glDrawArraysInstancedBaseInstance

glDrawArraysInstancedBaseInstance behaves identically to glDrawArrays except that instancecount 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:

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: $\frac{\mathrm{gl}\_\mathrm{InstanceID}}{\mathrm{divisor}}\mathrm{baseInstance}$ . Note that baseinstance does not affect the shader-visible value of gl_InstanceID .

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 instancecount is 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.

glDrawArrays , glDrawElementsInstanced

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