| Name |
| |
| ANGLE_base_vertex_base_instance |
| |
| Name Strings |
| |
| GL_ANGLE_base_vertex_base_instance |
| |
| Contributors |
| |
| Shrek Shao, Google Inc. |
| Contributors to the OES_draw_elements_base_vertex specification |
| Contributors to the EXT_draw_elements_base_vertex specification |
| Contributors to the EXT_multi_draw_arrays specification |
| Contributors to the ARB_shader_draw_parameters specification |
| |
| Contact |
| |
| Shrek Shao (shrekshao 'at' google.com) |
| |
| Status |
| |
| Incomplete |
| |
| Version |
| |
| Last Modified Date: August 13, 2019 |
| Author Revision: 1 |
| |
| Number |
| |
| OpenGL ES Extension XX |
| |
| Dependencies |
| |
| OpenGL ES 3.1 is required. |
| |
| This extension is written against the OpenGL ES 3.1 specification, the |
| OpenGL ES 3.2 specification, and the OpenGL ES Shading Language 3.0 |
| specification. |
| |
| GL_ANGLE_multi_draw is required. |
| |
| Overview |
| |
| This extension exposes the *BaseVertex* draw call in |
| OES_draw_elements_base_vertex/EXT_draw_elements_base_vertex together with |
| their newly added *BaseInstance and MultiDraw* variants in addition to the |
| vertex shader builtins <gl_BaseVertex> and <gl_BaseInstance> exposed by |
| ARB_shader_draw_parameters for OpenGL. |
| |
| *BaseInstance behaves identically to its counterpart draw calls except that |
| <instanceCount> instances of the range of elements are executed and the |
| value of <instance> advances for each iteration. Those attributes that have |
| non-zero values for <divisor>, as specified by VertexAttribDivisor, advance |
| once per <divisor> instances of the set(s) of vertices being rendered. |
| Additionally, <baseInstance> specifies the first element within the |
| instanced vertex attributes. |
| |
| *BaseVertex* is equivalent to its counterpart draw calls except that |
| the value of the base vertex passed into the driver is <baseVertex> instead |
| of zero, and that <instances> of the set of elements are executed and the |
| value of <instance> advances between each set. |
| |
| Additionally, <gl_BaseVertex> and <gl_BaseInstance> builtins are added |
| to the shading language. |
| For any *BaseVertex* draw call variant, the <baseVertex> of the draw may be |
| read by the vertex shader as <gl_BaseVertex>. For non *BaseVertex* calls, |
| the value of <gl_BaseVertex> is 0. |
| For any *BaseInstance draw call variant, the baseInstance of the draw may |
| be read by the vertex shader as <gl_BaseInstance>. For non *BaseInstance |
| calls, the value of <gl_BaseInstance> is 0. |
| |
| IP Status |
| |
| No known IP claims. |
| |
| New Procedures and Functions |
| |
| void DrawArraysInstancedBaseInstanceANGLE(enum mode, |
| GLint first, |
| GLsizei count, |
| GLsizei instanceCount, |
| GLuint baseInstance); |
| |
| void DrawElementsInstancedBaseVertexBaseInstanceANGLE(GLenum mode, |
| GLsizei count, |
| GLenum type, |
| const GLvoid *indices, |
| GLsizei instanceCount, |
| GLint baseVertex, |
| GLuint baseInstance); |
| |
| void MultiDrawArraysInstancedBaseInstanceANGLE(enum mode, |
| const GLsizei drawcount, |
| const GLsizei* counts, |
| const GLsizei* instanceCounts, |
| const GLint* firsts, |
| const GLint* baseInstances); |
| |
| void MultiDrawElementsInstancedBaseVertexBaseInstanceANGLE(enum mode, |
| const GLsizei drawcount, |
| const GLint* counts, |
| GLenum type, |
| const GLvoid* const* indices, |
| const GLsizei* instanceCounts, |
| const GLint* baseVertices, |
| const GLint* baseInstances); |
| |
| New Tokens |
| |
| None. |
| |
| Additions to Chapter 10 of the OpenGL ES 3.2 Specification |
| |
| Section 10.5 Drawing Commands Using Vertex Arrays: |
| |
| The command |
| |
| void DrawArraysInstancedBaseInstanceANGLE (GLenum mode, |
| GLint first, |
| GLsizei count, |
| GLsizei instanceCount, |
| GLuint baseInstance); |
| |
| Behaves identically to DrawArraysInstanced except that <baseInstance> is |
| passed down to DrawArraysOneInstance instead of zero. |
| |
| The base index of the instance may be read by a vertex shader as |
| <gl_BaseInstance>. |
| |
| The command |
| |
| void MultiDrawArraysInstancedBaseInstanceANGLE(GLenum mode, |
| GLsizei drawcount, |
| const GLsizei* counts, |
| const GLsizei* instanceCounts, |
| const GLint* firsts, |
| const GLuint* baseInstances); |
| |
| Behaves identically to DrawArraysInstancedBaseInstanceANGLE except that a |
| list of arrays is specified instead. The number of lists is specified in |
| the <drawcount> parameter. It has the same effect as: |
| |
| for(i=0; i<drawcount; i++) { |
| if (*(counts+i)>0) DrawArraysInstancedBaseInstance( |
| mode, |
| *(counts+i), |
| *(instanceCounts+i), |
| *(firsts+i), |
| *(baseInstance+i) |
| ); |
| } |
| |
| The index of the draw (<i> in the above pseudo-code) may be read by |
| a vertex shader as <gl_DrawID> which is defined in GL_ANGLE_multi_draw. |
| |
| The command |
| |
| void DrawElementsInstancedBaseVertexBaseInstanceANGLE (GLenum mode, |
| GLsizei count, |
| GLenum type, |
| const GLvoid* indices, |
| GLsizei instanceCount, |
| GLint baseVertex, |
| GLuint baseInstance); |
| |
| Behaves identically to DrawElementsInstanced except that <baseVertex> and |
| <baseInstance> are passed down to DrawElementsOneInstance instead of zero. |
| |
| The base index of the vertex may be read by a vertex shader as |
| <gl_BaseVertex>. This value is also added to the <gl_VertexID>. |
| |
| The base index of the instance may be read by a vertex shader as |
| <gl_BaseInstance>. Note that this value is not added to the |
| <gl_InstanceID>. |
| |
| The command |
| |
| void MultiDrawElementsInstancedBaseVertexBaseInstanceANGL(GLenum mode, |
| GLenum type, |
| GLsizei drawcount, |
| const GLsizei* counts, |
| const GLsizei* instanceCounts, |
| const GLvoid* const* indices, |
| const GLint* baseVertices, |
| const GLuint* baseInstances); |
| |
| Behaves identically to DrawElementsInstancedBaseVertexBaseInstanceANGLE |
| except that a list of arrays is specified instead. The number of lists is |
| specified in the <drawcount> parameter. It has the same effect as: |
| |
| for(i=0; i<drawcount; i++) { |
| if (*(counts+i)>0) DrawElementsInstancedBaseVertexBaseInstanceANGLE( |
| mode, |
| *(counts+i), |
| type, |
| *(instanceCounts+i), |
| *(indices+i), |
| *(baseVertices+i), |
| *(baseInstances+i) |
| ); |
| } |
| |
| The index of the draw (<i> in the above pseudo-code) may be read by |
| a vertex shader as <gl_DrawID> which is defined in GL_ANGLE_multi_draw. |
| |
| Errors |
| |
| DrawArraysInstancedBaseInstanceANGLE and |
| DrawElementsInstancedBaseVertexBaseInstanceANGLE |
| generate the same errors as DrawArraysInstanced and DrawElementsInstanced. |
| |
| MultiDrawArraysInstancedBaseInstanceANGLE and |
| MultiDrawElementsInstancedBaseVertexBaseInstanceANGL |
| generate the same errors as DrawArraysInstanced and DrawElementsInstanced, |
| respectively, for any draw <i> where an error is generated. If any call |
| would produce an error, no drawing is performed. |
| |
| The error INVALID_VALUE is generated by the MultiDraw* functions if |
| <drawcount> is less than zero. |
| |
| Modifications to the OpenGL ES Shading Language Specification, Version 3.00 |
| |
| Including the following line in a shader can be used to control the |
| language featured described in this extension: |
| |
| #extension GL_ANGLE_base_vertex_base_instance : <behavior> |
| |
| where <behavior> is as specified in section 3.5. |
| |
| A new preprocessor #define is added to the OpenGL ES Shading Language: |
| |
| #define GL_ANGLE_base_vertex_base_instance 1 |
| |
| Dependencies on GL_OES_draw_elements_base_vertex and |
| GL_EXT_draw_elements_base_vertex |
| |
| If the OpenGL ES context version is less than 3.2, this extension is only |
| available when GL_OES_draw_elements_base_vertex or |
| GL_EXT_draw_elements_base_vertex are available. |
| |
| Issues |
| |
| None |
| |
| Revision History |
| |
| Rev. Date Author Changes |
| ---- -------- ---------- -------------------------------------------- |
| 1 08/13/19 Shrek Shao First revision. |
