For both, you pass OpenGL some buffers containing vertex data.
glDrawArrays is basically "draw this contiguous range of vertices, using the data I gave you earlier". Good:
You don't need to build an index buffer
Bad:
If you organise your data into GL_TRIANGLES, you will have duplicate vertex data for adjacent triangles. This is obviously wasteful.
If you use GL_TRIANGLE_STRIP and GL_TRIANGLE_FAN to try and avoid duplicating data: it isn't terribly effective and you'd have to make a rendering call for each strip and fan. OpenGL calls are expensive and should be avoided where possible
With glDrawElements, you pass in buffer containing the indices of the vertices you want to draw.
Good
No duplicate vertex data - you just index the same data for different triangles
You can just use GL_TRIANGLES and rely on the vertex cache to avoid processing the same data twice - no need to re-organise your geometry data or split rendering over multiple calls
Bad
Memory overhead of index buffer
My recommendation is to use glDrawElements
个人理解为:
glDrawArrays主要讲数据空间损耗在顶点的定义处;
glDrawElements主要讲数据空间损耗在顶点索引的定义处;
如果在你的工程中，画的图形较少或者，图形虽多但很多相同的，则可采用glDrawArrays更节省数据占用的空间；
相反，如果图形多，而且形状大不相同的时候，可以优先考虑采用glDrawElements函数。
(点击上面的名称，即可进入官方对此函数的说明)
本文博客源地址:http://blog.csdn.net/ypist