326 lines
9.8 KiB
C++
326 lines
9.8 KiB
C++
// This code is in the public domain -- castano@gmail.com
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#include "nvmesh.h" // pch
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#include "Util.h"
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#include "nvmesh/halfedge/Mesh.h"
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#include "nvmesh/halfedge/Face.h"
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#include "nvmesh/halfedge/Vertex.h"
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#include "nvmath/Vector.inl"
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#include "nvcore/Array.inl"
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using namespace nv;
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// Determine if the given mesh is a quad mesh.
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bool nv::isQuadMesh(const HalfEdge::Mesh * mesh)
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{
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nvDebugCheck(mesh != NULL);
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const uint faceCount = mesh->faceCount();
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for(uint i = 0; i < faceCount; i++) {
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const HalfEdge::Face * face = mesh->faceAt(i);
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if (face->edgeCount() != 4) {
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return false;
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}
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}
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return true;
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}
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bool nv::isTriangularMesh(const HalfEdge::Mesh * mesh)
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{
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for (HalfEdge::Mesh::ConstFaceIterator it(mesh->faces()); !it.isDone(); it.advance())
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{
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const HalfEdge::Face * face = it.current();
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if (face->edgeCount() != 3) return false;
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}
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return true;
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}
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uint nv::countMeshTriangles(const HalfEdge::Mesh * mesh)
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{
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const uint faceCount = mesh->faceCount();
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uint triangleCount = 0;
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for (uint f = 0; f < faceCount; f++)
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{
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const HalfEdge::Face * face = mesh->faceAt(f);
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uint edgeCount = face->edgeCount();
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nvDebugCheck(edgeCount > 2);
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triangleCount += edgeCount - 2;
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}
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return triangleCount;
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}
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const HalfEdge::Vertex * nv::findBoundaryVertex(const HalfEdge::Mesh * mesh)
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{
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const uint vertexCount = mesh->vertexCount();
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for (uint v = 0; v < vertexCount; v++)
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{
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const HalfEdge::Vertex * vertex = mesh->vertexAt(v);
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if (vertex->isBoundary()) return vertex;
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}
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return NULL;
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}
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HalfEdge::Mesh * nv::unifyVertices(const HalfEdge::Mesh * inputMesh)
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{
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HalfEdge::Mesh * mesh = new HalfEdge::Mesh;
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// Only add the first colocal.
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const uint vertexCount = inputMesh->vertexCount();
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for (uint v = 0; v < vertexCount; v++) {
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const HalfEdge::Vertex * vertex = inputMesh->vertexAt(v);
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if (vertex->isFirstColocal()) {
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mesh->addVertex(vertex->pos);
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}
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}
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nv::Array<uint> indexArray;
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// Add new faces pointing to first colocals.
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uint faceCount = inputMesh->faceCount();
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for (uint f = 0; f < faceCount; f++) {
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const HalfEdge::Face * face = inputMesh->faceAt(f);
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indexArray.clear();
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for (HalfEdge::Face::ConstEdgeIterator it(face->edges()); !it.isDone(); it.advance()) {
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const HalfEdge::Edge * edge = it.current();
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const HalfEdge::Vertex * vertex = edge->vertex->firstColocal();
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indexArray.append(vertex->id);
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}
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mesh->addFace(indexArray);
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}
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mesh->linkBoundary();
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return mesh;
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}
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#include "nvmath/Basis.h"
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static bool pointInTriangle(const Vector2 & p, const Vector2 & a, const Vector2 & b, const Vector2 & c)
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{
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return triangleArea(a, b, p) >= 0.00001f &&
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triangleArea(b, c, p) >= 0.00001f &&
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triangleArea(c, a, p) >= 0.00001f;
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}
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// This is doing a simple ear-clipping algorithm that skips invalid triangles. Ideally, we should
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// also sort the ears by angle, start with the ones that have the smallest angle and proceed in order.
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HalfEdge::Mesh * nv::triangulate(const HalfEdge::Mesh * inputMesh)
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{
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HalfEdge::Mesh * mesh = new HalfEdge::Mesh;
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// Add all vertices.
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const uint vertexCount = inputMesh->vertexCount();
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for (uint v = 0; v < vertexCount; v++) {
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const HalfEdge::Vertex * vertex = inputMesh->vertexAt(v);
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mesh->addVertex(vertex->pos);
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}
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Array<int> polygonVertices;
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Array<float> polygonAngles;
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Array<Vector2> polygonPoints;
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const uint faceCount = inputMesh->faceCount();
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for (uint f = 0; f < faceCount; f++)
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{
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const HalfEdge::Face * face = inputMesh->faceAt(f);
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nvDebugCheck(face != NULL);
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const uint edgeCount = face->edgeCount();
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nvDebugCheck(edgeCount >= 3);
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polygonVertices.clear();
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polygonVertices.reserve(edgeCount);
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if (edgeCount == 3) {
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// Simple case for triangles.
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for (HalfEdge::Face::ConstEdgeIterator it(face->edges()); !it.isDone(); it.advance())
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{
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const HalfEdge::Edge * edge = it.current();
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const HalfEdge::Vertex * vertex = edge->vertex;
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polygonVertices.append(vertex->id);
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}
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int v0 = polygonVertices[0];
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int v1 = polygonVertices[1];
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int v2 = polygonVertices[2];
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mesh->addFace(v0, v1, v2);
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}
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else {
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// Build 2D polygon projecting vertices onto normal plane.
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// Faces are not necesarily planar, this is for example the case, when the face comes from filling a hole. In such cases
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// it's much better to use the best fit plane.
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const Vector3 fn = face->normal();
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Basis basis;
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basis.buildFrameForDirection(fn);
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polygonPoints.clear();
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polygonPoints.reserve(edgeCount);
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polygonAngles.clear();
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polygonAngles.reserve(edgeCount);
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for (HalfEdge::Face::ConstEdgeIterator it(face->edges()); !it.isDone(); it.advance())
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{
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const HalfEdge::Edge * edge = it.current();
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const HalfEdge::Vertex * vertex = edge->vertex;
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polygonVertices.append(vertex->id);
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Vector2 p;
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p.x = dot(basis.tangent, vertex->pos);
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p.y = dot(basis.bitangent, vertex->pos);
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polygonPoints.append(p);
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}
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polygonAngles.resize(edgeCount);
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while (polygonVertices.size() > 2) {
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uint size = polygonVertices.size();
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// Update polygon angles. @@ Update only those that have changed.
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float minAngle = 2 * PI;
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uint bestEar = 0; // Use first one if none of them is valid.
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bool bestIsValid = false;
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for (uint i = 0; i < size; i++) {
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uint i0 = i;
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uint i1 = (i+1) % size; // Use Sean's polygon interation trick.
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uint i2 = (i+2) % size;
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Vector2 p0 = polygonPoints[i0];
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Vector2 p1 = polygonPoints[i1];
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Vector2 p2 = polygonPoints[i2];
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float d = clamp(dot(p0-p1, p2-p1) / (length(p0-p1) * length(p2-p1)), -1.0f, 1.0f);
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float angle = acosf(d);
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float area = triangleArea(p0, p1, p2);
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if (area < 0.0f) angle = 2.0f * PI - angle;
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polygonAngles[i1] = angle;
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if (angle < minAngle || !bestIsValid) {
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// Make sure this is a valid ear, if not, skip this point.
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bool valid = true;
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for (uint j = 0; j < size; j++) {
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if (j == i0 || j == i1 || j == i2) continue;
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Vector2 p = polygonPoints[j];
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if (pointInTriangle(p, p0, p1, p2)) {
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valid = false;
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break;
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}
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}
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if (valid || !bestIsValid) {
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minAngle = angle;
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bestEar = i1;
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bestIsValid = valid;
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}
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}
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}
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nvDebugCheck(minAngle <= 2 * PI);
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// Clip best ear:
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uint i0 = (bestEar+size-1) % size;
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uint i1 = (bestEar+0) % size;
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uint i2 = (bestEar+1) % size;
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int v0 = polygonVertices[i0];
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int v1 = polygonVertices[i1];
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int v2 = polygonVertices[i2];
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mesh->addFace(v0, v1, v2);
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polygonVertices.removeAt(i1);
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polygonPoints.removeAt(i1);
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polygonAngles.removeAt(i1);
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}
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}
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#if 0
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uint i = 0;
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while (polygonVertices.size() > 2 && i < polygonVertices.size()) {
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uint size = polygonVertices.size();
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uint i0 = (i+0) % size;
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uint i1 = (i+1) % size;
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uint i2 = (i+2) % size;
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const HalfEdge::Vertex * v0 = polygonVertices[i0];
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const HalfEdge::Vertex * v1 = polygonVertices[i1];
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const HalfEdge::Vertex * v2 = polygonVertices[i2];
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const Vector3 p0 = v0->pos;
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const Vector3 p1 = v1->pos;
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const Vector3 p2 = v2->pos;
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const Vector3 e0 = p2 - p1;
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const Vector3 e1 = p0 - p1;
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// If this ear forms a valid triangle, setup relations, remove v1 and repeat.
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Vector3 n = cross(e0, e1);
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float len = dot(fn, n); // = sin(angle)
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float angle = asin(len);
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if (len > 0.0f) {
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mesh->addFace(v0->id(), v1->id(), v2->id());
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polygonVertices.removeAt(i1);
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polygonAngles.removeAt(i1);
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if (i2 > i1) i2--;
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// @@ Update angles at i0 and i2
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}
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else {
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i++;
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}
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}
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// @@ Create a few degenerate triangles to avoid introducing holes.
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i = 0;
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const uint size = polygonVertices.size();
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while (i < size - 2) {
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uint i0 = (i+0) % size;
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uint i1 = (i+1) % size;
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uint i2 = (i+2) % size;
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const HalfEdge::Vertex * v0 = polygonVertices[i0];
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const HalfEdge::Vertex * v1 = polygonVertices[i1];
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const HalfEdge::Vertex * v2 = polygonVertices[i2];
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mesh->addFace(v0->id(), v1->id(), v2->id());
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i++;
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}
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#endif
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}
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mesh->linkBoundary();
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return mesh;
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}
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