Geometry::Ptr
Geometry::computeTangentSpace(bool doNormals)
{
const unsigned int numVertices = this->numVertices();
if (numVertices == 0)
return shared_from_this();
if (!_data->hasProperty("position")
|| !_data->hasProperty("uv"))
throw std::logic_error("Computation of tangent space requires positions and uv.");
if (doNormals)
computeNormals();
const std::vector<unsigned short>& indices (this->indices()->data());
const unsigned int numFaces = indices.size() / 3;
unsigned short vertexIds[3] = { 0, 0, 0 };
std::vector<Vector3::Ptr> xyz(3);
std::vector<Vector2::Ptr> uv(3);
VertexBuffer::Ptr xyzBuffer = _data->get<VertexBuffer::Ptr>("position");
const unsigned int xyzSize = xyzBuffer->vertexSize();
const unsigned int xyzOffset = std::get<2>(*xyzBuffer->attribute("position"));
const std::vector<float>& xyzData = xyzBuffer->data();
VertexBuffer::Ptr uvBuffer = _data->get<VertexBuffer::Ptr>("uv");
const unsigned int uvSize = uvBuffer->vertexSize();
const unsigned int uvOffset = std::get<2>(*uvBuffer->attribute("uv"));
const std::vector<float>& uvData = uvBuffer->data();
std::vector<float> tangentsData(3 * numVertices, 0.0f);
for (unsigned int i = 0, offset = 0; i < numFaces; ++i)
{
for (unsigned int k = 0; k < 3; ++k)
{
vertexIds[k] = indices[offset++];
unsigned int index = xyzOffset + vertexIds[k] * xyzSize;
xyz[k] = Vector3::create(xyzData[index], xyzData[index + 1], xyzData[index + 2]);
index = uvOffset + vertexIds[k] * uvSize;
uv[k] = Vector2::create(uvData[index], uvData[index + 1]);
}
Vector2::Ptr uv02 = uv[0] - uv[2];
Vector2::Ptr uv12 = uv[1] - uv[2];
const float denom = uv02->x() * uv12->y() - uv12->x() * uv02->y();
const float invDenom = fabsf(denom) > 1e-6f ? 1.0f/denom : 1.0f;
Vector3::Ptr faceTangent = ((xyz[0]-xyz[2]) * uv12->y() - (xyz[1]-xyz[2]) * uv02->y()) * invDenom;
for (unsigned int k=0; k<3; ++k)
{
const unsigned int index = 3 * vertexIds[k];
tangentsData[index] += faceTangent->x();
tangentsData[index + 1] += faceTangent->y();
tangentsData[index + 2] += faceTangent->z();
}
}
for (unsigned int i = 0, index = 0; i < numVertices; ++i, index += 3)
{
const float x = tangentsData[index];
const float y = tangentsData[index + 1];
const float z = tangentsData[index + 2];
const float lengthSquared = x * x + y * y + z * z;
const float invLength = lengthSquared > 1e-6f ? 1.0f / sqrtf(lengthSquared) : 1.0f;
tangentsData[index] *= invLength;
tangentsData[index + 1] *= invLength;
tangentsData[index + 2] *= invLength;
}
VertexBuffer::Ptr tangentsBuffer = VertexBuffer::create(xyzBuffer->context(), tangentsData);
tangentsBuffer->addAttribute("tangent", 3, 0);
addVertexBuffer(tangentsBuffer);
return shared_from_this();
}
Geometry::Ptr
Geometry::computeNormals()
{
const unsigned int numVertices = this->numVertices();
if (numVertices == 0)
return shared_from_this();
if (_data->hasProperty("normal"))
throw std::logic_error("The geometry already stores precomputed normals.");
if (!_data->hasProperty("position"))
throw std::logic_error("Computation of normals requires positions.");
const std::vector<unsigned short>& indices = this->indices()->data();
const unsigned int numFaces = indices.size() / 3;
unsigned short vertexIds[3] = { 0, 0, 0 };
std::vector<Vector3::Ptr> xyz(3);
VertexBuffer::Ptr xyzBuffer = _data->get<VertexBuffer::Ptr>("position");
const unsigned int xyzSize = xyzBuffer->vertexSize();
const unsigned int xyzOffset = std::get<2>(*xyzBuffer->attribute("position"));
const std::vector<float>& xyzData = xyzBuffer->data();
std::vector<float> normalsData(3 * numVertices, 0.0f);
for (unsigned int i = 0, offset = 0; i < numFaces; ++i)
{
for (unsigned int k = 0; k < 3; ++k)
{
vertexIds[k] = indices[offset++];
const unsigned int index = xyzOffset + vertexIds[k] * xyzSize;
xyz[k] = Vector3::create(xyzData[index], xyzData[index + 1], xyzData[index + 2]);
}
Vector3::Ptr faceNormal = Vector3::create()
->copyFrom(xyz[0] - xyz[1])
->cross(xyz[0] - xyz[2]);
for (unsigned int k = 0; k < 3; ++k)
{
const unsigned int index = 3 * vertexIds[k];
normalsData[index] += faceNormal->x();
normalsData[index + 1] += faceNormal->y();
normalsData[index + 2] += faceNormal->z();
}
}
for (unsigned int i = 0, index = 0; i < numVertices; ++i, index += 3)
{
const float x = normalsData[index];
const float y = normalsData[index + 1];
const float z = normalsData[index + 2];
const float lengthSquared = x * x + y * y + z * z;
const float invLength = lengthSquared > 1e-6f ? 1.0f / sqrtf(lengthSquared) : 1.0f;
normalsData[index] *= invLength;
normalsData[index + 1] *= invLength;
normalsData[index + 2] *= invLength;
}
VertexBuffer::Ptr normalsBuffer = VertexBuffer::create(xyzBuffer->context(), normalsData);
normalsBuffer->addAttribute("normal", 3, 0);
addVertexBuffer(normalsBuffer);
return shared_from_this();
}