法线、平面、顶点、数学
第一天,神说要有math,要计算法线,于是就有了Ogre::math,有了法线计算。
/**/
/** Calculate a face normal, including the w component which is the offset from the origin. */
static Vector4 calculateFaceNormal( const Vector3 & v1, const Vector3 & v2, const Vector3 & v3);
/**/ /** Calculate a face normal, no w-information. */
static Vector3 calculateBasicFaceNormal( const Vector3 & v1, const Vector3 & v2, const Vector3 & v3);
/**/ /** Calculate a face normal without normalize, including the w component which is the offset from the origin. */
static Vector4 calculateFaceNormalWithoutNormalize( const Vector3 & v1, const Vector3 & v2, const Vector3 & v3);
/**/ /** Calculate a face normal without normalize, no w-information. */
static Vector3 calculateBasicFaceNormalWithoutNormalize( const Vector3 & v1, const Vector3 & v2, const Vector3 & v3);
文如其名,四个上帝之子是同胞胎,只为了一个目的:得到法线,和一个附加长度。
static Vector4 calculateFaceNormal( const Vector3 & v1, const Vector3 & v2, const Vector3 & v3);
/**/ /** Calculate a face normal, no w-information. */
static Vector3 calculateBasicFaceNormal( const Vector3 & v1, const Vector3 & v2, const Vector3 & v3);
/**/ /** Calculate a face normal without normalize, including the w component which is the offset from the origin. */
static Vector4 calculateFaceNormalWithoutNormalize( const Vector3 & v1, const Vector3 & v2, const Vector3 & v3);
/**/ /** Calculate a face normal without normalize, no w-information. */
static Vector3 calculateBasicFaceNormalWithoutNormalize( const Vector3 & v1, const Vector3 & v2, const Vector3 & v3);
//
-----------------------------------------------------------------------
Vector4 Math::calculateFaceNormal( const Vector3 & v1, const Vector3 & v2, const Vector3 & v3)
{
Vector3 normal = calculateBasicFaceNormal(v1, v2, v3);
// Now set up the w (distance of tri from origin
return Vector4(normal.x, normal.y, normal.z, -(normal.dotProduct(v1)));
}
// -----------------------------------------------------------------------
Vector3 Math::calculateBasicFaceNormal( const Vector3 & v1, const Vector3 & v2, const Vector3 & v3)
{
Vector3 normal = (v2 - v1).crossProduct(v3 - v1);
normal.normalise();
return normal;
}
// -----------------------------------------------------------------------
Vector4 Math::calculateFaceNormalWithoutNormalize( const Vector3 & v1, const Vector3 & v2, const Vector3 & v3)
{
Vector3 normal = calculateBasicFaceNormalWithoutNormalize(v1, v2, v3);
// Now set up the w (distance of tri from origin)
return Vector4(normal.x, normal.y, normal.z, -(normal.dotProduct(v1)));
}
// -----------------------------------------------------------------------
Vector3 Math::calculateBasicFaceNormalWithoutNormalize( const Vector3 & v1, const Vector3 & v2, const Vector3 & v3)
{
Vector3 normal = (v2 - v1).crossProduct(v3 - v1);
return normal;
}
上帝是多么的英明,在你千辛万苦google后却还是无果的时候,却发现圣书上古老的笔迹是最好的诠释。
Vector4 Math::calculateFaceNormal( const Vector3 & v1, const Vector3 & v2, const Vector3 & v3)
{
Vector3 normal = calculateBasicFaceNormal(v1, v2, v3);
// Now set up the w (distance of tri from origin
return Vector4(normal.x, normal.y, normal.z, -(normal.dotProduct(v1)));
}
// -----------------------------------------------------------------------
Vector3 Math::calculateBasicFaceNormal( const Vector3 & v1, const Vector3 & v2, const Vector3 & v3)
{
Vector3 normal = (v2 - v1).crossProduct(v3 - v1);
normal.normalise();
return normal;
}
// -----------------------------------------------------------------------
Vector4 Math::calculateFaceNormalWithoutNormalize( const Vector3 & v1, const Vector3 & v2, const Vector3 & v3)
{
Vector3 normal = calculateBasicFaceNormalWithoutNormalize(v1, v2, v3);
// Now set up the w (distance of tri from origin)
return Vector4(normal.x, normal.y, normal.z, -(normal.dotProduct(v1)));
}
// -----------------------------------------------------------------------
Vector3 Math::calculateBasicFaceNormalWithoutNormalize( const Vector3 & v1, const Vector3 & v2, const Vector3 & v3)
{
Vector3 normal = (v2 - v1).crossProduct(v3 - v1);
return normal;
}
第二天,上帝走在水面上,说要有一个面,于是就有了平面。
Ogre::MeshManager::getSingleton().createPlane(
"
floor
"
, Ogre::ResourceGroupManager::DEFAULT_RESOURCE_GROUP_NAME,
Plane(Vector3::UNIT_Y, 0 ), 200 , 200 , 10 , 10 , true , 1 , 10 , 10 , Vector3::UNIT_Z);
// create a floor entity, give it a material, and place it at the origin
Ogre::Entity * floor = mSceneMgr -> createEntity( " Floor " , " floor " );
floor -> setMaterialName( " Examples/Rockwall " );
floor -> setCastShadows( false );
mSceneMgr -> getRootSceneNode() -> attachObject(floor);
Plane(Vector3::UNIT_Y, 0 ), 200 , 200 , 10 , 10 , true , 1 , 10 , 10 , Vector3::UNIT_Z);
// create a floor entity, give it a material, and place it at the origin
Ogre::Entity * floor = mSceneMgr -> createEntity( " Floor " , " floor " );
floor -> setMaterialName( " Examples/Rockwall " );
floor -> setCastShadows( false );
mSceneMgr -> getRootSceneNode() -> attachObject(floor);
第三天,神说要有点、也要有叉。点点叉叉才像世界。
1).点积维基: http://en.wikipedia.org/wiki/Dot_product
点积没有其他的几何意义,除了表示2个向量的角度:
同时在ogre代码中:
inline Real Vector3::dotProduct(
const
Vector3
&
vec)
const
{
return x * vec.x + y * vec.y + z * vec.z;
}
{
return x * vec.x + y * vec.y + z * vec.z;
}
这里也可以看到一个互动效果的点积图形程序:
http://xahlee.org/SpecialPlaneCurves_dir/ggb/Vector_Dot_Product.html
也可以看到在其他领域点积还是有意义的,例如物理
2).叉积
维基: http://en.wikipedia.org/wiki/Cross_product
叉积的结果正好是面的法线向量。这个向量的绝对值正好是向量包围体的体积\面积。
叉积的结果表示:
同时在ogre代码中:
inline Vector3::Vector3 crossProduct(
const
Vector3
&
rkVector )
const
{
return Vector3(
y * rkVector.z - z * rkVector.y,
z * rkVector.x - x * rkVector.z,
x * rkVector.y - y * rkVector.x);
}
{
return Vector3(
y * rkVector.z - z * rkVector.y,
z * rkVector.x - x * rkVector.z,
x * rkVector.y - y * rkVector.x);
}
3).四元数
一个四元数可以对应一个4*4矩阵,这是上帝的法则,作为它的子民,只有依其言行事。
这里你可以看到四元数---对应矩阵---模型的互动操作,I love It!当然,只板樯才可以让演示程序跑起来,I 罚克中国恭馋裤裆。
http://www.euclideanspace.com/maths/geometry/rotations/conversions/quaternionToMatrix/program/index.htm
这个站还有四元数相关运算的详细推导,例如四元数转4*4矩阵。
4).矩阵
- Martin Baker's All-Inclusive Learning Site
- A Simple Quaternion-based Camera
- Matrix and Quaternion FAQ
第四天,上帝想考验世人的信仰,想看看每一颗心是不是红的。
Entity
*
ent
=
NULL;
// mesh data to retrieve
size_t vertex_count;
size_t index_count;
Ogre::Vector3 * vertices;
unsigned long * indices;
// get the mesh information
GetMeshInformation(ent -> getMesh(), vertex_count, vertices, index_count, indices,
ent -> getParentNode() -> _getDerivedPosition(),
ent -> getParentNode() -> _getDerivedOrientation(),
ent -> getParentNode() -> getScale());
// test for hitting individual triangles on the mesh
for ( int i = 0 ; i < static_cast < int > (index_count); i += 3 )
{
// check for a hit against this triangle
//std::pair<bool, Ogre::Real> hit = Ogre::Math::intersects(ray, vertices[indices[i]],
// vertices[indices[i+1]], vertices[indices[i+2]], true, false);
Vector3 noraml = Ogre::Math::calculateBasicFaceNormalWithoutNormalize (vertices[indices[i]], vertices[indices[i+1]], vertices[indices[i+2]] );
Vector3 center = (vertices[indices[i]] + vertices[indices[i+1]])/2;
center = (center+vertices[indices[i+2]] )/2;
mPoints.push_back(center);
mPoints.push_back(center + noraml );
}
// free the verticies and indicies memory
delete[] vertices;
delete[] indices;
/**/ ///////////////////////////////////////////////////////////////////////
// Get the mesh information for the given mesh.
// Code found on this forum link: http://www.ogre3d.org/wiki/index.php/RetrieveVertexData
void DynLine::GetMeshInformation( const Ogre::MeshPtr mesh,
size_t & vertex_count,
Ogre::Vector3 * & vertices,
size_t & index_count,
unsigned long * & indices,
const Ogre::Vector3 & position,
const Ogre::Quaternion & orient,
const Ogre::Vector3 & scale)
// mesh data to retrieve
size_t vertex_count;
size_t index_count;
Ogre::Vector3 * vertices;
unsigned long * indices;
// get the mesh information
GetMeshInformation(ent -> getMesh(), vertex_count, vertices, index_count, indices,
ent -> getParentNode() -> _getDerivedPosition(),
ent -> getParentNode() -> _getDerivedOrientation(),
ent -> getParentNode() -> getScale());
// test for hitting individual triangles on the mesh
for ( int i = 0 ; i < static_cast < int > (index_count); i += 3 )
{
// check for a hit against this triangle
//std::pair<bool, Ogre::Real> hit = Ogre::Math::intersects(ray, vertices[indices[i]],
// vertices[indices[i+1]], vertices[indices[i+2]], true, false);
Vector3 noraml = Ogre::Math::calculateBasicFaceNormalWithoutNormalize (vertices[indices[i]], vertices[indices[i+1]], vertices[indices[i+2]] );
Vector3 center = (vertices[indices[i]] + vertices[indices[i+1]])/2;
center = (center+vertices[indices[i+2]] )/2;
mPoints.push_back(center);
mPoints.push_back(center + noraml );
}
// free the verticies and indicies memory
delete[] vertices;
delete[] indices;
/**/ ///////////////////////////////////////////////////////////////////////
// Get the mesh information for the given mesh.
// Code found on this forum link: http://www.ogre3d.org/wiki/index.php/RetrieveVertexData
void DynLine::GetMeshInformation( const Ogre::MeshPtr mesh,
size_t & vertex_count,
Ogre::Vector3 * & vertices,
size_t & index_count,
unsigned long * & indices,
const Ogre::Vector3 & position,
const Ogre::Quaternion & orient,
const Ogre::Vector3 & scale)
如此,上帝一一查明了世上的每一个生命,不管这个点式多么的渺小或微不足道,上帝均能一一检视。这里,在每一个面上都计算出了法线向量。
第五天,修改了Node要记得update。
void
Node::needUpdate(
bool
forceParentUpdate)