with OptiFine glass texture of the glass facades do not look transparent
Textures with zero transparency are displayed normally
OptiFine_1.12.2_HD_U_E1

• Minecraft Version: 1.12.2
• AE2 Version: appliedenergistics2-rv6-alpha-3
• Forge Version: 1.12.2-forge1.12.2-14.23.4.2705

Please report Optifine bugs to Optifine itself as it is closed source and we do not know it it changes/breaks the default vanilla/forge rendering.