From 546c43b9cc7b147e4127acddf9bde9e12190cf64 Mon Sep 17 00:00:00 2001 From: Patrick Owen Date: Sun, 21 May 2023 12:48:51 -0400 Subject: [PATCH] Add logic to prevent slanted walls from lifting the player up --- common/src/character_controller/mod.rs | 68 ++++++++++++++++--- .../src/character_controller/vector_bounds.rs | 44 ++++++++++-- 2 files changed, 97 insertions(+), 15 deletions(-) diff --git a/common/src/character_controller/mod.rs b/common/src/character_controller/mod.rs index 86106c49..84802c8a 100644 --- a/common/src/character_controller/mod.rs +++ b/common/src/character_controller/mod.rs @@ -1,6 +1,8 @@ mod collision; mod vector_bounds; +use std::mem::replace; + use tracing::warn; use crate::{ @@ -144,6 +146,7 @@ fn get_ground_normal( } bounds.apply_and_add_bound( VectorBound::new_push(collision.normal, collision.normal), + &[], &mut allowed_displacement, None, ); @@ -219,11 +222,14 @@ fn apply_velocity( let mut remaining_dt_seconds = ctx.dt_seconds; - let mut velocity_info = VelocityInfo { + let initial_velocity_info = VelocityInfo { bounds: VectorBoundGroup::new(&average_velocity), average_velocity, final_velocity: *velocity, }; + let mut velocity_info = initial_velocity_info.clone(); + + let mut ground_collision_handled = false; let mut all_collisions_resolved = false; for _ in 0..MAX_COLLISION_ITERATIONS { @@ -239,7 +245,14 @@ fn apply_velocity( - collision_result.displacement_vector.magnitude() / expected_displacement.magnitude(); - handle_collision(ctx, collision, &mut velocity_info, ground_normal); + handle_collision( + ctx, + collision, + &initial_velocity_info, + &mut velocity_info, + ground_normal, + &mut ground_collision_handled, + ); } else { all_collisions_resolved = true; break; @@ -257,23 +270,62 @@ fn apply_velocity( fn handle_collision( ctx: &CharacterControllerContext, collision: Collision, + initial_velocity_info: &VelocityInfo, velocity_info: &mut VelocityInfo, ground_normal: &mut Option>, + ground_collision_handled: &mut bool, ) { // Collisions are divided into two categories: Ground collisions and wall collisions. // Ground collisions will only affect vertical movement of the character, while wall collisions will - // push the character away from the wall in a perpendicular direction. + // push the character away from the wall in a perpendicular direction. If the character is on the ground, + // we have extra logic to ensure that slanted wall collisions do not lift the character off the ground. if is_ground(ctx, &collision.normal) { - velocity_info.bounds.apply_and_add_bound( - VectorBound::new_push(collision.normal, ctx.up), - &mut velocity_info.average_velocity, - Some(&mut velocity_info.final_velocity), - ); + let stay_on_ground_bounds = [VectorBound::new_pull(collision.normal, ctx.up)]; + if !*ground_collision_handled { + // Wall collisions can turn vertical momentum into unwanted horizontal momentum. This can + // occur if the character jumps at the corner between the ground and a slanted wall. If the wall + // collision is handled first, this horizontal momentum will push the character away from the wall. + // This can also occur if the character is on the ground and walks into a slanted wall. A single frame + // of downward momentum caused by gravity can turn into unwanted horizontal momentum that pushes + // the character away from the wall. Neither of these issues can occur if the ground collision is + // handled first, so when computing how the velocity vectors change, we rewrite history as if + // the ground collision was first. This is only necessary for the first ground collision, since + // afterwards, there is no more unexpected vertical momentum. + let old_velocity_info = replace(velocity_info, initial_velocity_info.clone()); + velocity_info.bounds.apply_and_add_bound( + VectorBound::new_push(collision.normal, ctx.up), + &stay_on_ground_bounds, + &mut velocity_info.average_velocity, + Some(&mut velocity_info.final_velocity), + ); + for bound in old_velocity_info.bounds.bounds() { + velocity_info.bounds.apply_and_add_bound( + bound.clone(), + &stay_on_ground_bounds, + &mut velocity_info.average_velocity, + Some(&mut velocity_info.final_velocity), + ); + } + + *ground_collision_handled = true; + } else { + velocity_info.bounds.apply_and_add_bound( + VectorBound::new_push(collision.normal, ctx.up), + &stay_on_ground_bounds, + &mut velocity_info.average_velocity, + Some(&mut velocity_info.final_velocity), + ); + } *ground_normal = Some(collision.normal); } else { + let mut stay_on_ground_bounds = Vec::new(); + if let Some(ground_normal) = ground_normal { + stay_on_ground_bounds.push(VectorBound::new_pull(*ground_normal, ctx.up)); + } velocity_info.bounds.apply_and_add_bound( VectorBound::new_push(collision.normal, collision.normal), + &stay_on_ground_bounds, &mut velocity_info.average_velocity, Some(&mut velocity_info.final_velocity), ); diff --git a/common/src/character_controller/vector_bounds.rs b/common/src/character_controller/vector_bounds.rs index 20feeea8..03529f1f 100644 --- a/common/src/character_controller/vector_bounds.rs +++ b/common/src/character_controller/vector_bounds.rs @@ -27,16 +27,22 @@ impl VectorBoundGroup { } } - /// Constrains `vector` with `new_bound` while keeping the existing constraints satisfied. - /// All projection transformations applied to `vector` are also applied + /// Returns the internal list of `VectorBound`s contained in the `VectorBoundGroup` struct. + pub fn bounds(&self) -> &[VectorBound] { + &self.bounds + } + + /// Constrains `vector` with `new_bound` while keeping the existing constraints and any constraints in + /// `temporary_bounds` satisfied. All projection transformations applied to `vector` are also applied /// to `tagalong` to allow two vectors to be transformed consistently with each other. pub fn apply_and_add_bound( &mut self, new_bound: VectorBound, + temporary_bounds: &[VectorBound], vector: &mut na::Vector3, tagalong: Option<&mut na::Vector3>, ) { - self.apply_bound(&new_bound, vector, tagalong); + self.apply_bound(&new_bound, temporary_bounds, vector, tagalong); self.bounds.push(new_bound); } @@ -44,6 +50,7 @@ impl VectorBoundGroup { fn apply_bound( &self, new_bound: &VectorBound, + temporary_bounds: &[VectorBound], vector: &mut na::Vector3, mut tagalong: Option<&mut na::Vector3>, ) { @@ -55,6 +62,9 @@ impl VectorBoundGroup { // bound that allows all bounds to be satisfied, and (3) zero out the vector if no such pairing works, as we // assume that we need to apply three linearly independent bounds. + // Combine existing bounds with temporary bounds into an iterator + let bounds_iter = self.bounds.iter().chain(temporary_bounds.iter()); + // Apply new_bound if necessary. if !new_bound.check_vector(vector, self.error_margin) { new_bound.constrain_vector(vector, self.error_margin); @@ -65,13 +75,13 @@ impl VectorBoundGroup { } // Check if all constraints are satisfied - if (self.bounds.iter()).all(|b| b.check_vector(vector, self.error_margin)) { + if (bounds_iter.clone()).all(|b| b.check_vector(vector, self.error_margin)) { return; } // If not all constraints are satisfied, find the first constraint that if applied will satisfy // the remaining constriants - for bound in (self.bounds.iter()).filter(|b| !b.check_vector(vector, self.error_margin)) { + for bound in (bounds_iter.clone()).filter(|b| !b.check_vector(vector, self.error_margin)) { let Some(ortho_bound) = bound.get_self_constrained_with_bound(new_bound) else { warn!("Unsatisfied existing bound is parallel to new bound. Is the character squeezed between two walls?"); @@ -81,7 +91,7 @@ impl VectorBoundGroup { let mut candidate = *vector; ortho_bound.constrain_vector(&mut candidate, self.error_margin); - if (self.bounds.iter()).all(|b| b.check_vector(&candidate, self.error_margin)) { + if (bounds_iter.clone()).all(|b| b.check_vector(&candidate, self.error_margin)) { *vector = candidate; if let Some(ref mut tagalong) = tagalong { ortho_bound.constrain_vector(tagalong, 0.0); @@ -124,6 +134,22 @@ impl VectorBound { } } + /// Creates a `VectorBound` that pulls vectors towards the plane given + /// by the normal in `projection_direction`. Even after applying such a bound to + /// a vector, its dot product with `normal` should still be positive even counting + /// floating point approximation limitations. This ensures that `new_push` and + /// `new_pull` don't conflict with each other even with equal parameters. + pub fn new_pull( + normal: na::UnitVector3, + projection_direction: na::UnitVector3, + ) -> Self { + VectorBound { + normal: na::UnitVector3::new_unchecked(-normal.as_ref()), + projection_direction, + error_margin_factor: -1.0, + } + } + /// Updates `subject` with a projection transformation based on the constraint given by `self`. /// This function does not check whether such a constraint is needed. fn constrain_vector(&self, subject: &mut na::Vector3, error_margin: f32) { @@ -183,6 +209,7 @@ mod tests { // Add a bunch of bounds that are achievable with nonzero vectors bounds.apply_and_add_bound( VectorBound::new_push(unit_vector(1.0, 3.0, 4.0), unit_vector(1.0, 2.0, 2.0)), + &[], &mut constrained_vector, None, ); @@ -192,6 +219,7 @@ mod tests { bounds.apply_and_add_bound( VectorBound::new_push(unit_vector(2.0, -3.0, -4.0), unit_vector(1.0, -2.0, -1.0)), + &[], &mut constrained_vector, None, ); @@ -201,6 +229,7 @@ mod tests { bounds.apply_and_add_bound( VectorBound::new_push(unit_vector(2.0, -3.0, -5.0), unit_vector(1.0, -2.0, -2.0)), + &[], &mut constrained_vector, None, ); @@ -211,6 +240,7 @@ mod tests { // Finally, add a bound that overconstrains the system bounds.apply_and_add_bound( VectorBound::new_push(unit_vector(-3.0, 3.0, -2.0), unit_vector(-3.0, 3.0, -2.0)), + &[], &mut constrained_vector, None, ); @@ -278,7 +308,7 @@ mod tests { } fn assert_bounds_achieved(bounds: &VectorBoundGroup, subject: &na::Vector3) { - for bound in &bounds.bounds { + for bound in bounds.bounds() { assert!(bound.check_vector(subject, bounds.error_margin)); } }