glDrawArraysInstancedGLenum

glDrawArraysIndirect is a function in the OpenGL API used for drawing primitives. It allows for a more efficient way to issue multiple draw calls by providing an array of structures containing drawing parameters. Instead of making individual glDrawArrays or glDrawElements calls for each set of primitives, a single glDrawArraysIndirect call can be made with a buffer containing all the necessary information.

This function takes a pointer to a buffer object that holds a structure, or an array of structures, containing the arguments for one or more glDrawArrays calls. Each structure typically includes the count of vertices to be rendered, the primitive type (e.g., GL_TRIANGLES, GL_LINES), the starting index of the vertex data, and potentially other offsets.

The primary benefit of using glDrawArraysIndirect is performance. By reducing the number of API calls and allowing the GPU to fetch drawing parameters directly from memory, it can significantly decrease CPU overhead, especially when rendering many small sets of primitives. This is particularly useful in scenarios like particle systems, instanced rendering, or rendering a large number of independent objects.

To use glDrawArraysIndirect, an application first binds a buffer object using glBindBuffer. This buffer is then populated with the indirect draw command structures. Finally, glDrawArraysIndirect is called, referencing the bound buffer and the number of indirect draw commands to execute. This streamlined approach helps optimize rendering pipelines.