Add note on lack of signed equivalent of BC6
@@ -25,7 +25,7 @@ their compressed bitrate are shown in the table below.
| BC3nm | G+R | 8 | BC1 G + BC4 R |
| BC4 | R | 4 | L8 |
| BC5 | R+G | 8 | BC1 R + BC1 G |
-| BC6 | RGB (HDR) | 8 | |
+| BC6H | RGB (HDR) | 8 | |
| BC7 | RGB / RGBA | 8 | |
| EAC_R11 | R | 4 | R11 |
| EAC_RG11 | RG | 8 | RG11 |
@@ -105,7 +105,7 @@ use today.
| BC3nm | `gggr` | `.ag` | |
| BC4 | `rrr1` | `.r` | |
| BC5 | `rrrg` | `.ra` <sup>2</sup> | |
-| BC6 | `rgb1` | `.rgb` | HDR profile only |
+| BC6H | `rgb1` | `.rgb` <sup>3</sup> | HDR profile only |
| BC7 | `rgba` | `.rgba` | |
| EAC_R11 | `rrr1` | `.r` | |
| EAC_RG11 | `rrrg` | `.ra` <sup>2</sup> | |
@@ -125,6 +125,9 @@ be emulated by setting texture component swizzles in the runtime API - e.g. via
`glTexParameteri()` for OpenGL ES - although it has been noted that API
controlled swizzles are not available in WebGL.
+**3:** ASTC can only store unsigned values, and has no equivalent of the BC6
+signed endpoint mode.
+
# Other Considerations
This section outlines some of the other things to consider when encoding
