I know this thread is a little old, but it's the best one I could find on the internet explaining anything.
I can't seem to get RetroArch to load the textures.
I have followed the setup, even got PJ64 to create the .htc files (and tried the .htc ones from the post for MM and OOT)
I am on RetroArch version 1.6.7 using the Mupen64Plus OpenGL 2.5 d1451bb core that I downloaded form the "online updater" thing in RA.
I changed the core settings in the file "retroarch\retroarch-core-options.cfg" where i found the options:
mupen64plus-txHiresEnable = "true"
mupen64plus-txHiresFullAlphaChannel = "true"
I have the htc file in "RetroArch\system\Mupen64plus\cache\FILE FROM PJ64_HIRESTEXTURES.htc"
What on earth am I missing here. Did they add support for this, then immediately take it away less than a year later?