Hi Robert,
In many game engines it is common to set the W component of the tangent
vector to -1 if the UVs are mirrored and 1 if not. I've updated the
osgUtil::TangentSpaceGenerator class to do the same.
Cheers,
Farshid
#include <osgUtil/TangentSpaceGenerator>
#include <osg/Notify>
#include <osg/io_utils>
using namespace osgUtil;
TangentSpaceGenerator::TangentSpaceGenerator()
: osg::Referenced(),
T_(new osg::Vec4Array),
B_(new osg::Vec4Array),
N_(new osg::Vec4Array)
{
T_->setBinding(osg::Geometry::BIND_PER_VERTEX); T_->setNormalize(false);
B_->setBinding(osg::Geometry::BIND_PER_VERTEX); T_->setNormalize(false);
N_->setBinding(osg::Geometry::BIND_PER_VERTEX); T_->setNormalize(false);
}
TangentSpaceGenerator::TangentSpaceGenerator(const TangentSpaceGenerator ©, const osg::CopyOp ©op)
: osg::Referenced(copy),
T_(static_cast<osg::Vec4Array *>(copyop(copy.T_.get()))),
B_(static_cast<osg::Vec4Array *>(copyop(copy.B_.get()))),
N_(static_cast<osg::Vec4Array *>(copyop(copy.N_.get())))
{
}
void TangentSpaceGenerator::generate(osg::Geometry *geo, int normal_map_tex_unit)
{
const osg::Array *vx = geo->getVertexArray();
const osg::Array *nx = geo->getNormalArray();
const osg::Array *tx = geo->getTexCoordArray(normal_map_tex_unit);
if (!vx || !tx) return;
unsigned int vertex_count = vx->getNumElements();
T_->assign(vertex_count, osg::Vec4());
B_->assign(vertex_count, osg::Vec4());
N_->assign(vertex_count, osg::Vec4());
unsigned int i; // VC6 doesn't like for-scoped variables
for (unsigned int pri=0; pri<geo->getNumPrimitiveSets(); ++pri) {
osg::PrimitiveSet *pset = geo->getPrimitiveSet(pri);
unsigned int N = pset->getNumIndices();
switch (pset->getMode()) {
case osg::PrimitiveSet::TRIANGLES:
for (i=0; i<N; i+=3) {
compute(pset, vx, nx, tx, i, i+1, i+2);
}
break;
case osg::PrimitiveSet::QUADS:
for (i=0; i<N; i+=4) {
compute(pset, vx, nx, tx, i, i+1, i+2);
compute(pset, vx, nx, tx, i+2, i+3, i);
}
break;
case osg::PrimitiveSet::TRIANGLE_STRIP:
if (pset->getType() == osg::PrimitiveSet::DrawArrayLengthsPrimitiveType) {
osg::DrawArrayLengths *dal = static_cast<osg::DrawArrayLengths *>(pset);
unsigned int j = 0;
for (osg::DrawArrayLengths::const_iterator pi=dal->begin(); pi!=dal->end(); ++pi) {
unsigned int iN = static_cast<unsigned int>(*pi-2);
for (i=0; i<iN; ++i, ++j) {
if ((i%2) == 0) {
compute(pset, vx, nx, tx, j, j+1, j+2);
} else {
compute(pset, vx, nx, tx, j+1, j, j+2);
}
}
j += 2;
}
} else {
for (i=0; i<N-2; ++i) {
if ((i%2) == 0) {
compute(pset, vx, nx, tx, i, i+1, i+2);
} else {
compute(pset, vx, nx, tx, i+1, i, i+2);
}
}
}
break;
case osg::PrimitiveSet::QUAD_STRIP:
if (pset->getType() == osg::PrimitiveSet::DrawArrayLengthsPrimitiveType) {
osg::DrawArrayLengths *dal = static_cast<osg::DrawArrayLengths *>(pset);
unsigned int j = 0;
for (osg::DrawArrayLengths::const_iterator pi=dal->begin(); pi!=dal->end(); ++pi) {
unsigned int iN = static_cast<unsigned int>(*pi-2);
for (i=0; i<iN; ++i, ++j) {
if ((i%2) == 0) {
compute(pset, vx, nx, tx, j, j+2, j+1);
} else {
compute(pset, vx, nx, tx, j, j+1, j+2);
}
}
j += 2;
}
} else {
for (i=0; i<N-2; ++i) {
if ((i%2) == 0) {
compute(pset, vx, nx, tx, i, i+2, i+1);
} else {
compute(pset, vx, nx, tx, i, i+1, i+2);
}
}
}
break;
case osg::PrimitiveSet::TRIANGLE_FAN:
case osg::PrimitiveSet::POLYGON:
if (pset->getType() == osg::PrimitiveSet::DrawArrayLengthsPrimitiveType) {
osg::DrawArrayLengths *dal = static_cast<osg::DrawArrayLengths *>(pset);
unsigned int j = 0;
for (osg::DrawArrayLengths::const_iterator pi=dal->begin(); pi!=dal->end(); ++pi) {
unsigned int iN = static_cast<unsigned int>(*pi-2);
for (i=0; i<iN; ++i) {
compute(pset, vx, nx, tx, 0, j+1, j+2);
}
j += 2;
}
} else {
for (i=0; i<N-2; ++i) {
compute(pset, vx, nx, tx, 0, i+1, i+2);
}
}
break;
case osg::PrimitiveSet::POINTS:
case osg::PrimitiveSet::LINES:
case osg::PrimitiveSet::LINE_STRIP:
case osg::PrimitiveSet::LINE_LOOP:
case osg::PrimitiveSet::LINES_ADJACENCY:
case osg::PrimitiveSet::LINE_STRIP_ADJACENCY:
break;
default: OSG_WARN << "Warning: TangentSpaceGenerator: unknown primitive mode " << pset->getMode() << "\n";
}
}
// normalize basis vectors and force the normal vector to match
// the triangle normal's direction
unsigned int attrib_count = vx->getNumElements();
for (i=0; i<attrib_count; ++i) {
osg::Vec4 &vT = (*T_)[i];
osg::Vec4 &vB = (*B_)[i];
osg::Vec4 &vN = (*N_)[i];
osg::Vec3 txN = osg::Vec3(vT.x(), vT.y(), vT.z()) ^ osg::Vec3(vB.x(), vB.y(), vB.z());
bool flipped = txN * osg::Vec3(vN.x(), vN.y(), vN.z()) < 0;
if (flipped) {
vN = osg::Vec4(-txN, 0);
} else {
vN = osg::Vec4(txN, 0);
}
vT.normalize();
vB.normalize();
vN.normalize();
vT[3] = flipped ? -1.0f : 1.0f;
}
/* TO-DO: if indexed, compress the attributes to have only one
* version of each (different indices for each one?) */
}
void TangentSpaceGenerator::compute(osg::PrimitiveSet *pset,
const osg::Array* vx,
const osg::Array* nx,
const osg::Array* tx,
int iA, int iB, int iC)
{
iA = pset->index(iA);
iB = pset->index(iB);
iC = pset->index(iC);
osg::Vec3 P1;
osg::Vec3 P2;
osg::Vec3 P3;
int i; // VC6 doesn't like for-scoped variables
switch (vx->getType())
{
case osg::Array::Vec2ArrayType:
for (i=0; i<2; ++i) {
P1.ptr()[i] = static_cast<const osg::Vec2Array&>(*vx)[iA].ptr()[i];
P2.ptr()[i] = static_cast<const osg::Vec2Array&>(*vx)[iB].ptr()[i];
P3.ptr()[i] = static_cast<const osg::Vec2Array&>(*vx)[iC].ptr()[i];
}
break;
case osg::Array::Vec3ArrayType:
P1 = static_cast<const osg::Vec3Array&>(*vx)[iA];
P2 = static_cast<const osg::Vec3Array&>(*vx)[iB];
P3 = static_cast<const osg::Vec3Array&>(*vx)[iC];
break;
case osg::Array::Vec4ArrayType:
for (i=0; i<3; ++i) {
P1.ptr()[i] = static_cast<const osg::Vec4Array&>(*vx)[iA].ptr()[i];
P2.ptr()[i] = static_cast<const osg::Vec4Array&>(*vx)[iB].ptr()[i];
P3.ptr()[i] = static_cast<const osg::Vec4Array&>(*vx)[iC].ptr()[i];
}
break;
default:
OSG_WARN << "Warning: TangentSpaceGenerator: vertex array must be Vec2Array, Vec3Array or Vec4Array" << std::endl;
}
osg::Vec3 N1;
osg::Vec3 N2;
osg::Vec3 N3;
if(nx)
{
switch (nx->getType())
{
case osg::Array::Vec2ArrayType:
for (i=0; i<2; ++i) {
N1.ptr()[i] = static_cast<const osg::Vec2Array&>(*nx)[iA].ptr()[i];
N2.ptr()[i] = static_cast<const osg::Vec2Array&>(*nx)[iB].ptr()[i];
N3.ptr()[i] = static_cast<const osg::Vec2Array&>(*nx)[iC].ptr()[i];
}
break;
case osg::Array::Vec3ArrayType:
N1 = static_cast<const osg::Vec3Array&>(*nx)[iA];
N2 = static_cast<const osg::Vec3Array&>(*nx)[iB];
N3 = static_cast<const osg::Vec3Array&>(*nx)[iC];
break;
case osg::Array::Vec4ArrayType:
for (i=0; i<3; ++i) {
N1.ptr()[i] = static_cast<const osg::Vec4Array&>(*nx)[iA].ptr()[i];
N2.ptr()[i] = static_cast<const osg::Vec4Array&>(*nx)[iB].ptr()[i];
N3.ptr()[i] = static_cast<const osg::Vec4Array&>(*nx)[iC].ptr()[i];
}
break;
default:
OSG_WARN << "Warning: TangentSpaceGenerator: normal array must be Vec2Array, Vec3Array or Vec4Array" << std::endl;
}
}
osg::Vec2 uv1;
osg::Vec2 uv2;
osg::Vec2 uv3;
switch (tx->getType())
{
case osg::Array::Vec2ArrayType:
uv1 = static_cast<const osg::Vec2Array&>(*tx)[iA];
uv2 = static_cast<const osg::Vec2Array&>(*tx)[iB];
uv3 = static_cast<const osg::Vec2Array&>(*tx)[iC];
break;
case osg::Array::Vec3ArrayType:
for (i=0; i<2; ++i) {
uv1.ptr()[i] = static_cast<const osg::Vec3Array&>(*tx)[iA].ptr()[i];
uv2.ptr()[i] = static_cast<const osg::Vec3Array&>(*tx)[iB].ptr()[i];
uv3.ptr()[i] = static_cast<const osg::Vec3Array&>(*tx)[iC].ptr()[i];
}
break;
case osg::Array::Vec4ArrayType:
for (i=0; i<2; ++i) {
uv1.ptr()[i] = static_cast<const osg::Vec4Array&>(*tx)[iA].ptr()[i];
uv2.ptr()[i] = static_cast<const osg::Vec4Array&>(*tx)[iB].ptr()[i];
uv3.ptr()[i] = static_cast<const osg::Vec4Array&>(*tx)[iC].ptr()[i];
}
break;
default:
OSG_WARN << "Warning: TangentSpaceGenerator: texture coord array must be Vec2Array, Vec3Array or Vec4Array" << std::endl;
}
if(nx){
osg::Vec3 V, T1, T2, T3, B1, B2, B3;
V = osg::Vec3(P2.x() - P1.x(), uv2.x() - uv1.x(), uv2.y() - uv1.y()) ^
osg::Vec3(P3.x() - P1.x(), uv3.x() - uv1.x(), uv3.y() - uv1.y());
if (V.x() != 0) {
V.normalize();
T1.x() += -V.y() / V.x();
B1.x() += -V.z() / V.x();
T2.x() += -V.y() / V.x();
B2.x() += -V.z() / V.x();
T3.x() += -V.y() / V.x();
B3.x() += -V.z() / V.x();
}
V = osg::Vec3(P2.y() - P1.y(), uv2.x() - uv1.x(), uv2.y() - uv1.y()) ^
osg::Vec3(P3.y() - P1.y(), uv3.x() - uv1.x(), uv3.y() - uv1.y());
if (V.x() != 0) {
V.normalize();
T1.y() += -V.y() / V.x();
B1.y() += -V.z() / V.x();
T2.y() += -V.y() / V.x();
B2.y() += -V.z() / V.x();
T3.y() += -V.y() / V.x();
B3.y() += -V.z() / V.x();
}
V = osg::Vec3(P2.z() - P1.z(), uv2.x() - uv1.x(), uv2.y() - uv1.y()) ^
osg::Vec3(P3.z() - P1.z(), uv3.x() - uv1.x(), uv3.y() - uv1.y());
if (V.x() != 0) {
V.normalize();
T1.z() += -V.y() / V.x();
B1.z() += -V.z() / V.x();
T2.z() += -V.y() / V.x();
B2.z() += -V.z() / V.x();
T3.z() += -V.y() / V.x();
B3.z() += -V.z() / V.x();
}
osg::Vec3 tempvec;
tempvec = N1 ^ T1;
(*T_)[iA] = osg::Vec4(tempvec ^ N1, 0);
tempvec = B1 ^ N1;
(*B_)[iA] = osg::Vec4(N1 ^ tempvec, 0);
tempvec = N2 ^ T2;
(*T_)[iB] = osg::Vec4(tempvec ^ N2, 0);
tempvec = B2 ^ N2;
(*B_)[iB] = osg::Vec4(N2 ^ tempvec, 0);
tempvec = N3 ^ T3;
(*T_)[iC] = osg::Vec4(tempvec ^ N3, 0);
tempvec = B3 ^ N3;
(*B_)[iC] = osg::Vec4(N3 ^ tempvec, 0);
(*N_)[iA] += osg::Vec4(N1, 0);
(*N_)[iB] += osg::Vec4(N2, 0);
(*N_)[iC] += osg::Vec4(N3, 0);
}
else{
osg::Vec3 face_normal = (P2 - P1) ^ (P3 - P1);
osg::Vec3 V;
V = osg::Vec3(P2.x() - P1.x(), uv2.x() - uv1.x(), uv2.y() - uv1.y()) ^
osg::Vec3(P3.x() - P1.x(), uv3.x() - uv1.x(), uv3.y() - uv1.y());
if (V.x() != 0) {
V.normalize();
(*T_)[iA].x() += -V.y() / V.x();
(*B_)[iA].x() += -V.z() / V.x();
(*T_)[iB].x() += -V.y() / V.x();
(*B_)[iB].x() += -V.z() / V.x();
(*T_)[iC].x() += -V.y() / V.x();
(*B_)[iC].x() += -V.z() / V.x();
}
V = osg::Vec3(P2.y() - P1.y(), uv2.x() - uv1.x(), uv2.y() - uv1.y()) ^
osg::Vec3(P3.y() - P1.y(), uv3.x() - uv1.x(), uv3.y() - uv1.y());
if (V.x() != 0) {
V.normalize();
(*T_)[iA].y() += -V.y() / V.x();
(*B_)[iA].y() += -V.z() / V.x();
(*T_)[iB].y() += -V.y() / V.x();
(*B_)[iB].y() += -V.z() / V.x();
(*T_)[iC].y() += -V.y() / V.x();
(*B_)[iC].y() += -V.z() / V.x();
}
V = osg::Vec3(P2.z() - P1.z(), uv2.x() - uv1.x(), uv2.y() - uv1.y()) ^
osg::Vec3(P3.z() - P1.z(), uv3.x() - uv1.x(), uv3.y() - uv1.y());
if (V.x() != 0) {
V.normalize();
(*T_)[iA].z() += -V.y() / V.x();
(*B_)[iA].z() += -V.z() / V.x();
(*T_)[iB].z() += -V.y() / V.x();
(*B_)[iB].z() += -V.z() / V.x();
(*T_)[iC].z() += -V.y() / V.x();
(*B_)[iC].z() += -V.z() / V.x();
}
(*N_)[iA] += osg::Vec4(face_normal, 0);
(*N_)[iB] += osg::Vec4(face_normal, 0);
(*N_)[iC] += osg::Vec4(face_normal, 0);
}
}
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