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[Godot Physics]: Correct typo in moment of inertia calculations. 

The moment of inertia calculation for BoxShape is:

```
Vector3(
    (p_mass / 3.0) * (ly * ly + lz * lz), 
    (p_mass / 3.0) * (lx * lx + lz * lz), 
    (p_mass / 3.0) * (lx * lx + ly * ly));
```

where the final line includes both the x and y extents.

However, for CapsuleShape3D, CylinderShape3D, ConvexPolygonShape3D, ConcavePolygonShape3D, and HeightMapShape3D, the final line read `(p_mass / 3.0) * (extents.y * extents.y + extents.y * extents.y)`.  I believe this is a mistake, considering the comment in each case mentions using an AABB approximation, which should follow the same approach as BoxShape.

This change corrects the final line to include both the x and y components of the shape's extent.
This commit is contained in:
Josh Jones 2021-03-22 20:10:11 -07:00
parent 0339200972
commit 9aadd0cde7
1 changed files with 5 additions and 5 deletions
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10
servers/physics_3d/shape_3d_sw.cpp
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@ -627,7 +627,7 @@ Vector3 CapsuleShape3DSW::get_moment_of_inertia(real_t p_mass) const {
return Vector3( return Vector3(
(p_mass / 3.0) * (extents.y * extents.y + extents.z * extents.z), (p_mass / 3.0) * (extents.y * extents.y + extents.z * extents.z),
(p_mass / 3.0) * (extents.x * extents.x + extents.z * extents.z), (p_mass / 3.0) * (extents.x * extents.x + extents.z * extents.z),
(p_mass / 3.0) * (extents.y * extents.y + extents.y * extents.y)); (p_mass / 3.0) * (extents.x * extents.x + extents.y * extents.y));
} }
void CapsuleShape3DSW::_setup(real_t p_height, real_t p_radius) { void CapsuleShape3DSW::_setup(real_t p_height, real_t p_radius) {
@ -807,7 +807,7 @@ Vector3 CylinderShape3DSW::get_moment_of_inertia(real_t p_mass) const {
return Vector3( return Vector3(
(p_mass / 3.0) * (extents.y * extents.y + extents.z * extents.z), (p_mass / 3.0) * (extents.y * extents.y + extents.z * extents.z),
(p_mass / 3.0) * (extents.x * extents.x + extents.z * extents.z), (p_mass / 3.0) * (extents.x * extents.x + extents.z * extents.z),
(p_mass / 3.0) * (extents.y * extents.y + extents.y * extents.y)); (p_mass / 3.0) * (extents.x * extents.x + extents.y * extents.y));
} }
void CylinderShape3DSW::_setup(real_t p_height, real_t p_radius) { void CylinderShape3DSW::_setup(real_t p_height, real_t p_radius) {
@ -1064,7 +1064,7 @@ Vector3 ConvexPolygonShape3DSW::get_moment_of_inertia(real_t p_mass) const {
return Vector3( return Vector3(
(p_mass / 3.0) * (extents.y * extents.y + extents.z * extents.z), (p_mass / 3.0) * (extents.y * extents.y + extents.z * extents.z),
(p_mass / 3.0) * (extents.x * extents.x + extents.z * extents.z), (p_mass / 3.0) * (extents.x * extents.x + extents.z * extents.z),
(p_mass / 3.0) * (extents.y * extents.y + extents.y * extents.y)); (p_mass / 3.0) * (extents.x * extents.x + extents.y * extents.y));
} }
void ConvexPolygonShape3DSW::_setup(const Vector<Vector3> &p_vertices) { void ConvexPolygonShape3DSW::_setup(const Vector<Vector3> &p_vertices) {
@ -1424,7 +1424,7 @@ Vector3 ConcavePolygonShape3DSW::get_moment_of_inertia(real_t p_mass) const {
return Vector3( return Vector3(
(p_mass / 3.0) * (extents.y * extents.y + extents.z * extents.z), (p_mass / 3.0) * (extents.y * extents.y + extents.z * extents.z),
(p_mass / 3.0) * (extents.x * extents.x + extents.z * extents.z), (p_mass / 3.0) * (extents.x * extents.x + extents.z * extents.z),
(p_mass / 3.0) * (extents.y * extents.y + extents.y * extents.y)); (p_mass / 3.0) * (extents.x * extents.x + extents.y * extents.y));
} }
struct _VolumeSW_BVH_Element { struct _VolumeSW_BVH_Element {
@ -1662,7 +1662,7 @@ Vector3 HeightMapShape3DSW::get_moment_of_inertia(real_t p_mass) const {
return Vector3( return Vector3(
(p_mass / 3.0) * (extents.y * extents.y + extents.z * extents.z), (p_mass / 3.0) * (extents.y * extents.y + extents.z * extents.z),
(p_mass / 3.0) * (extents.x * extents.x + extents.z * extents.z), (p_mass / 3.0) * (extents.x * extents.x + extents.z * extents.z),
(p_mass / 3.0) * (extents.y * extents.y + extents.y * extents.y)); (p_mass / 3.0) * (extents.x * extents.x + extents.y * extents.y));
} }
void HeightMapShape3DSW::_setup(Vector<real_t> p_heights, int p_width, int p_depth, real_t p_cell_size) { void HeightMapShape3DSW::_setup(Vector<real_t> p_heights, int p_width, int p_depth, real_t p_cell_size) {