Pause doc: Pages drawing (#2190)

* name main fields and regs for pages drawing

* comments

* format

* more comments

* roll -> pitch (oops)

* Document `PauseContext.offsetY`, `R_PAUSE_OFFSET_VERTICAL` as "y origin 1/2"

* copypaste comment on page pitches fields

* "offset depth" -> "depth offset"

* review

2 files changed, 14 insertions, 7 deletions

diff --git a/include/regs.h b/include/regs.h
index 8abc2e3f0..b5c39ea63 100644
--- a/include/regs.h
+++ b/include/regs.h
@@ -183,6 +183,8 @@
 #define R_ROOM_CULL_USED_ENTRIES                 iREG(88)
 #define R_ROOM_CULL_DEBUG_TARGET                 iREG(89)
 #define R_B_LABEL_DD                             WREG(0)
+#define R_PAUSE_PAGES_Y_ORIGIN_2                 WREG(2) // Complements PauseContext.pagesYOrigin1
+#define R_PAUSE_DEPTH_OFFSET                     WREG(3) // Offset position of all pages away from the camera
 #if OOT_NTSC
 #define R_B_LABEL_SCALE(i)                       WREG(8 + (i))
 #define R_B_LABEL_X(i)                           WREG(10 + (i))
diff --git a/include/z64pause.h b/include/z64pause.h
index c9485a1e2..4f17e7031 100644
--- a/include/z64pause.h
+++ b/include/z64pause.h
@@ -141,6 +141,11 @@ typedef enum WorldMapPointState {
     /* 2 */ WORLD_MAP_POINT_STATE_HIGHLIGHT
 } WorldMapPointState;
 
+// Values for PauseContext.pagesYOrigin1 and R_PAUSE_PAGES_Y_ORIGIN_2 respectively,
+// that make the pause pages rotate around their lower edge instead of the middle.
+#define PAUSE_PAGES_Y_ORIGIN_1_LOWER 80 // PAGE_BG_ROWS * PAGE_BG_QUAD_HEIGHT / 2
+#define PAUSE_PAGES_Y_ORIGIN_2_LOWER (s16)(-PAUSE_PAGES_Y_ORIGIN_1_LOWER * 0.78 * 100)
+
 typedef struct PauseContext {
     /* 0x0000 */ View view;
     /* 0x0128 */ u8* iconItemSegment;
@@ -174,14 +179,14 @@ typedef struct PauseContext {
     /* 0x01E8 */ u16 pageIndex; // "kscp_pos"
     /* 0x01EA */ u16 pageSwitchTimer;
     /* 0x01EC */ u16 savePromptState;
-    /* 0x01F0 */ f32 unk_1F0;
-    /* 0x01F4 */ f32 unk_1F4;
-    /* 0x01F8 */ f32 unk_1F8;
-    /* 0x01FC */ f32 unk_1FC;
-    /* 0x0200 */ f32 unk_200;
-    /* 0x0204 */ f32 unk_204; // "angle_s"
+    /* 0x01F0 */ f32 promptDepthOffset; // Offset position of the prompt away from the camera
+    /* 0x01F4 */ f32 itemPagePitch; // Rotation of the item page around its local horizontal/sideways axis
+    /* 0x01F8 */ f32 equipPagePitch; // Rotation of the equip page around its local horizontal/sideways axis
+    /* 0x01FC */ f32 mapPagePitch; // Rotation of the map page around its local horizontal/sideways axis
+    /* 0x0200 */ f32 questPagePitch; // Rotation of the quest page around its local horizontal/sideways axis
+    /* 0x0204 */ f32 promptPitch; // Rotation of the prompt around its local horizontal/sideways axis. "angle_s"
     /* 0x0208 */ u16 alpha;
-    /* 0x020A */ s16 offsetY;
+    /* 0x020A */ s16 pagesYOrigin1;
     /* 0x020C */ char unk_20C[0x08];
     /* 0x0214 */ s16 stickAdjX;
     /* 0x0216 */ s16 stickAdjY;