skia / external / github.com / KhronosGroup / OpenGL-Registry / f06072fd879297ac9979d28fa7c61e78e069866d / . / extensions / ARB / ARB_vertex_blend.txt

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 |