Here I am sharing my experience with openGL ES 2 on MeeGo 1.2
(hardware with CPU: ATOM N450/N455):
1. It is slow.
The same machine can render much higher triangles on Windows (with DX8/DX9).
2. Vertex count matters a lot.
It is not triangle count but vertex count that matters most. I guess this is due to hardware pixel shader and software vertex shader.
The vertex shader processing is very slow.
3. Performance degrades a lot when mesh is stored in RAM instead of OpenGL Buffer Object.
The openGL ES example available stores geometry in RAM which is not a fast way.
Quality:
1. The triangles are not perspective correct. That means when you see big near polygons the texture gets distorted.
The distortion is high when the the polygons gets half clipped.
Please note that this happens only when a perspective matrix is applied (which is not the case of spinning cube example).
OpenGL ES 2 even do not have any switch for perspective correction, because it assumes everything should be perspective correct.
This is problem is of vertex processing and not the hardware (because same hardware does perspective correction on Windows).
This problem forces us to tesselate the geometry but then vertex count increases and performance degrades.
It will be difficult to develop/port 3D games to MeeGo in this situation.
If the MeeGo openGL developers are listening please give it a high priority.
MeeGo OpenGL ES 2: Performance and quality
mar, 26/07/2011 - 14:00
