From 611b55b2790d75bf9c706c1f5dca577f6ada253f Mon Sep 17 00:00:00 2001
From: Christof Petig <christof.petig@arcor.de>
Date: Fri, 15 Dec 2023 17:27:15 +0100
Subject: [PATCH] PRNG experiments

---
 voxygen/src/scene/terrain.rs  | 16 ++++++++++++++--
 world/src/site2/plot/house.rs | 27 +++++++++++++++++++--------
 2 files changed, 33 insertions(+), 10 deletions(-)

diff --git a/voxygen/src/scene/terrain.rs b/voxygen/src/scene/terrain.rs
index 7a7ebd0a00..720edd1686 100644
--- a/voxygen/src/scene/terrain.rs
+++ b/voxygen/src/scene/terrain.rs
@@ -270,9 +270,21 @@ pub fn get_sprite_instances<'a, I: 'a>(
             .overflowing_add((wpos.x as u64).overflowing_mul(wpos.y as u64).0)
             .0; // Awful PRNG
 
-        let ori = (block.get_ori().unwrap_or((seed % 4) as u8 * 2)) & 0b111;
+        // % 4 is non uniform, take 7 and combine two where >0
+        let ori = (block.get_ori().unwrap_or((((seed % 7) + 1) / 2) as u8 * 2)) & 0b111;
         if !cfg.variations.is_empty() {
-            let variation = seed as usize % cfg.variations.len();
+            let variation = match cfg.variations.len() {
+                // try to make the variation more uniform as the PRNG is unfair
+                1 => 0,
+                2 => (seed as usize % 4) / 3,
+                3 => (seed as usize % 5) / 2,
+                4 => ((seed as usize % 7) + 1) / 2,
+                _ => seed as usize % cfg.variations.len(),
+            };
+            //            let variation = seed as usize % cfg.variations.len();
+            if sprite == SpriteKind::ChristmasOrnament {
+                println!("{sprite:?} {variation} {wpos:?} {seed}");
+            }
             let key = (sprite, variation);
 
             // NOTE: Safe because we called sprite_config_for already.
diff --git a/world/src/site2/plot/house.rs b/world/src/site2/plot/house.rs
index cf6594bb0c..4d126cad2f 100644
--- a/world/src/site2/plot/house.rs
+++ b/world/src/site2/plot/house.rs
@@ -2225,32 +2225,43 @@ impl Structure for House {
             Fill::Block(Block::air(SpriteKind::Door).with_ori(door2_ori).unwrap()),
         );
         if self.christmas_decorations {
+            // we need to randomize position to see both variants
+            let rng = RandomField::new(0).get(self.door_tile.with_z(alt + 3));
+            let right = (rng % 2) as i32;
             let (door_light_pos, door_light_ori) = match self.front {
                 0 => (
                     Aabb {
-                        min: Vec2::new(self.door_tile.x, self.bounds.max.y + 1).with_z(alt + 3),
-                        max: Vec2::new(self.door_tile.x + 1, self.bounds.max.y + 2).with_z(alt + 4),
+                        min: Vec2::new(self.door_tile.x + right, self.bounds.max.y + 1)
+                            .with_z(alt + 3),
+                        max: Vec2::new(self.door_tile.x + 1 + right, self.bounds.max.y + 2)
+                            .with_z(alt + 4),
                     },
                     4,
                 ),
                 1 => (
                     Aabb {
-                        min: Vec2::new(self.bounds.max.x + 1, self.door_tile.y).with_z(alt + 3),
-                        max: Vec2::new(self.bounds.max.x + 2, self.door_tile.y + 1).with_z(alt + 4),
+                        min: Vec2::new(self.bounds.max.x + 1, self.door_tile.y + right)
+                            .with_z(alt + 3),
+                        max: Vec2::new(self.bounds.max.x + 2, self.door_tile.y + 1 + right)
+                            .with_z(alt + 4),
                     },
                     2,
                 ),
                 2 => (
                     Aabb {
-                        min: Vec2::new(self.door_tile.x, self.bounds.min.y - 1).with_z(alt + 3),
-                        max: Vec2::new(self.door_tile.x + 1, self.bounds.min.y).with_z(alt + 4),
+                        min: Vec2::new(self.door_tile.x + right, self.bounds.min.y - 1)
+                            .with_z(alt + 3),
+                        max: Vec2::new(self.door_tile.x + 1 + right, self.bounds.min.y)
+                            .with_z(alt + 4),
                     },
                     0,
                 ),
                 _ => (
                     Aabb {
-                        min: Vec2::new(self.bounds.min.x - 1, self.door_tile.y).with_z(alt + 3),
-                        max: Vec2::new(self.bounds.min.x, self.door_tile.y + 1).with_z(alt + 4),
+                        min: Vec2::new(self.bounds.min.x - 1, self.door_tile.y + right)
+                            .with_z(alt + 3),
+                        max: Vec2::new(self.bounds.min.x, self.door_tile.y + 1 + right)
+                            .with_z(alt + 4),
                     },
                     6,
                 ),