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Alpha blending issues on some platforms
02-07-2015, 03:17 PM
Post: #1
Exclamation Alpha blending issues on some platforms
I am trying to get ppssppsdl to run on several ARM linux platforms.

1) using Mali fbdev drivers and my own SDL2 video context driver (and slightly modified init code in PCMain.cpp), I can get it to run on Odroid C1 (Mali450) and Odroid U3 (Mali 400). On Odroid-C1 however there are issues with alpha blending, the transparent textures including the moving bits in the PPSSPPSDL menu have a black background. The same build works well on U3. Apparently the amlogic in C1 does alpha blending internally - and this might be the issue. Reducing the depth from 32bpp to 16bpp (which cannot be done on the fly, it's a boot parameter of the board) solves the issue for C1 as well - but can I somehow make this work with 32bpp as well?

2) same issue on a PowerVR422MP2 (Odroid XU), using libhybris to have GLES2 from its android driver. I did a similar procedure there, my own SDL2 video context driver and slightly modified init code in PCMain.cpp. There is an issue with libhybris (does not allow ppsspp to create an egl_surface after sdl2 took over, so I am getting the egl_surface created by SDL2 using something like (wiki.libsdl.org/SDL_SysWMinfo) for SDL_SYSWM_ANDROID - I am getting both the native window and the egl_surface from SDL2). Again, things work except for the alpha blending Sad

All of them (including C1 in 32bpp, PowerVR) do not have this issue when using the libretro core... so i'm guessing it must be something which is set up from SDL init... I've tried setting up SDL2 with PIXEL_FORMAT RGB888 instead of RGBA8888, I tried setting in PCMain.cpp (github.com/hrydgard/native/blob/master/base/PCMain.cpp#L442) ALPHA 8 (it's currently setting only RGB) and several other combinations or similar things ... nothing worked Sad

Any ideas?

PS - also, the PVR422MP2 performance was similar (or worse) than Mali400, which makes no sense to me, as performance should be x2 for PVR... any ideas why?
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Alpha blending issues on some platforms - memeka - 02-07-2015 03:17 PM

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