Bad Point Transformation using Matrix (Direct3D) - c++

Question

My problem is a little bit extense. I'm trying to print a sprite using DirectX 11 and to handle the scale and rotations I use a transformation matrix. I extracted this code from SFML, an open-source library, and for the translation works fine. However, the rotation and scale aren't working as expected as I show next.
When I rotate across the center all is correct.
When I move the sprite and then I rotate, the sprite rotates around an "unknown" point.
The same happens when I scale the sprite, it scales himself from an "unknown" point.
If I rotate the sprite, then the translation axis is the same but with the sprite rotated, so I can't move it properly.
I leave you here a little video of exactly what's going on. [VIDEO]
I think the problem is related to how I transform the sprite, but I can't assure it. I leave you here the code parts I think are involved in this error but you also can take a look into the GitHub project to take a deep look. [GITHUB PROJECT]
Transformable.cpp
const Transform& Transformable::GetTransform() const
{
if (_transformNeedUpdate)
{
float angle = -_rotation * 3.141592654f / 180.f;
float cosine = static_cast<float>(std::cos(angle));
float sine = static_cast<float>(std::sin(angle));
float sxc = _scale.x * cosine;
float syc = _scale.y * cosine;
float sxs = _scale.x * sine;
float sys = _scale.y * sine;
float tx = -_origin.x * sxc - _origin.y * sys + _position.x;
float ty = _origin.x * sxs - _origin.y * syc + _position.y;
_transform = Transform(sxc, sys, tx,
-sxs, syc, ty,
0.f, 0.f, 1.f);
_transformNeedUpdate = false;
}
return _transform;
}
Transform.cpp
Transform::Transform(
float a00, float a01, float a02,
float a10, float a11, float a12,
float a20, float a21, float a22
)
{
_matrix[0] = a00; _matrix[4] = a01; _matrix[8] = 0.f; _matrix[12] = a02;
_matrix[1] = a10; _matrix[5] = a11; _matrix[9] = 0.f; _matrix[13] = a12;
_matrix[2] = 0.f; _matrix[6] = 0.f; _matrix[10] = 1.f; _matrix[14] = 0.f;
_matrix[3] = a20; _matrix[7] = a21; _matrix[11] = 0.f; _matrix[15] = a22;
}
D3DXVECTOR2 Transform::TransformPoint(float x, float y) const
{
return D3DXVECTOR2(_matrix[0] * x + _matrix[4] * y + _matrix[12],
_matrix[1] * x + _matrix[5] * y + _matrix[13]);
}
D3DXVECTOR2 operator *(const Transform& left, const D3DXVECTOR2& right)
{
return left.TransformPoint(right);
}
Bitmap.cpp (Where I setup the vertex to be drawn)
HRESULT Bitmap::UpdateBuffers(ID3D11DeviceContext* deviceContext)
{
if (_transform == _previousTransform && _bounds == _previousBounds)
{
return S_OK;
}
VertexType* vertices;
D3D11_MAPPED_SUBRESOURCE mappedResource;
VertexType* verticesPtr;
HRESULT result;
_previousTransform = _transform;
_previousBounds = _bounds;
vertices = new VertexType[_vertexCount];
if (!vertices)
{
return CO_E_ERRORINAPP;
}
float left = _bounds.left();
float right = left + _bounds.width();
float top = _bounds.top();
float bottom = top + _bounds.height();
D3DXVECTOR2 topLeft = { left, top };
D3DXVECTOR2 bottomRight = { right, bottom };
D3DXVECTOR2 topRight = { right, top };
D3DXVECTOR2 bottomLeft = { left, bottom };
topLeft = _transform * topLeft;
bottomRight = _transform * bottomRight;
topRight = _transform * topRight;
bottomLeft = _transform * bottomLeft;
vertices[0].position = D3DXVECTOR3(topLeft.x, topLeft.y, 0.0f);
vertices[0].texture = D3DXVECTOR2(0.0f, 0.0f);
vertices[1].position = D3DXVECTOR3(bottomRight.x, bottomRight.y, 0.0f);
vertices[1].texture = D3DXVECTOR2(1.0f, 1.0f);
vertices[2].position = D3DXVECTOR3(bottomLeft.x, bottomLeft.y, 0.0f);
vertices[2].texture = D3DXVECTOR2(0.0f, 1.0f);
vertices[3].position = D3DXVECTOR3(topLeft.x, topLeft.y, 0.0f);
vertices[3].texture = D3DXVECTOR2(0.0f, 0.0f);
vertices[4].position = D3DXVECTOR3(topRight.x, topRight.y, 0.0f);
vertices[4].texture = D3DXVECTOR2(1.0f, 0.0f);
vertices[5].position = D3DXVECTOR3(bottomRight.x, bottomRight.y, 0.0f);
vertices[5].texture = D3DXVECTOR2(1.0f, 1.0f);
result = deviceContext->Map(_vertexBuffer, 0, D3D11_MAP_WRITE_DISCARD, 0, &mappedResource);
if (FAILED(result))
{
return CO_E_ERRORINAPP;
}
verticesPtr = (VertexType*)mappedResource.pData;
memcpy(verticesPtr, (void*)vertices, (sizeof(VertexType) * _vertexCount));
deviceContext->Unmap(_vertexBuffer, 0);
delete[] vertices;
vertices = 0;
return S_OK;
}
The Coordinate System is like the shown in the image below; the center of the screen is the (0,0) position.
The code flow
When the position, scale, rotation or origin of the actor changes, a new Transform is generated. Then, I transform the local bounds of the actor with the generated transform to get the correct positions of the vertex, and I set them into the vertex buffer.