Manpages OpenGL - glDrawElementsInstancedBaseVertexBaseInstance

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Name

glDrawElementsInstancedBaseVertexBaseInstance — render multiple instances of a set of primitives from array data with a per-element offset

C Specification

`void glDrawElementsInstancedBaseVertexBaseInstance(`	GLenum `mode`,
	GLsizei `count`,
	GLenum `type`,
	GLvoid *`indices`,
	GLsizei `primcount`,
	GLint `basevertex`,
	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.
count: Specifies the number of elements to be rendered.
type: Specifies the type of the values in indices. Must be one of GL_UNSIGNED_BYTE, GL_UNSIGNED_SHORT, or GL_UNSIGNED_INT.
indices: Specifies a pointer to the location where the indices are stored.
primcount: Specifies the number of instances of the indexed geometry that should be drawn.
basevertex: Specifies a constant that should be added to each element of indices when chosing elements from the enabled vertex arrays.
baseinstance: Specifies the base instance for use in fetching instanced vertex attributes.

Description

glDrawElementsInstancedBaseVertexBaseInstance behaves identically to glDrawElementsInstanced except that the ith element transferred by the corresponding draw call will be taken from element indices[i] + basevertex of each enabled array. If the resulting value is larger than the maximum value representable by type, it is as if the calculation were upconverted to 32-bit unsigned integers (with wrapping on overflow conditions). The operation is undefined if the sum would be negative. The basevertex has no effect on the shader-visible value of gl_VertexID.

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.

Notes

glDrawElementsInstancedBaseVertex is only supported if the GL version is 3.2 or greater.

Errors

GL_INVALID_ENUM is generated if mode is not an accepted value.

GL_INVALID_VALUE is generated if count or primcount is negative.

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_OPERATION is generated if a non-zero buffer object name is bound to an enabled array or the element array and the buffer object's data store is currently mapped.