.3 p. 35) Added after the third paragraph: |
| |
| "When vertex blending is enabled, the normal is transformed |
| to eye space by: |
| |
| n-1 |
| (nx' ny' nz') = (nx ny nz) Inv ( SUM w_i * Mu_i) |
| i=0 |
| |
| Alternatively implementations may choose to transform the |
| normal to eye-space by: |
| |
| n-1 |
| (nx' ny' nz') = SUM w_i * (nx ny nz) Inv(Mu_i) |
| i=0 |
| |
| where Mu_i is the upper leftmost 3x3 matrix taken from the |
| model-view for vertex unit i, w_i is the vertex's |
| associated weight for vertex unit i, and |
| |
| n = ACTIVE_VERTEX_UNITS_ARB" |
| |
| |
| - (2.10.3 p. 36) Added after the second paragraph: |
| |
| "When vertex blending is enabled, rescaling is applied |
| within each vertex unit independently. The rescale factor |
| for each unit is derived from the modelview matrix for that |
| unit. Normalization is applied to the transformed, blended |
| normal." |
| |
| Additions to Chapter 3: |
| |
| None |
| |
| Additions to Chapter 4: |
| |
| None |
| |
| Additions to Chapter 5: |
| |
| None |
| |
| Additions to Chapter 6: |
| |
| None |
| |
| Additions to the GLX Specification |
| |
| None |
| |
| GLX Protocol |
| |
| Nine new GL rendering commandsl are added. The following commands |
| are sent to the server as part of a glXRender request: |
| |
| WeightbvARB |
| |
| 2 8+n rendering command length |
| 2 220 rendering command opcode |
| 4 INT32 size |
| 1*n INT8 weights |
| |
| WeightubvARB |
| |
| 2 8+n rendering command length |
| 2 221 rendering command opcode |
| 4 INT32 size |
| 1*n CARD8 weights |
| |
| WeightsvARB |
| |
| 2 8+2*n rendering command length |
| 2 222 rendering command opcode |
| 4 INT32 size |
| 2*n INT16 weights |
| |
| WeightusvARB |
| |
| 2 8+2*n rendering command length |
| 2 223 rendering command opcode |
| 4 INT32 size |
| 2*n CARD16 weights |
| |
| WeightivARB |
| |
| 2 8+4*n rendering command length |
| 2 224 rendering command opcode |
| 4 INT32 size |
| 4*n INT32 weights |
| |
| WeightuivARB |
| |
| 2 8+4*n rendering command length |
| 2 225 rendering command opcode |
| 4 INT32 size |
| 4*n CARD32 weights |
| |
| VertexBlendARB |
| |
| 2 8 rendering command length |
| 2 226 rendering command opcode |
| 4 INT32 count |
| |
| WeightfvARB |
| |
| 2 8+4*n rendering command length |
| 2 227 rendering command opcode |
| 4 INT32 size |
| 4*n FLOAT32 weights |
| |
| WeightdvARB |
| |
| 2 8+8*n rendering command length |
| 2 228 rendering command opcode |
| 4 INT32 size |
| 8*n FLOAT64 weights |
| |
| Errors |
| |
| INVALID_VALUE is generated if the <size> parameter for |
| WeightvARB or WeightPointerARB is greater than |
| MAX_VERTEX_UNITS_ARB, or if WEIGHT_SUM_UNITY_ARB is enabled |
| and <size> is equal to MAX_VERTEX_UNITS_ARB |
| |
| INVALID_VALUE is generated if the <count> parameter to |
| VertexBlendARB is greater than MAX_VERTEX_UNITS_ARB or |
| if <count> is equal to zero. |
| |
| New State |
| |
| Modified State in Table 6.5: |
| |
| Get Value Get Command Type Initial Value Attribute |
| --------- ----------- ---- ------------- --------- |
| CURRENT_WEIGHT_ARB GetFloatv Rn n=0 - 1.0 current |
| n>0 - 0.0 |
| |
| Modified State in Table 6.6: |
| |
| Get Value Get Command Type Initial Value Attribute |
| --------- ----------- ---- ------------- --------- |
| WEIGHT_ARRAY_ARB IsEnabled 1*B False vert-array |
| WEIGHT_ARRAY_TYPE_ARB GetIntegerv 1*Z2 FLOAT vert-array |
| WEIGHT_ARRAY_SIZE_ARB GetIntegerv 1*Z+ 0 vert-array |
| WEIGHT_ARRAY_STRIDE_ARB GetIntegerv 1*Z+ 0 vert-array |
| WEIGHT_ARRAY_POINTER_ARB GetPointerv 1*Y 0 vert-array |
| |
| |
| Modified state in Table 6.7: |
| |
| Get Value Get Command Type Initial Value Attribute |
| --------- ----------- ---- ------------- --------- |
| MODELVIEWn_ARB GetFloatv 1*32*xM4 Identity - |
| ACTIVE_VERTEX_UNITS_ARB GetIntegerv Z+ 1 transform |
| VERTEX_BLEND_ARB IsEnabled B False transform |
| enable |
| |
| Modified state in Table 6.25: |
| |
| Get Value Get Command Type Minmum Value Attribute |
| --------- ----------- ---- ------------ --------- |
| MAX_VERTEX_UNITS_ARB GetIntegerv Z+ 2 - |
| |
| Additions to Appendix A: |
| |
| None |
| |
| Revision History |
| |
| * 1.0 (October 16, 2000) - initial version |
| |
| * 1.1 (March 12, 2002) - added GLX protocol for Weight[df]v |
| |
| * 1.2 (March 21, 2002) - correct Weightdv protocol |
| |
| * 1.3 (November 4, 2006) - updated contact info after ATI/AMD merger |
