The bug

The texture displayed on screen when a player stands inside fire is hardcoded, rather than defined by the model of the block in question. This is inconsistent with nether portals, which use the particle parameter, and all blocks the player can suffocate in, which do much the same.

How to reproduce

1. Download and apply the attached resource pack
2. Stand inside of stone (using pistons, ender pearls, switching out of Spectator while underground, etc.)
3. Stand inside of a nether portal
4. Stand inside of fire

Expected results

In all three cases, you'd see the pink stained glass texture.

Actual results

You correctly see the texture when standing inside of stone or inside of a nether portal. However, the fire texture is still used when standing inside fire, which is incorrect.

How to fix

Make the fire overlay texture reference the fire block models rather than hardcoding it.