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fix mesh size, decouple mesh topology from geometry, add polygon triangulation to make mass calculation O(n) in memory

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This commit is contained in:
Irlan
2017-02-02 14:02:54 -02:00
parent 4f18e46268
commit d59b67c3c3
5 changed files with 158 additions and 156 deletions
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112
src/bounce/dynamics/shapes/hull_shape.cpp
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@@ -39,41 +39,6 @@ void b3HullShape::Swap(const b3HullShape& other)
void b3HullShape::ComputeMass(b3MassData* massData, float32 density) const
{
// Build triangles for hull
b3StackArray<b3Triangle, 256> triangles;
// Use a small buffer for polygons.
u32 polygon[B3_MAX_HULL_FEATURES];
u32 vCount = 0;
// Convert polygons to triangles
for (u32 i = 0; i < m_hull->faceCount; ++i)
{
// Build convex polygon for loop
const b3Face* face = m_hull->GetFace(i);
const b3HalfEdge* begin = m_hull->GetEdge(face->edge);
const b3HalfEdge* edge = begin;
do
{
polygon[vCount++] = u32(edge->origin);
edge = m_hull->GetEdge(edge->next);
} while (edge != begin);
// Triangulate convex polygon
B3_ASSERT(vCount > 2);
for (u32 j = 1; j < vCount - 1; ++j)
{
b3Triangle triangle;
triangle.v1 = polygon[0];
triangle.v2 = polygon[j];
triangle.v3 = polygon[j + 1];
triangles.PushBack(triangle);
}
vCount = 0;
}
vCount = 0;
// Compute mass data
b3Vec3 center(0.0f, 0.0f, 0.0f);
float32 volume = 0.0f;
@@ -92,41 +57,56 @@ void b3HullShape::ComputeMass(b3MassData* massData, float32 density) const
b3Vec3 diag(0.0f, 0.0f, 0.0f);
b3Vec3 offDiag(0.0f, 0.0f, 0.0f);
for (u32 i = 0; i < triangles.Count(); ++i)
// Triangulate convex polygons
for (u32 i = 0; i < m_hull->faceCount; ++i)
{
const b3Triangle* triangle = triangles.Get(i);
b3Vec3 v2 = m_hull->GetVertex(triangle->v1);
b3Vec3 v3 = m_hull->GetVertex(triangle->v2);
b3Vec3 v4 = m_hull->GetVertex(triangle->v3);
b3Vec3 tetraCenter = inv4 * (v1 + v2 + v3 + v4);
b3Vec3 e1 = v2 - v1;
b3Vec3 e2 = v3 - v1;
b3Vec3 e3 = v4 - v1;
float32 det = b3Det(e1, e2, e3);
float32 tetraVolume = inv6 * det;
// Volume weighted center of mass
center += tetraVolume * tetraCenter;
volume += tetraVolume;
// Volume weighted inertia tensor
// https://github.com/melax/sandbox
for (u32 j = 0; j < 3; ++j)
const b3Face* face = m_hull->GetFace(i);
const b3HalfEdge* begin = m_hull->GetEdge(face->edge);
const b3HalfEdge* edge = m_hull->GetEdge(begin->next);
do
{
u32 j1 = (j + 1) % 3;
u32 j2 = (j + 2) % 3;
u32 i1 = begin->origin;
u32 i2 = edge->origin;
const b3HalfEdge* next = m_hull->GetEdge(edge->next);
u32 i3 = next->origin;
diag[j] += inv60 * det *
(e1[j] * e2[j] + e2[j] * e3[j] + e3[j] * e1[j] +
e1[j] * e1[j] + e2[j] * e2[j] + e3[j] * e3[j]);
b3Vec3 v2 = m_hull->vertices[i1];
b3Vec3 v3 = m_hull->vertices[i2];
b3Vec3 v4 = m_hull->vertices[i3];
//
b3Vec3 tetraCenter = inv4 * (v1 + v2 + v3 + v4);
offDiag[j] += inv120 * det *
(e1[j1] * e2[j2] + e2[j1] * e3[j2] + e3[j1] * e1[j2] +
e1[j1] * e3[j2] + e2[j1] * e1[j2] + e3[j1] * e2[j2] +
e1[j1] * e1[j2] * 2.0f + e2[j1] * e2[j2] * 2.0f + e3[j1] * e3[j2] * 2.0f);
}
b3Vec3 e1 = v2 - v1;
b3Vec3 e2 = v3 - v1;
b3Vec3 e3 = v4 - v1;
float32 det = b3Det(e1, e2, e3);
float32 tetraVolume = inv6 * det;
// Volume weighted center of mass
center += tetraVolume * tetraCenter;
volume += tetraVolume;
// Volume weighted inertia tensor
// https://github.com/melax/sandbox
for (u32 j = 0; j < 3; ++j)
{
u32 j1 = (j + 1) % 3;
u32 j2 = (j + 2) % 3;
diag[j] += inv60 * det *
(e1[j] * e2[j] + e2[j] * e3[j] + e3[j] * e1[j] +
e1[j] * e1[j] + e2[j] * e2[j] + e3[j] * e3[j]);
offDiag[j] += inv120 * det *
(e1[j1] * e2[j2] + e2[j1] * e3[j2] + e3[j1] * e1[j2] +
e1[j1] * e3[j2] + e2[j1] * e1[j2] + e3[j1] * e2[j2] +
e1[j1] * e1[j2] * 2.0f + e2[j1] * e2[j2] * 2.0f + e3[j1] * e3[j2] * 2.0f);
}
edge = next;
} while (m_hull->GetEdge(edge->next) != begin);
}
B3_ASSERT(volume > 0.0f);