From 03aee7ddc9d932df9664da8e6f2cfc7080abaaa2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Crozet?= <developer@crozet.re>
Date: Sun, 26 Feb 2023 18:33:54 +0100
Subject: [PATCH] Fix collision-detection regression with convex polyhedron
 caused by the internal edges handling

---
 .../contact_manifolds/contact_manifolds_pfm_pfm.rs  | 13 +++++++++----
 src/shape/convex_polyhedron.rs                      |  4 ++++
 src/shape/polygonal_feature_map.rs                  |  7 +++++++
 3 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/src/query/contact_manifolds/contact_manifolds_pfm_pfm.rs b/src/query/contact_manifolds/contact_manifolds_pfm_pfm.rs
index 836ccf70..84731271 100644
--- a/src/query/contact_manifolds/contact_manifolds_pfm_pfm.rs
+++ b/src/query/contact_manifolds/contact_manifolds_pfm_pfm.rs
@@ -6,6 +6,7 @@ use crate::query::{
 };
 use crate::shape::{PackedFeatureId, PolygonalFeature, PolygonalFeatureMap, Shape};
 use na::Unit;
+use std::any::Any;
 
 /// Computes the contact manifold between two convex shapes implementing the `PolygonalSupportMap`
 /// trait, both represented as `Shape` trait-objects.
@@ -92,13 +93,17 @@ pub fn contact_manifold_pfm_pfm<'a, ManifoldData, ContactData, S1, S2>(
                 false,
             );
 
-            if manifold.points.is_empty() {
-                // cfg!(feature = "dim3") || (cfg!(feature = "dim2") && manifold.points.is_empty()) {
+            if (cfg!(feature = "dim2") && manifold.points.is_empty())
+                // TODO: this test is a workaround until we figure-out a way to
+                //       determine the feature ids for the GJK/EPA contact.
+                || pfm1.is_convex_polyhedron()
+                || pfm2.is_convex_polyhedron()
+            {
                 let contact = TrackedContact::new(
                     p1,
                     pos12.inverse_transform_point(&p2_1),
-                    PackedFeatureId::UNKNOWN, // FIXME: We don't know what features are involved.
-                    PackedFeatureId::UNKNOWN, // FIXME
+                    PackedFeatureId::UNKNOWN, // TODO: We don't know what features are involved.
+                    PackedFeatureId::UNKNOWN,
                     (p2_1 - p1).dot(&dir),
                 );
                 manifold.points.push(contact);
diff --git a/src/shape/convex_polyhedron.rs b/src/shape/convex_polyhedron.rs
index 948bce26..81c553a9 100644
--- a/src/shape/convex_polyhedron.rs
+++ b/src/shape/convex_polyhedron.rs
@@ -558,6 +558,10 @@ impl PolygonalFeatureMap for ConvexPolyhedron {
         out_feature.fid = PackedFeatureId::face(best_fid as u32);
         out_feature.num_vertices = num_vertices as usize;
     }
+
+    fn is_convex_polyhedron(&self) -> bool {
+        true
+    }
 }
 
 /*
diff --git a/src/shape/polygonal_feature_map.rs b/src/shape/polygonal_feature_map.rs
index 82cc7aad..f5ac81f2 100644
--- a/src/shape/polygonal_feature_map.rs
+++ b/src/shape/polygonal_feature_map.rs
@@ -17,6 +17,13 @@ use na::{ComplexField, RealField}; // for .abs() and .copysign()
 pub trait PolygonalFeatureMap: SupportMap {
     /// Compute the support polygonal face of `self` towards the `dir`.
     fn local_support_feature(&self, dir: &Unit<Vector<Real>>, out_feature: &mut PolygonalFeature);
+
+    // TODO: this is currently just a workaround for https://github.com/dimforge/rapier/issues/417
+    //       until we get a better way to deal with the issue without breaking internal edges
+    //       handling.
+    fn is_convex_polyhedron(&self) -> bool {
+        false
+    }
 }
 
 impl PolygonalFeatureMap for Segment {