/* Calculate the face or vertex normals of the current vertex data. */
void VertexData::calculateNormals()
{
#ifndef NDEBUG
int wrongNormals = 0;
#endif
normals.clear();
normals.reserve(vertices.size());
// initialize all normals to zero
for (size_t i = 0; i < vertices.size(); ++i)
normals.push_back(Normal(0, 0, 0));
// iterate over all triangles and add their normals to adjacent vertices
#pragma omp parallel for
for (ssize_t i = 0; i < ssize_t(triangles.size()); ++i)
{
const Index i0 = triangles[i][0];
const Index i1 = triangles[i][1];
const Index i2 = triangles[i][2];
const Normal normal =
vmml::compute_normal(vertices[i0], vertices[i1], vertices[i2]);
#ifndef NDEBUG
// count emtpy normals in debug mode
if (normal.length() == 0.0f)
++wrongNormals; // racy with OpenMP, but not critical
#endif
normals[i0] += normal;
normals[i1] += normal;
normals[i2] += normal;
}
// normalize all the normals
#pragma omp parallel for
for (ssize_t i = 0; i < ssize_t(vertices.size()); ++i)
normals[i].normalize();
#ifndef NDEBUG
if (wrongNormals > 0)
PLYLIBINFO << wrongNormals << " faces have no valid normal."
<< std::endl;
#endif
}
bool TriMesh::computeTangentSpaceBasis() {
int zeroArea = 0, zeroNormals = 0;
if (!m_texcoords) {
bool anisotropic = hasBSDF() && m_bsdf->getType() & BSDF::EAnisotropic;
if (anisotropic)
Log(EError, "\"%s\": computeTangentSpace(): texture coordinates "
"are required to generate tangent vectors. If you want to render with an anisotropic "
"material, please make sure that all associated shapes have valid texture coordinates.",
getName().c_str());
return false;
}
if (m_tangents)
Log(EError, "Tangent space vectors have already been generated!");
if (!m_normals) {
Log(EWarn, "Vertex normals are required to compute a tangent space basis!");
return false;
}
m_tangents = new TangentSpace[m_vertexCount];
memset(m_tangents, 0, sizeof(TangentSpace));
/* No. of triangles sharing a vertex */
uint32_t *sharers = new uint32_t[m_vertexCount];
for (size_t i=0; i<m_vertexCount; i++) {
m_tangents[i].dpdu = Vector(0.0f);
m_tangents[i].dpdv = Vector(0.0f);
if (m_normals[i].isZero()) {
zeroNormals++;
m_normals[i] = Normal(1.0f, 0.0f, 0.0f);
}
sharers[i] = 0;
}
for (size_t i=0; i<m_triangleCount; i++) {
uint32_t idx0 = m_triangles[i].idx[0],
idx1 = m_triangles[i].idx[1],
idx2 = m_triangles[i].idx[2];
const Point &v0 = m_positions[idx0];
const Point &v1 = m_positions[idx1];
const Point &v2 = m_positions[idx2];
const Point2 &uv0 = m_texcoords[idx0];
const Point2 &uv1 = m_texcoords[idx1];
const Point2 &uv2 = m_texcoords[idx2];
Vector dP1 = v1 - v0, dP2 = v2 - v0;
Vector2 dUV1 = uv1 - uv0, dUV2 = uv2 - uv0;
Float invDet = 1.0f, determinant = dUV1.x * dUV2.y - dUV1.y * dUV2.x;
if (determinant != 0)
invDet = 1.0f / determinant;
Vector dpdu = ( dUV2.y * dP1 - dUV1.y * dP2) * invDet;
Vector dpdv = (-dUV2.x * dP1 + dUV1.x * dP2) * invDet;
if (dpdu.length() == 0.0f) {
/* Recovery - required to recover from invalid geometry */
Normal n = Normal(cross(v1 - v0, v2 - v0));
Float length = n.length();
if (length != 0) {
n /= length;
dpdu = cross(n, dpdv);
if (dpdu.length() == 0.0f) {
/* At least create some kind of tangent space basis
(fair enough for isotropic BxDFs) */
coordinateSystem(n, dpdu, dpdv);
}
} else {
zeroArea++;
}
}
if (dpdv.length() == 0.0f) {
Normal n = Normal(cross(v1 - v0, v2 - v0));
Float length = n.length();
if (length != 0) {
n /= length;
dpdv = cross(dpdu, n);
if (dpdv.length() == 0.0f) {
/* At least create some kind of tangent space basis
(fair enough for isotropic BxDFs) */
coordinateSystem(n, dpdu, dpdv);
}
} else {
zeroArea++;
}
}
m_tangents[idx0].dpdu += dpdu;
m_tangents[idx1].dpdu += dpdu;
m_tangents[idx2].dpdu += dpdu;
m_tangents[idx0].dpdv += dpdv;
m_tangents[idx1].dpdv += dpdv;
m_tangents[idx2].dpdv += dpdv;
sharers[idx0]++; sharers[idx1]++; sharers[idx2]++;
}
/* Orthogonalization + Normalization pass */
for (size_t i=0; i<m_vertexCount; i++) {
Vector &dpdu = m_tangents[i].dpdu;
Vector &dpdv = m_tangents[i].dpdv;
if (dpdu.lengthSquared() == 0.0f || dpdv.lengthSquared() == 0.0f) {
/* At least create some kind of tangent space basis
(fair enough for isotropic BxDFs) */
coordinateSystem(m_normals[i], dpdu, dpdv);
} else {
if (sharers[i] > 0) {
dpdu /= (Float) sharers[i];
dpdv /= (Float) sharers[i];
}
}
}
delete[] sharers;
if (zeroArea > 0 || zeroNormals > 0)
Log(EWarn, "\"%s\": computeTangentSpace(): Mesh contains invalid "
"geometry: %i zero area triangles and %i zero normals found!",
m_name.c_str(), zeroArea, zeroNormals);
return true;
}