To Aru Kagaku no Railgun [JAP] - ULJS00354

[Hykem]

I think the optimized reading is simply moving all the vertex data directly from memory into a buffer and passing that to the RE, bypassing actually reading the information into VertexInfo to speed up the process. Problem is, by never reading the actual position, we can't really implement a check on the z-value. This might be a quirk in the PSP's rendering that OpenGL doesn't have.

As of r2439 there's now the option to disable the optimized VertexInfo reading. Apparently, it's not only the Z value checking that can cause issues. The problem may be more complex and it seems to reside in the whole SDK these latest game developers have been using.
As a workaround, disabling the optimized reading is helping some games displaying graphics properly.