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