[Android開發學習16]Android OpenGL ES 關於glDrawArrays和glDrawElements

 引用一段網上的話:

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

個人理解為:
glDrawArrays主要講數據空間損耗在頂點的定義處;
glDrawElements主要講數據空間損耗在頂點索引的定義處;
如果在你的工程中，畫的圖形較少或者，圖形雖多但很多相同的，則可采用glDrawArrays更節省數據占用的空間；
相反，如果圖形多，而且形狀大不相同的時候，可以優先考慮采用glDrawElements函數。
(點擊上面的名稱，即可進入官方對此函數的說明)