godot/thirdparty/thekla_atlas/nvmesh/param/AtlasBuilder.cpp

1321 lines
38 KiB
C++

// This code is in the public domain -- castano@gmail.com
#include "nvmesh.h" // pch
#include "AtlasBuilder.h"
#include "Util.h"
#include "nvmesh/halfedge/Mesh.h"
#include "nvmesh/halfedge/Face.h"
#include "nvmesh/halfedge/Vertex.h"
#include "nvmath/Matrix.inl"
#include "nvmath/Vector.inl"
//#include "nvcore/IntroSort.h"
#include "nvcore/Array.inl"
#include <algorithm> // std::sort
#include <float.h> // FLT_MAX
#include <limits.h> // UINT_MAX
using namespace nv;
namespace
{
// Dummy implementation of a priority queue using sort at insertion.
// - Insertion is o(n)
// - Smallest element goes at the end, so that popping it is o(1).
// - Resorting is n*log(n)
// @@ Number of elements in the queue is usually small, and we'd have to rebalance often. I'm not sure it's worth implementing a heap.
// @@ Searcing at removal would remove the need for sorting when priorities change.
struct PriorityQueue
{
PriorityQueue(uint size = UINT_MAX) : maxSize(size) {}
void push(float priority, uint face) {
uint i = 0;
const uint count = pairs.count();
for (; i < count; i++) {
if (pairs[i].priority > priority) break;
}
Pair p = { priority, face };
pairs.insertAt(i, p);
if (pairs.count() > maxSize) {
pairs.removeAt(0);
}
}
// push face out of order, to be sorted later.
void push(uint face) {
Pair p = { 0.0f, face };
pairs.append(p);
}
uint pop() {
uint f = pairs.back().face;
pairs.pop_back();
return f;
}
void sort() {
//nv::sort(pairs); // @@ My intro sort appears to be much slower than it should!
std::sort(pairs.buffer(), pairs.buffer() + pairs.count());
}
void clear() {
pairs.clear();
}
uint count() const { return pairs.count(); }
float firstPriority() const { return pairs.back().priority; }
const uint maxSize;
struct Pair {
bool operator <(const Pair & p) const { return priority > p.priority; } // !! Sort in inverse priority order!
float priority;
uint face;
};
Array<Pair> pairs;
};
static bool isNormalSeam(const HalfEdge::Edge * edge) {
return (edge->vertex->nor != edge->pair->next->vertex->nor || edge->next->vertex->nor != edge->pair->vertex->nor);
}
static bool isTextureSeam(const HalfEdge::Edge * edge) {
return (edge->vertex->tex != edge->pair->next->vertex->tex || edge->next->vertex->tex != edge->pair->vertex->tex);
}
} // namespace
struct nv::ChartBuildData
{
ChartBuildData(int id) : id(id) {
planeNormal = Vector3(0);
centroid = Vector3(0);
coneAxis = Vector3(0);
coneAngle = 0;
area = 0;
boundaryLength = 0;
normalSum = Vector3(0);
centroidSum = Vector3(0);
}
int id;
// Proxy info:
Vector3 planeNormal;
Vector3 centroid;
Vector3 coneAxis;
float coneAngle;
float area;
float boundaryLength;
Vector3 normalSum;
Vector3 centroidSum;
Array<uint> seeds; // @@ These could be a pointers to the HalfEdge faces directly.
Array<uint> faces;
PriorityQueue candidates;
};
AtlasBuilder::AtlasBuilder(const HalfEdge::Mesh * m) : mesh(m), facesLeft(m->faceCount())
{
const uint faceCount = m->faceCount();
faceChartArray.resize(faceCount, -1);
faceCandidateArray.resize(faceCount, -1);
// @@ Floyd for the whole mesh is too slow. We could compute floyd progressively per patch as the patch grows. We need a better solution to compute most central faces.
//computeShortestPaths();
// Precompute edge lengths and face areas.
uint edgeCount = m->edgeCount();
edgeLengths.resize(edgeCount);
for (uint i = 0; i < edgeCount; i++) {
uint id = m->edgeAt(i)->id;
nvDebugCheck(id / 2 == i);
edgeLengths[i] = m->edgeAt(i)->length();
}
faceAreas.resize(faceCount);
for (uint i = 0; i < faceCount; i++) {
faceAreas[i] = m->faceAt(i)->area();
}
}
AtlasBuilder::~AtlasBuilder()
{
const uint chartCount = chartArray.count();
for (uint i = 0; i < chartCount; i++)
{
delete chartArray[i];
}
}
void AtlasBuilder::markUnchartedFaces(const Array<uint> & unchartedFaces)
{
const uint unchartedFaceCount = unchartedFaces.count();
for (uint i = 0; i < unchartedFaceCount; i++){
uint f = unchartedFaces[i];
faceChartArray[f] = -2;
//faceCandidateArray[f] = -2; // @@ ?
removeCandidate(f);
}
nvDebugCheck(facesLeft >= unchartedFaceCount);
facesLeft -= unchartedFaceCount;
}
void AtlasBuilder::computeShortestPaths()
{
const uint faceCount = mesh->faceCount();
shortestPaths.resize(faceCount*faceCount, FLT_MAX);
// Fill edges:
for (uint i = 0; i < faceCount; i++)
{
shortestPaths[i*faceCount + i] = 0.0f;
const HalfEdge::Face * face_i = mesh->faceAt(i);
Vector3 centroid_i = face_i->centroid();
for (HalfEdge::Face::ConstEdgeIterator it(face_i->edges()); !it.isDone(); it.advance())
{
const HalfEdge::Edge * edge = it.current();
if (!edge->isBoundary())
{
const HalfEdge::Face * face_j = edge->pair->face;
uint j = face_j->id;
Vector3 centroid_j = face_j->centroid();
shortestPaths[i*faceCount + j] = shortestPaths[j*faceCount + i] = length(centroid_i - centroid_j);
}
}
}
// Use Floyd-Warshall algorithm to compute all paths:
for (uint k = 0; k < faceCount; k++)
{
for (uint i = 0; i < faceCount; i++)
{
for (uint j = 0; j < faceCount; j++)
{
shortestPaths[i*faceCount + j] = min(shortestPaths[i*faceCount + j], shortestPaths[i*faceCount + k]+shortestPaths[k*faceCount + j]);
}
}
}
}
void AtlasBuilder::placeSeeds(float threshold, uint maxSeedCount)
{
// Instead of using a predefiened number of seeds:
// - Add seeds one by one, growing chart until a certain treshold.
// - Undo charts and restart growing process.
// @@ How can we give preference to faces far from sharp features as in the LSCM paper?
// - those points can be found using a simple flood filling algorithm.
// - how do we weight the probabilities?
for (uint i = 0; i < maxSeedCount; i++)
{
if (facesLeft == 0) {
// No faces left, stop creating seeds.
break;
}
createRandomChart(threshold);
}
}
void AtlasBuilder::createRandomChart(float threshold)
{
ChartBuildData * chart = new ChartBuildData(chartArray.count());
chartArray.append(chart);
// Pick random face that is not used by any chart yet.
uint randomFaceIdx = rand.getRange(facesLeft - 1);
uint i = 0;
for (uint f = 0; f != randomFaceIdx; f++, i++)
{
while (faceChartArray[i] != -1) i++;
}
while (faceChartArray[i] != -1) i++;
chart->seeds.append(i);
addFaceToChart(chart, i, true);
// Grow the chart as much as possible within the given threshold.
growChart(chart, threshold * 0.5f, facesLeft);
//growCharts(threshold - threshold * 0.75f / chartCount(), facesLeft);
}
void AtlasBuilder::addFaceToChart(ChartBuildData * chart, uint f, bool recomputeProxy)
{
// Add face to chart.
chart->faces.append(f);
nvDebugCheck(faceChartArray[f] == -1);
faceChartArray[f] = chart->id;
facesLeft--;
// Update area and boundary length.
chart->area = evaluateChartArea(chart, f);
chart->boundaryLength = evaluateBoundaryLength(chart, f);
chart->normalSum = evaluateChartNormalSum(chart, f);
chart->centroidSum = evaluateChartCentroidSum(chart, f);
if (recomputeProxy) {
// Update proxy and candidate's priorities.
updateProxy(chart);
}
// Update candidates.
removeCandidate(f);
updateCandidates(chart, f);
updatePriorities(chart);
}
// @@ Get N best candidates in one pass.
const AtlasBuilder::Candidate & AtlasBuilder::getBestCandidate() const
{
uint best = 0;
float bestCandidateMetric = FLT_MAX;
const uint candidateCount = candidateArray.count();
nvCheck(candidateCount > 0);
for (uint i = 0; i < candidateCount; i++)
{
const Candidate & candidate = candidateArray[i];
if (candidate.metric < bestCandidateMetric) {
bestCandidateMetric = candidate.metric;
best = i;
}
}
return candidateArray[best];
}
// Returns true if any of the charts can grow more.
bool AtlasBuilder::growCharts(float threshold, uint faceCount)
{
#if 1 // Using one global list.
faceCount = min(faceCount, facesLeft);
for (uint i = 0; i < faceCount; i++)
{
const Candidate & candidate = getBestCandidate();
if (candidate.metric > threshold) {
return false; // Can't grow more.
}
addFaceToChart(candidate.chart, candidate.face);
}
return facesLeft != 0; // Can continue growing.
#else // Using one list per chart.
bool canGrowMore = false;
const uint chartCount = chartArray.count();
for (uint i = 0; i < chartCount; i++)
{
if (growChart(chartArray[i], threshold, faceCount))
{
canGrowMore = true;
}
}
return canGrowMore;
#endif
}
bool AtlasBuilder::growChart(ChartBuildData * chart, float threshold, uint faceCount)
{
// Try to add faceCount faces within threshold to chart.
for (uint i = 0; i < faceCount; )
{
if (chart->candidates.count() == 0 || chart->candidates.firstPriority() > threshold)
{
return false;
}
uint f = chart->candidates.pop();
if (faceChartArray[f] == -1)
{
addFaceToChart(chart, f);
i++;
}
}
if (chart->candidates.count() == 0 || chart->candidates.firstPriority() > threshold)
{
return false;
}
return true;
}
void AtlasBuilder::resetCharts()
{
const uint faceCount = mesh->faceCount();
for (uint i = 0; i < faceCount; i++)
{
faceChartArray[i] = -1;
faceCandidateArray[i] = -1;
}
facesLeft = faceCount;
candidateArray.clear();
const uint chartCount = chartArray.count();
for (uint i = 0; i < chartCount; i++)
{
ChartBuildData * chart = chartArray[i];
const uint seed = chart->seeds.back();
chart->area = 0.0f;
chart->boundaryLength = 0.0f;
chart->normalSum = Vector3(0);
chart->centroidSum = Vector3(0);
chart->faces.clear();
chart->candidates.clear();
addFaceToChart(chart, seed);
}
}
void AtlasBuilder::updateCandidates(ChartBuildData * chart, uint f)
{
const HalfEdge::Face * face = mesh->faceAt(f);
// Traverse neighboring faces, add the ones that do not belong to any chart yet.
for (HalfEdge::Face::ConstEdgeIterator it(face->edges()); !it.isDone(); it.advance())
{
const HalfEdge::Edge * edge = it.current()->pair;
if (!edge->isBoundary())
{
uint f = edge->face->id;
if (faceChartArray[f] == -1)
{
chart->candidates.push(f);
}
}
}
}
void AtlasBuilder::updateProxies()
{
const uint chartCount = chartArray.count();
for (uint i = 0; i < chartCount; i++)
{
updateProxy(chartArray[i]);
}
}
namespace {
float absoluteSum(Vector4::Arg v)
{
return fabs(v.x) + fabs(v.y) + fabs(v.z) + fabs(v.w);
}
//#pragma message(NV_FILE_LINE "FIXME: Using the c=cos(teta) substitution, the equation system becomes linear and we can avoid the newton solver.")
struct ConeFitting
{
ConeFitting(const HalfEdge::Mesh * m, float g, float tf, float tx) : mesh(m), gamma(g), tolf(tf), tolx(tx), F(0), D(0), H(0) {
}
void addTerm(Vector3 N, float A)
{
const float c = cosf(X.w);
const float s = sinf(X.w);
const float tmp = dot(X.xyz(), N) - c;
F += tmp * tmp;
D.x += 2 * X.x * tmp;
D.y += 2 * X.y * tmp;
D.z += 2 * X.z * tmp;
D.w += 2 * s * tmp;
H(0,0) = 2 * X.x * N.x + 2 * tmp;
H(0,1) = 2 * X.x * N.y;
H(0,2) = 2 * X.x * N.z;
H(0,3) = 2 * X.x * s;
H(1,0) = 2 * X.y * N.x;
H(1,1) = 2 * X.y * N.y + 2 * tmp;
H(1,2) = 2 * X.y * N.z;
H(1,3) = 2 * X.y * s;
H(2,0) = 2 * X.z * N.x;
H(2,1) = 2 * X.z * N.y;
H(2,2) = 2 * X.z * N.z + 2 * tmp;
H(2,3) = 2 * X.z * s;
H(3,0) = 2 * s * N.x;
H(3,1) = 2 * s * N.y;
H(3,2) = 2 * s * N.z;
H(3,3) = 2 * s * s + 2 * c * tmp;
}
Vector4 solve(ChartBuildData * chart, Vector4 start)
{
const uint faceCount = chart->faces.count();
X = start;
Vector4 dX;
do {
for (uint i = 0; i < faceCount; i++)
{
const HalfEdge::Face * face = mesh->faceAt(chart->faces[i]);
addTerm(face->normal(), face->area());
}
Vector4 dX;
//solveKramer(H, D, &dX);
solveLU(H, D, &dX);
// @@ Do a full newton step and reduce by half if F doesn't decrease.
X -= gamma * dX;
// Constrain normal to be normalized.
X = Vector4(normalize(X.xyz()), X.w);
} while(absoluteSum(D) > tolf || absoluteSum(dX) > tolx);
return X;
}
HalfEdge::Mesh const * const mesh;
const float gamma;
const float tolf;
const float tolx;
Vector4 X;
float F;
Vector4 D;
Matrix H;
};
// Unnormalized face normal assuming it's a triangle.
static Vector3 triangleNormal(const HalfEdge::Face * face)
{
Vector3 p0 = face->edge->vertex->pos;
Vector3 p1 = face->edge->next->vertex->pos;
Vector3 p2 = face->edge->next->next->vertex->pos;
Vector3 e0 = p2 - p0;
Vector3 e1 = p1 - p0;
return normalizeSafe(cross(e0, e1), Vector3(0), 0.0f);
}
static Vector3 triangleNormalAreaScaled(const HalfEdge::Face * face)
{
Vector3 p0 = face->edge->vertex->pos;
Vector3 p1 = face->edge->next->vertex->pos;
Vector3 p2 = face->edge->next->next->vertex->pos;
Vector3 e0 = p2 - p0;
Vector3 e1 = p1 - p0;
return cross(e0, e1);
}
// Average of the edge midpoints weighted by the edge length.
// I want a point inside the triangle, but closer to the cirumcenter.
static Vector3 triangleCenter(const HalfEdge::Face * face)
{
Vector3 p0 = face->edge->vertex->pos;
Vector3 p1 = face->edge->next->vertex->pos;
Vector3 p2 = face->edge->next->next->vertex->pos;
float l0 = length(p1 - p0);
float l1 = length(p2 - p1);
float l2 = length(p0 - p2);
Vector3 m0 = (p0 + p1) * l0 / (l0 + l1 + l2);
Vector3 m1 = (p1 + p2) * l1 / (l0 + l1 + l2);
Vector3 m2 = (p2 + p0) * l2 / (l0 + l1 + l2);
return m0 + m1 + m2;
}
} // namespace
void AtlasBuilder::updateProxy(ChartBuildData * chart)
{
//#pragma message(NV_FILE_LINE "TODO: Use best fit plane instead of average normal.")
chart->planeNormal = normalizeSafe(chart->normalSum, Vector3(0), 0.0f);
chart->centroid = chart->centroidSum / float(chart->faces.count());
//#pragma message(NV_FILE_LINE "TODO: Experiment with conic fitting.")
// F = (Nc*Nt - cos Oc)^2 = (x*Nt_x + y*Nt_y + z*Nt_z - cos w)^2
// dF/dx = 2 * x * (x*Nt_x + y*Nt_y + z*Nt_z - cos w)
// dF/dy = 2 * y * (x*Nt_x + y*Nt_y + z*Nt_z - cos w)
// dF/dz = 2 * z * (x*Nt_x + y*Nt_y + z*Nt_z - cos w)
// dF/dw = 2 * sin w * (x*Nt_x + y*Nt_y + z*Nt_z - cos w)
// JacobianMatrix({
// 2 * x * (x*Nt_x + y*Nt_y + z*Nt_z - Cos(w)),
// 2 * y * (x*Nt_x + y*Nt_y + z*Nt_z - Cos(w)),
// 2 * z * (x*Nt_x + y*Nt_y + z*Nt_z - Cos(w)),
// 2 * Sin(w) * (x*Nt_x + y*Nt_y + z*Nt_z - Cos(w))}, {x,y,z,w})
// H[0,0] = 2 * x * Nt_x + 2 * (x*Nt_x + y*Nt_y + z*Nt_z - cos(w));
// H[0,1] = 2 * x * Nt_y;
// H[0,2] = 2 * x * Nt_z;
// H[0,3] = 2 * x * sin(w);
// H[1,0] = 2 * y * Nt_x;
// H[1,1] = 2 * y * Nt_y + 2 * (x*Nt_x + y*Nt_y + z*Nt_z - cos(w));
// H[1,2] = 2 * y * Nt_z;
// H[1,3] = 2 * y * sin(w);
// H[2,0] = 2 * z * Nt_x;
// H[2,1] = 2 * z * Nt_y;
// H[2,2] = 2 * z * Nt_z + 2 * (x*Nt_x + y*Nt_y + z*Nt_z - cos(w));
// H[2,3] = 2 * z * sin(w);
// H[3,0] = 2 * sin(w) * Nt_x;
// H[3,1] = 2 * sin(w) * Nt_y;
// H[3,2] = 2 * sin(w) * Nt_z;
// H[3,3] = 2 * sin(w) * sin(w) + 2 * cos(w) * (x*Nt_x + y*Nt_y + z*Nt_z - cos(w));
// @@ Cone fitting might be quite slow.
/*ConeFitting coneFitting(mesh, 0.1f, 0.001f, 0.001f);
Vector4 start = Vector4(chart->coneAxis, chart->coneAngle);
Vector4 solution = coneFitting.solve(chart, start);
chart->coneAxis = solution.xyz();
chart->coneAngle = solution.w;*/
}
bool AtlasBuilder::relocateSeeds()
{
bool anySeedChanged = false;
const uint chartCount = chartArray.count();
for (uint i = 0; i < chartCount; i++)
{
if (relocateSeed(chartArray[i]))
{
anySeedChanged = true;
}
}
return anySeedChanged;
}
bool AtlasBuilder::relocateSeed(ChartBuildData * chart)
{
Vector3 centroid = computeChartCentroid(chart);
const uint N = 10; // @@ Hardcoded to 10?
PriorityQueue bestTriangles(N);
// Find the first N triangles that fit the proxy best.
const uint faceCount = chart->faces.count();
for (uint i = 0; i < faceCount; i++)
{
float priority = evaluateProxyFitMetric(chart, chart->faces[i]);
bestTriangles.push(priority, chart->faces[i]);
}
// Of those, choose the most central triangle.
uint mostCentral;
float maxDistance = -1;
const uint bestCount = bestTriangles.count();
for (uint i = 0; i < bestCount; i++)
{
const HalfEdge::Face * face = mesh->faceAt(bestTriangles.pairs[i].face);
Vector3 faceCentroid = triangleCenter(face);
float distance = length(centroid - faceCentroid);
/*#pragma message(NV_FILE_LINE "TODO: Implement evaluateDistanceToBoundary.")
float distance = evaluateDistanceToBoundary(chart, bestTriangles.pairs[i].face);*/
if (distance > maxDistance)
{
maxDistance = distance;
mostCentral = bestTriangles.pairs[i].face;
}
}
nvDebugCheck(maxDistance >= 0);
// In order to prevent k-means cyles we record all the previously chosen seeds.
uint index;
if (chart->seeds.find(mostCentral, &index))
{
// Move new seed to the end of the seed array.
uint last = chart->seeds.count() - 1;
swap(chart->seeds[index], chart->seeds[last]);
return false;
}
else
{
// Append new seed.
chart->seeds.append(mostCentral);
return true;
}
}
void AtlasBuilder::removeCandidate(uint f)
{
int c = faceCandidateArray[f];
if (c != -1) {
faceCandidateArray[f] = -1;
if (c == candidateArray.count() - 1) {
candidateArray.popBack();
}
else {
candidateArray.replaceWithLast(c);
faceCandidateArray[candidateArray[c].face] = c;
}
}
}
void AtlasBuilder::updateCandidate(ChartBuildData * chart, uint f, float metric)
{
if (faceCandidateArray[f] == -1) {
const uint index = candidateArray.count();
faceCandidateArray[f] = index;
candidateArray.resize(index + 1);
candidateArray[index].face = f;
candidateArray[index].chart = chart;
candidateArray[index].metric = metric;
}
else {
int c = faceCandidateArray[f];
nvDebugCheck(c != -1);
Candidate & candidate = candidateArray[c];
nvDebugCheck(candidate.face == f);
if (metric < candidate.metric || chart == candidate.chart) {
candidate.metric = metric;
candidate.chart = chart;
}
}
}
void AtlasBuilder::updatePriorities(ChartBuildData * chart)
{
// Re-evaluate candidate priorities.
uint candidateCount = chart->candidates.count();
for (uint i = 0; i < candidateCount; i++)
{
chart->candidates.pairs[i].priority = evaluatePriority(chart, chart->candidates.pairs[i].face);
if (faceChartArray[chart->candidates.pairs[i].face] == -1)
{
updateCandidate(chart, chart->candidates.pairs[i].face, chart->candidates.pairs[i].priority);
}
}
// Sort candidates.
chart->candidates.sort();
}
// Evaluate combined metric.
float AtlasBuilder::evaluatePriority(ChartBuildData * chart, uint face)
{
// Estimate boundary length and area:
float newBoundaryLength = evaluateBoundaryLength(chart, face);
float newChartArea = evaluateChartArea(chart, face);
float F = evaluateProxyFitMetric(chart, face);
float C = evaluateRoundnessMetric(chart, face, newBoundaryLength, newChartArea);
float P = evaluateStraightnessMetric(chart, face);
// Penalize faces that cross seams, reward faces that close seams or reach boundaries.
float N = evaluateNormalSeamMetric(chart, face);
float T = evaluateTextureSeamMetric(chart, face);
//float R = evaluateCompletenessMetric(chart, face);
//float D = evaluateDihedralAngleMetric(chart, face);
// @@ Add a metric based on local dihedral angle.
// @@ Tweaking the normal and texture seam metrics.
// - Cause more impedance. Never cross 90 degree edges.
// -
float cost = float(
settings.proxyFitMetricWeight * F +
settings.roundnessMetricWeight * C +
settings.straightnessMetricWeight * P +
settings.normalSeamMetricWeight * N +
settings.textureSeamMetricWeight * T);
/*cost = settings.proxyFitMetricWeight * powf(F, settings.proxyFitMetricExponent);
cost = max(cost, settings.roundnessMetricWeight * powf(C, settings.roundnessMetricExponent));
cost = max(cost, settings.straightnessMetricWeight * pow(P, settings.straightnessMetricExponent));
cost = max(cost, settings.normalSeamMetricWeight * N);
cost = max(cost, settings.textureSeamMetricWeight * T);*/
// Enforce limits strictly:
if (newChartArea > settings.maxChartArea) cost = FLT_MAX;
if (newBoundaryLength > settings.maxBoundaryLength) cost = FLT_MAX;
// Make sure normal seams are fully respected:
if (settings.normalSeamMetricWeight >= 1000 && N != 0) cost = FLT_MAX;
nvCheck(isFinite(cost));
return cost;
}
// Returns a value in [0-1].
float AtlasBuilder::evaluateProxyFitMetric(ChartBuildData * chart, uint f)
{
const HalfEdge::Face * face = mesh->faceAt(f);
Vector3 faceNormal = triangleNormal(face);
//return square(dot(chart->coneAxis, faceNormal) - cosf(chart->coneAngle));
// Use plane fitting metric for now:
//return square(1 - dot(faceNormal, chart->planeNormal)); // @@ normal deviations should be weighted by face area
return 1 - dot(faceNormal, chart->planeNormal); // @@ normal deviations should be weighted by face area
// Find distance to chart.
/*Vector3 faceCentroid = face->centroid();
float dist = 0;
int count = 0;
for (HalfEdge::Face::ConstEdgeIterator it(face->edges()); !it.isDone(); it.advance())
{
const HalfEdge::Edge * edge = it.current();
if (!edge->isBoundary()) {
const HalfEdge::Face * neighborFace = edge->pair()->face();
if (faceChartArray[neighborFace->id()] == chart->id) {
dist += length(neighborFace->centroid() - faceCentroid);
count++;
}
}
}
dist /= (count * count);
return (1 - dot(faceNormal, chart->planeNormal)) * dist;*/
//return (1 - dot(faceNormal, chart->planeNormal));
}
float AtlasBuilder::evaluateDistanceToBoundary(ChartBuildData * chart, uint face)
{
//#pragma message(NV_FILE_LINE "TODO: Evaluate distance to boundary metric.")
// @@ This is needed for the seed relocation code.
// @@ This could provide a better roundness metric.
return 0.0f;
}
float AtlasBuilder::evaluateDistanceToSeed(ChartBuildData * chart, uint f)
{
//const uint seed = chart->seeds.back();
//const uint faceCount = mesh->faceCount();
//return shortestPaths[seed * faceCount + f];
const HalfEdge::Face * seed = mesh->faceAt(chart->seeds.back());
const HalfEdge::Face * face = mesh->faceAt(f);
return length(triangleCenter(seed) - triangleCenter(face));
}
float AtlasBuilder::evaluateRoundnessMetric(ChartBuildData * chart, uint face, float newBoundaryLength, float newChartArea)
{
// @@ D-charts use distance to seed.
// C(c,t) = pi * D(S_c,t)^2 / A_c
//return PI * square(evaluateDistanceToSeed(chart, face)) / chart->area;
//return PI * square(evaluateDistanceToSeed(chart, face)) / chart->area;
//return 2 * PI * evaluateDistanceToSeed(chart, face) / chart->boundaryLength;
// Garland's Hierarchical Face Clustering paper uses ratio between boundary and area, which is easier to compute and might work as well:
// roundness = D^2/4*pi*A -> circle = 1, non circle greater than 1
//return square(newBoundaryLength) / (newChartArea * 4 * PI);
float roundness = square(chart->boundaryLength) / chart->area;
float newRoundness = square(newBoundaryLength) / newChartArea;
if (newRoundness > roundness) {
return square(newBoundaryLength) / (newChartArea * 4 * PI);
}
else {
// Offer no impedance to faces that improve roundness.
return 0;
}
//return square(newBoundaryLength) / (4 * PI * newChartArea);
//return clamp(1 - (4 * PI * newChartArea) / square(newBoundaryLength), 0.0f, 1.0f);
// Use the ratio between the new roundness vs. the previous roundness.
// - If we use the absolute metric, when the initial face is very long, then it's hard to make any progress.
//return (square(newBoundaryLength) * chart->area) / (square(chart->boundaryLength) * newChartArea);
//return (4 * PI * newChartArea) / square(newBoundaryLength) - (4 * PI * chart->area) / square(chart->boundaryLength);
//if (square(newBoundaryLength) * chart->area) / (square(chart->boundaryLength) * newChartArea);
}
float AtlasBuilder::evaluateStraightnessMetric(ChartBuildData * chart, uint f)
{
float l_out = 0.0f;
float l_in = 0.0f;
const HalfEdge::Face * face = mesh->faceAt(f);
for (HalfEdge::Face::ConstEdgeIterator it(face->edges()); !it.isDone(); it.advance())
{
const HalfEdge::Edge * edge = it.current();
//float l = edge->length();
float l = edgeLengths[edge->id/2];
if (edge->isBoundary())
{
l_out += l;
}
else
{
uint neighborFaceId = edge->pair->face->id;
if (faceChartArray[neighborFaceId] != chart->id) {
l_out += l;
}
else {
l_in += l;
}
}
}
nvDebugCheck(l_in != 0.0f); // Candidate face must be adjacent to chart. @@ This is not true if the input mesh has zero-length edges.
//return l_out / l_in;
float ratio = (l_out - l_in) / (l_out + l_in);
//if (ratio < 0) ratio *= 10; // Encourage closing gaps.
return min(ratio, 0.0f); // Only use the straightness metric to close gaps.
//return ratio;
}
float AtlasBuilder::evaluateNormalSeamMetric(ChartBuildData * chart, uint f)
{
float seamFactor = 0.0f;
float totalLength = 0.0f;
const HalfEdge::Face * face = mesh->faceAt(f);
for (HalfEdge::Face::ConstEdgeIterator it(face->edges()); !it.isDone(); it.advance())
{
const HalfEdge::Edge * edge = it.current();
if (edge->isBoundary()) {
continue;
}
const uint neighborFaceId = edge->pair->face->id;
if (faceChartArray[neighborFaceId] != chart->id) {
continue;
}
//float l = edge->length();
float l = edgeLengths[edge->id/2];
totalLength += l;
if (!edge->isSeam()) {
continue;
}
// Make sure it's a normal seam.
if (isNormalSeam(edge))
{
float d0 = clamp(dot(edge->vertex->nor, edge->pair->next->vertex->nor), 0.0f, 1.0f);
float d1 = clamp(dot(edge->next->vertex->nor, edge->pair->vertex->nor), 0.0f, 1.0f);
//float a0 = clamp(acosf(d0) / (PI/2), 0.0f, 1.0f);
//float a1 = clamp(acosf(d1) / (PI/2), 0.0f, 1.0f);
//l *= (a0 + a1) * 0.5f;
l *= 1 - (d0 + d1) * 0.5f;
seamFactor += l;
}
}
if (seamFactor == 0) return 0.0f;
return seamFactor / totalLength;
}
float AtlasBuilder::evaluateTextureSeamMetric(ChartBuildData * chart, uint f)
{
float seamLength = 0.0f;
//float newSeamLength = 0.0f;
//float oldSeamLength = 0.0f;
float totalLength = 0.0f;
const HalfEdge::Face * face = mesh->faceAt(f);
for (HalfEdge::Face::ConstEdgeIterator it(face->edges()); !it.isDone(); it.advance())
{
const HalfEdge::Edge * edge = it.current();
/*float l = edge->length();
totalLength += l;
if (edge->isBoundary() || !edge->isSeam()) {
continue;
}
// Make sure it's a texture seam.
if (isTextureSeam(edge))
{
uint neighborFaceId = edge->pair()->face()->id();
if (faceChartArray[neighborFaceId] != chart->id) {
newSeamLength += l;
}
else {
oldSeamLength += l;
}
}*/
if (edge->isBoundary()) {
continue;
}
const uint neighborFaceId = edge->pair->face->id;
if (faceChartArray[neighborFaceId] != chart->id) {
continue;
}
//float l = edge->length();
float l = edgeLengths[edge->id/2];
totalLength += l;
if (!edge->isSeam()) {
continue;
}
// Make sure it's a texture seam.
if (isTextureSeam(edge))
{
seamLength += l;
}
}
if (seamLength == 0.0f) {
return 0.0f; // Avoid division by zero.
}
return seamLength / totalLength;
}
float AtlasBuilder::evaluateSeamMetric(ChartBuildData * chart, uint f)
{
float newSeamLength = 0.0f;
float oldSeamLength = 0.0f;
float totalLength = 0.0f;
const HalfEdge::Face * face = mesh->faceAt(f);
for (HalfEdge::Face::ConstEdgeIterator it(face->edges()); !it.isDone(); it.advance())
{
const HalfEdge::Edge * edge = it.current();
//float l = edge->length();
float l = edgeLengths[edge->id/2];
if (edge->isBoundary())
{
newSeamLength += l;
}
else
{
if (edge->isSeam())
{
uint neighborFaceId = edge->pair->face->id;
if (faceChartArray[neighborFaceId] != chart->id) {
newSeamLength += l;
}
else {
oldSeamLength += l;
}
}
}
totalLength += l;
}
return (newSeamLength - oldSeamLength) / totalLength;
}
float AtlasBuilder::evaluateChartArea(ChartBuildData * chart, uint f)
{
const HalfEdge::Face * face = mesh->faceAt(f);
//return chart->area + face->area();
return chart->area + faceAreas[face->id];
}
float AtlasBuilder::evaluateBoundaryLength(ChartBuildData * chart, uint f)
{
float boundaryLength = chart->boundaryLength;
// Add new edges, subtract edges shared with the chart.
const HalfEdge::Face * face = mesh->faceAt(f);
for (HalfEdge::Face::ConstEdgeIterator it(face->edges()); !it.isDone(); it.advance())
{
const HalfEdge::Edge * edge = it.current();
//float edgeLength = edge->length();
float edgeLength = edgeLengths[edge->id/2];
if (edge->isBoundary())
{
boundaryLength += edgeLength;
}
else
{
uint neighborFaceId = edge->pair->face->id;
if (faceChartArray[neighborFaceId] != chart->id) {
boundaryLength += edgeLength;
}
else {
boundaryLength -= edgeLength;
}
}
}
//nvDebugCheck(boundaryLength >= 0);
return max(0.0f, boundaryLength); // @@ Hack!
}
Vector3 AtlasBuilder::evaluateChartNormalSum(ChartBuildData * chart, uint f)
{
const HalfEdge::Face * face = mesh->faceAt(f);
return chart->normalSum + triangleNormalAreaScaled(face);
}
Vector3 AtlasBuilder::evaluateChartCentroidSum(ChartBuildData * chart, uint f)
{
const HalfEdge::Face * face = mesh->faceAt(f);
return chart->centroidSum + face->centroid();
}
Vector3 AtlasBuilder::computeChartCentroid(const ChartBuildData * chart)
{
Vector3 centroid(0);
const uint faceCount = chart->faces.count();
for (uint i = 0; i < faceCount; i++)
{
const HalfEdge::Face * face = mesh->faceAt(chart->faces[i]);
centroid += triangleCenter(face);
}
return centroid / float(faceCount);
}
void AtlasBuilder::fillHoles(float threshold)
{
while (facesLeft > 0)
{
createRandomChart(threshold);
}
}
void AtlasBuilder::mergeChart(ChartBuildData * owner, ChartBuildData * chart, float sharedBoundaryLength)
{
const uint faceCount = chart->faces.count();
for (uint i = 0; i < faceCount; i++)
{
uint f = chart->faces[i];
nvDebugCheck(faceChartArray[f] == chart->id);
faceChartArray[f] = owner->id;
owner->faces.append(f);
}
// Update adjacencies?
owner->area += chart->area;
owner->boundaryLength += chart->boundaryLength - sharedBoundaryLength;
owner->normalSum += chart->normalSum;
owner->centroidSum += chart->centroidSum;
updateProxy(owner);
}
void AtlasBuilder::mergeCharts()
{
Array<float> sharedBoundaryLengths;
const uint chartCount = chartArray.count();
for (int c = chartCount-1; c >= 0; c--)
{
sharedBoundaryLengths.clear();
sharedBoundaryLengths.resize(chartCount, 0.0f);
ChartBuildData * chart = chartArray[c];
float externalBoundary = 0.0f;
const uint faceCount = chart->faces.count();
for (uint i = 0; i < faceCount; i++)
{
uint f = chart->faces[i];
const HalfEdge::Face * face = mesh->faceAt(f);
for (HalfEdge::Face::ConstEdgeIterator it(face->edges()); !it.isDone(); it.advance())
{
const HalfEdge::Edge * edge = it.current();
//float l = edge->length();
float l = edgeLengths[edge->id/2];
if (edge->isBoundary()) {
externalBoundary += l;
}
else {
uint neighborFace = edge->pair->face->id;
uint neighborChart = faceChartArray[neighborFace];
if (neighborChart != c) {
if ((edge->isSeam() && (isNormalSeam(edge) || isTextureSeam(edge))) || neighborChart == -2) {
externalBoundary += l;
}
else {
sharedBoundaryLengths[neighborChart] += l;
}
}
}
}
}
for (int cc = chartCount-1; cc >= 0; cc--)
{
if (cc == c)
continue;
ChartBuildData * chart2 = chartArray[cc];
if (chart2 == NULL)
continue;
if (sharedBoundaryLengths[cc] > 0.8 * max(0.0f, chart->boundaryLength - externalBoundary)) {
// Try to avoid degenerate configurations.
if (chart2->boundaryLength > sharedBoundaryLengths[cc])
{
if (dot(chart2->planeNormal, chart->planeNormal) > -0.25) {
mergeChart(chart2, chart, sharedBoundaryLengths[cc]);
delete chart;
chartArray[c] = NULL;
break;
}
}
}
if (sharedBoundaryLengths[cc] > 0.20 * max(0.0f, chart->boundaryLength - externalBoundary)) {
// Compare proxies.
if (dot(chart2->planeNormal, chart->planeNormal) > 0) {
mergeChart(chart2, chart, sharedBoundaryLengths[cc]);
delete chart;
chartArray[c] = NULL;
break;
}
}
}
}
// Remove deleted charts.
for (int c = 0; c < I32(chartArray.count()); /*do not increment if removed*/)
{
if (chartArray[c] == NULL) {
chartArray.removeAt(c);
// Update faceChartArray.
const uint faceCount = faceChartArray.count();
for (uint i = 0; i < faceCount; i++) {
nvDebugCheck (faceChartArray[i] != -1);
nvDebugCheck (faceChartArray[i] != c);
nvDebugCheck (faceChartArray[i] <= I32(chartArray.count()));
if (faceChartArray[i] > c) {
faceChartArray[i]--;
}
}
}
else {
chartArray[c]->id = c;
c++;
}
}
}
const Array<uint> & AtlasBuilder::chartFaces(uint i) const
{
return chartArray[i]->faces;
}