update documentation to include h and v flip

yeastplume · Jun 15, 2020 · 9ed1107 · 9ed1107
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diff --git a/docs/ex_004.md b/docs/ex_004.md
@@ -53,6 +53,18 @@ And here's the result of assembling and poking all this data via the [tile_wall
 
  The end result in both the BASIC and Assembly versions are the same. The assembly version is nice and fast. The BASIC version reminds me of a Next Generation episode where Picard experienced an entire lifetime in about 15 minutes elapsed time. You should have time to go and do something similar while you wait for the BASIC version to finish doing its thing.
 
+## Horizontal and Vertical Flip
+
+The more astute among you may have noticed the poorly-drawn set of symbols in the Tilemap:
+
+![tile_wall tiles](images/04-tile_wall-006.png)
+
+However if you look at the Imageset, only the first symbol is present:
+
+![tile_wall tiles](images/04-tile_wall-007.png)
+
+Non-text VERA display modes allow a vertical-flip and horizontal-flip flag to be set for each tile in a Tilemap, and the four tiles in our Aloevera Tilemap .png contain the unflipped original tile, the vertically-flipped version, the horizontally-flipped, and both flipped frames respectively. Aloevera is clever enough to recognise when an input Tile is the flipped version of a frame in the Imageset, and if it encouters a flipped tile it will output the original sorce index as well as the correct v and h flip fields at assembly time.
+
 ## More on Palette Alignment
 
 For a bit of futher clarity of the alignment rules above, let's consider a brief example from one of Aloevera's automated tests. This is a 2 Frame Imageset targeted at 2BPP (4 Colour Mode). Thus, each tile in the Imageset consists of indices from a range of 4 colours, and each range must start on a multiple of 16:
@@ -83,6 +95,4 @@ There's still plenty of work and future possibilities for Aloevera's Tilemap sup
 
 * The ability to 'append' maps together to create larger maps to be used in scrolling applications.
 * A better method of specifying the foreground and background colours for each tile in Text_16 mode.
-* 'Conflating' Tilemaps, essentially blowing Tilemap data to be the size of the target VERA map size.
-* Support for Tile rotation
 * Output assembly code that does the Tilemap loading
diff --git a/docs/images/04-tile_wall-001.png b/docs/images/04-tile_wall-001.png
diff --git a/docs/images/04-tile_wall-002.png b/docs/images/04-tile_wall-002.png
diff --git a/docs/images/04-tile_wall-003.png b/docs/images/04-tile_wall-003.png
diff --git a/docs/images/04-tile_wall-006.png b/docs/images/04-tile_wall-006.png
diff --git a/docs/images/04-tile_wall-007.png b/docs/images/04-tile_wall-007.png