glDrawArraysInstancedBaseInstance man page on RedHat
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GLDRAWARRAYSINSTANCE(3G) OpenGL Manual GLDRAWARRAYSINSTANCE(3G)
NAME
glDrawArraysInstancedBaseInstance - draw multiple instances of a range
of elements with offset applied to instanced attributes
C SPECIFICATION
void glDrawArraysInstancedBaseInstance(GLenum mode, GLint first,
GLsizei count,
GLsizei primcount,
GLuint baseinstance);
PARAMETERS
mode
Specifies what kind of primitives to render. Symbolic constants
GL_POINTS, GL_LINE_STRIP, GL_LINE_LOOP, GL_LINES,
GL_TRIANGLE_STRIP, GL_TRIANGLE_FAN, GL_TRIANGLES
GL_LINES_ADJACENCY, GL_LINE_STRIP_ADJACENCY,
GL_TRIANGLES_ADJACENCY, GL_TRIANGLE_STRIP_ADJACENCY and GL_PATCHES
are accepted.
first
Specifies the starting index in the enabled arrays.
count
Specifies the number of indices to be rendered.
primcount
Specifies the number of instances of the specified range of indices
to be rendered.
baseinstance
Specifies the base instance for use in fetching instanced vertex
attributes.
DESCRIPTION
glDrawArraysInstancedBaseInstance behaves identically to glDrawArrays()
except that primcount instances of the range of elements are executed
and the value of the internal counter instanceID advances for each
iteration. instanceID is an internal 32-bit integer counter that may
be read by a vertex shader as gl_InstanceID.
glDrawArraysInstancedBaseInstance has the same effect as:
if ( mode or count is invalid )
generate appropriate error
else {
for (int i = 0; i < primcount ; i++) {
instanceID = i;
glDrawArrays(mode, first, count);
}
instanceID = 0;
}
Specific vertex attributes may be classified as instanced through the
use of glVertexAttribDivisor(). Instanced vertex attributes supply
per-instance vertex data to the vertex shader. The index of the vertex
fetched from the enabled instanced vertex attribute arrays is
calculated as: gl _ InstanceID divisor + baseInstance. Note that
baseinstance does not affect the shader-visible value of gl_InstanceID.
ERRORS
GL_INVALID_ENUM is generated if mode is not one of the accepted values.
GL_INVALID_OPERATION is generated if a geometry shader is active and
mode is incompatible with the input primitive type of the geometry
shader in the currently installed program object.
GL_INVALID_VALUE is generated if count or primcount are negative.
GL_INVALID_OPERATION is generated if a non-zero buffer object name is
bound to an enabled array and the buffer object's data store is
currently mapped.
SEE ALSO
glDrawArrays(), glDrawElementsInstanced()
COPYRIGHT
Copyright © 2011 Khronos Group. This material may be distributed
subject to the terms and conditions set forth in the Open Publication
License, v 1.0, 8 June 1999. http://opencontent.org/openpub/.
AUTHORS
opengl.org
opengl.org 03/16/2013 GLDRAWARRAYSINSTANCE(3G)
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