Update ARB_texture_compression_bptc.txt (#322)
diff --git a/extensions/ARB/ARB_texture_compression_bptc.txt b/extensions/ARB/ARB_texture_compression_bptc.txt
index e8c358c..8aab363 100644
--- a/extensions/ARB/ARB_texture_compression_bptc.txt
+++ b/extensions/ARB/ARB_texture_compression_bptc.txt
@@ -46,8 +46,8 @@
Version
- Last Modified Date: June 6, 2016
- Revision: 8
+ Last Modified Date: October 30, 2019
+ Revision: 9
Number
@@ -369,15 +369,16 @@
subset, then green and blue stored similarly. If a block has non-zero
alpha bits, the alpha data follows the color data with the same
organization. If not, alpha is overridden to 1.0. These bits are treated
- as the high bits of a fixed-point value in a byte. If the format has a
- shared P-bit, there are two bits for endpoints 0 and 1 from low to
- high. If the format has a per-endpoint P-bits, then there are 2*subsets
- P-bits stored in the same order as color and alpha. Both kinds of P-bits
- are added as a bit below the color data stored in the byte. So, for a
- format with 5 red bits, the P-bit ends up in bit 2. For final scaling, the
- top bits of the value are replicated into any remaining bits in the
- byte. For the preceding example, bits 6 and 7 would be written to bits 0
- and 1.
+ as the high bits of a fixed-point value in a byte. If the format has
+ shared P-bits, there are two endpoint bits, the lower of which applies to
+ both endpoints of subset 0 and the upper of which applies to both
+ endpoints of subset 1. If the format has a per-endpoint P-bits, then there
+ are 2*subsets P-bits stored in the same order as color and alpha. Both
+ kinds of P-bits are added as a bit below the color data stored in the
+ byte. So, for a format with 5 red bits, the P-bit ends up in bit 2. For
+ final scaling, the top bits of the value are replicated into any remaining
+ bits in the byte. For the preceding example, bits 6 and 7 would be written
+ to bits 0 and 1.
The endpoint colors are interpolated using index values stored in the
block. The index bits are stored in x-major order. Each index has the
@@ -893,6 +894,9 @@
Rev. Date Author Changes
---- -------- ----------- --------------------------------------------
+ 9 30/10/19 pdaniell Fix shared p-bits specification to match
+ DX and the Khronos Data Format spec.
+
8 06/06/16 Nanley Chery Reduce the requirements to the minimal set.
7 01/20/11 pbrown Change the base internal format of the floating-
