From 71d089c78495e43e4a68ae6aecc771f91838b374 Mon Sep 17 00:00:00 2001
From: griffi-gh <prasol258@gmail.com>
Date: Wed, 14 Feb 2024 01:59:37 +0100
Subject: [PATCH] wip client physics

---
 kubi/src/client_physics.rs | 75 +++++++++++++++++++++++++++++++++++---
 1 file changed, 69 insertions(+), 6 deletions(-)

diff --git a/kubi/src/client_physics.rs b/kubi/src/client_physics.rs
index cacbaf1..17bcb7b 100644
--- a/kubi/src/client_physics.rs
+++ b/kubi/src/client_physics.rs
@@ -1,9 +1,9 @@
 //TODO client-side physics
 //TODO move this to shared
-use glam::{Mat4, Vec3};
-use kubi_shared::transform::Transform;
+use glam::{vec3, IVec3, Mat4, Vec3};
 use shipyard::{track, AllStoragesView, Component, IntoIter, Unique, UniqueView, View, ViewMut};
-use crate::delta_time::DeltaTime;
+use kubi_shared::{block::{Block, CollisionType}, transform::Transform};
+use crate::{delta_time::DeltaTime, world::ChunkStorage};
 
 #[derive(Unique)]
 pub struct GlobalClPhysicsConfig {
@@ -12,20 +12,35 @@ pub struct GlobalClPhysicsConfig {
 
 #[derive(Component)]
 pub struct ClPhysicsActor {
+  pub offset: Vec3,
   pub forces: Vec3,
   pub velocity: Vec3,
   pub terminal_velocity: f32,
   //TODO: this should be configurable per block
   pub friction_agains_ground: f32,
+  on_ground_flag: bool,
+}
+
+impl ClPhysicsActor {
+  pub fn apply_force(&mut self, force: Vec3) {
+    self.forces += force;
+  }
+
+  pub fn on_ground(&self) -> bool {
+    self.on_ground_flag
+  }
 }
 
 impl Default for ClPhysicsActor {
   fn default() -> Self {
     Self {
+      //HACK: for player
+      offset: vec3(0., 1.5, 0.),
       forces: Vec3::ZERO,
       velocity: Vec3::ZERO,
       terminal_velocity: 40.,
       friction_agains_ground: 0.5,
+      on_ground_flag: false,
     }
   }
 }
@@ -34,16 +49,64 @@ pub fn init_client_physics(
   storages: AllStoragesView,
 ) {
   storages.add_unique(GlobalClPhysicsConfig {
-    gravity: Vec3::new(0., -9.8, 0.),
+    gravity: Vec3::new(0., -1.0, 0.),
   });
 }
 
 pub fn update_client_physics_late(
-  controllers: View<ClPhysicsActor>,
+  mut actors: ViewMut<ClPhysicsActor>,
   mut transforms: ViewMut<Transform, track::All>,
-  dt: UniqueView<DeltaTime>,
   phy_conf: UniqueView<GlobalClPhysicsConfig>,
+  world: UniqueView<ChunkStorage>,
+  dt: UniqueView<DeltaTime>,
 ) {
+  for (mut actor, mut transform) in (&mut actors, &mut transforms).iter() {
+    //apply forces
+    let actor_forces = actor.forces;
+    actor.velocity += actor_forces + phy_conf.gravity;
+    actor.forces = Vec3::ZERO;
+
+    let (scale, rotation, mut actor_position) = transform.0.to_scale_rotation_translation();
+    actor_position -= actor.offset;
+    let actor_block_pos = actor_position.floor().as_ivec3();
+    let actor_block = world.get_block(actor_block_pos);
+    let actor_block_below = world.get_block(actor_block_pos + IVec3::NEG_Y);
+    actor.on_ground_flag =
+      actor_block_below.map_or_else(|| false, |x| x.descriptor().collision == CollisionType::Solid) ||
+      actor_block.map_or_else(|| false, |x| x.descriptor().collision == CollisionType::Solid);
+    //push actor back out of the block
+    if actor_block.is_some() {
+      //first, compute the normal (assuming actor is a point)
+      //must be accurate!
+      let mut normal = Vec3::ZERO;
+      for i in 0..3 {
+        let mut offset = Vec3::ZERO;
+        offset[i] = 0.5;
+        let block_pos = actor_block_pos + offset.as_ivec3();
+        let block = world.get_block(block_pos).unwrap_or(Block::Air);
+        if block.descriptor().collision == CollisionType::Solid {
+          normal[i] = 1.;
+        }
+      }
+      //then, based on normal:
+      //push the actor back
+      actor_position += normal * 0.5;
+      //cancel out velocity in the direction of the normal
+      // let dot = actor.velocity.dot(normal);
+      // if dot > 0. {
+      //   //actor.velocity -= normal * dot;
+      //   actor.velocity = Vec3::ZERO;
+      // }
+      if actor.on_ground_flag {
+        actor.velocity.y = 0.;
+      }
+    }
+    //Apply velocity
+    actor_position += actor.velocity * dt.0.as_secs_f32();
+    actor_position += actor.offset;
+    transform.0 = Mat4::from_scale_rotation_translation(scale, rotation, actor_position);
+  }
+
   // for (_, mut transform) in (&controllers, &mut transforms).iter() {
   //   let (scale, rotation, mut translation) = transform.0.to_scale_rotation_translation();
   //   translation.y -= dt.0.as_secs_f32() * 100.;