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[physics] adding a physics body to an entity will now walk down the e…
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…ntity's children and create a compound shape, an example is the flight helmet in the objects world, which is made of multiple meshes/entities yet is now behaving a single physics body
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@PanosK92
PanosK92 committed Jan 14, 2025
1 parent 40c2328 commit 8c25f2d
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Showing 3 changed files with 91 additions and 75 deletions.
4 changes: 4 additions & 0 deletions runtime/Game/Game.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -427,6 +427,10 @@ namespace spartan
entity->SetObjectName("flight_helmet");
entity->SetPosition(Vector3(0.0f, 0.1f, 0.0f));
entity->SetScale(Vector3(1.7f, 1.7f, 1.7f));

PhysicsBody* physics_body = entity->AddComponent<PhysicsBody>().get();
physics_body->SetMass(8.0f);
physics_body->SetShapeType(PhysicsShape::Mesh);
}

// damaged helmet
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160 changes: 87 additions & 73 deletions runtime/World/Components/PhysicsBody.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -859,9 +859,9 @@ namespace spartan
1.0f, // height scale
terrain->GetMinY(), // min height
terrain->GetMaxY(), // max height
1, // Up axis (0=x, 1=y, 2=z)
PHY_FLOAT, // Data type
false // Flip quad edges or not
1, // up axis (0=x, 1=y, 2=z)
PHY_FLOAT, // data type
false // flip quad edges or not
);

shape_local->setLocalScaling(vector_to_bt(size));
Expand All @@ -879,83 +879,97 @@ namespace spartan

case PhysicsShape::Mesh:
{
// get renderable
shared_ptr<Renderable> renderable = GetEntity()->GetComponent<Renderable>();
if (!renderable)
function<void(Entity*, btCompoundShape*)> recursive_renderable_to_shape = [&](Entity* entity, btCompoundShape* compoundShape)
{
SP_LOG_WARNING("PhysicsShape::Mesh requires a renderable component to be present");
return;
}

// get geometry
renderable->GetGeometry(&m_indices, &m_vertices);
if (m_vertices.empty())
{
SP_LOG_WARNING("PhysicsShape::Mesh requires the renderable component to contain vertices");
return;
}

// determine how much detail is needed for this shape
const bool is_enterable = can_player_fit(GetEntity(), m_vertices, size);
const bool convex_hull = !is_enterable;

if (convex_hull)
{
// create
btConvexHullShape* shape_convex = new btConvexHullShape(
reinterpret_cast<btScalar*>(&m_vertices[0]),
static_cast<uint32_t>(m_vertices.size()),
static_cast<uint32_t>(sizeof(RHI_Vertex_PosTexNorTan))
);
shape_convex->optimizeConvexHull();

// add to compound
btCompoundShape* shape_compound = new btCompoundShape();
if (renderable->HasInstancing())
// get renderable
shared_ptr<Renderable> renderable = entity->GetComponent<Renderable>();
if (renderable)
{
for (uint32_t instance_index = 0; instance_index < renderable->GetInstanceCount(); instance_index++)
// get geometry
vector<uint32_t> indices;
vector<RHI_Vertex_PosTexNorTan> vertices;
renderable->GetGeometry(&indices, &vertices);

if (vertices.empty())
{
Matrix world_transform = renderable->GetInstanceTransform(instance_index);
shape_compound->addChildShape(compute_transform(world_transform.GetTranslation(), world_transform.GetRotation(), world_transform.GetScale()), shape_convex);
SP_LOG_WARNING("PhysicsShape::Mesh requires the renderable component to contain vertices");
return;
}

// determine how much detail is needed for this shape
const bool is_enterable = can_player_fit(entity, vertices, size);
const bool convex_hull = !is_enterable;

if (convex_hull)
{
// create convex hull shape
btConvexHullShape* shape_convex = new btConvexHullShape(
reinterpret_cast<btScalar*>(&vertices[0]),
static_cast<uint32_t>(vertices.size()),
static_cast<uint32_t>(sizeof(RHI_Vertex_PosTexNorTan))
);
shape_convex->optimizeConvexHull();

// add to compound
if (renderable->HasInstancing())
{
for (uint32_t instance_index = 0; instance_index < renderable->GetInstanceCount(); instance_index++)
{
Matrix world_transform = renderable->GetInstanceTransform(instance_index);
compoundShape->addChildShape(compute_transform(world_transform.GetTranslation(), world_transform.GetRotation(), world_transform.GetScale()), shape_convex);
}
}
else
{
compoundShape->addChildShape(compute_transform(Vector3::Zero, Quaternion::Identity, size), shape_convex);
}
}
else
{
// simplify the geometry if not convex hull
geometry_processing::simplify(indices, vertices, static_cast<size_t>((indices.size() / 3) * 0.05f));

// create triangle mesh shape
btTriangleIndexVertexArray* index_vertex_array = new btTriangleIndexVertexArray(
static_cast<int>(indices.size() / 3),
reinterpret_cast<int*>(&indices[0]),
sizeof(uint32_t) * 3,
static_cast<int>(vertices.size()),
reinterpret_cast<float*>(&vertices[0].pos[0]),
sizeof(vertices[0])
);

btBvhTriangleMeshShape* shape_triangle_mesh = new btBvhTriangleMeshShape(
index_vertex_array,
true // bvh for optimized collisions
);

shape_triangle_mesh->setLocalScaling(vector_to_bt(size));

// set properties for kinematic static collision
m_is_kinematic = true;
m_mass = 0.0f;

compoundShape->addChildShape(compute_transform(Vector3::Zero, Quaternion::Identity, size), shape_triangle_mesh);
}
}
else

// recursively process all children
vector<Entity*> children = entity->GetChildren();
for (Entity* child : children)
{
shape_compound->addChildShape(compute_transform(Vector3::Zero, Quaternion::Identity, size), shape_convex);
recursive_renderable_to_shape(child, compoundShape);
}

m_shape = shape_compound;
}
else
{
geometry_processing::simplify(m_indices, m_vertices, static_cast<size_t>((m_indices.size() / 3) * 0.05f));

// create a btTriangleIndexVertexArray using indices and vertices
btTriangleIndexVertexArray* index_vertex_array = new btTriangleIndexVertexArray(
static_cast<int>(m_indices.size() / 3), // number of triangles
reinterpret_cast<int*>(&m_indices[0]), // pointer to indices
sizeof(uint32_t) * 3, // stride between index sets (3 indices per triangle)
static_cast<int>(m_vertices.size()), // number of vertices
reinterpret_cast<float*>(&m_vertices[0].pos[0]), // pointer to vertex positions
sizeof(m_vertices[0]) // stride between vertices
);

// create a btBvhTriangleMeshShape using the index-vertex array
btBvhTriangleMeshShape* shape_triangle_mesh = new btBvhTriangleMeshShape(
index_vertex_array,
true // bvh for optimized collisions
);

// we only need to set the scale as the rotation and position is set set in btMotionState
shape_triangle_mesh->setLocalScaling(vector_to_bt(size));

// btBvhTriangleMeshShape is static and expensive to collide with
m_is_kinematic = true;
m_mass = 0.0f;

m_shape = shape_triangle_mesh;
}

};

// create the compound shape
btCompoundShape* shape_compound = new btCompoundShape();

// start the recursive process for this entity
recursive_renderable_to_shape(GetEntity(), shape_compound);

m_shape = shape_compound;

break;
}
}
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2 changes: 0 additions & 2 deletions runtime/World/Components/PhysicsBody.h
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Original file line number Diff line number Diff line change
Expand Up @@ -185,7 +185,5 @@ namespace spartan
void* m_rigid_body = nullptr;
std::shared_ptr<Car> m_car = nullptr;
std::vector<Constraint*> m_constraints;
std::vector<RHI_Vertex_PosTexNorTan> m_vertices;
std::vector<uint32_t> m_indices;
};
}

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