- "Low-pass filtering statistics", 

- Eigen library (http://eigen.tuxfamily.org) 

Eigen's Geometry module provides two different kinds of geometric transformations:

1. Abstract transformations, such as rotations (represented by angle and axis or by a quaternion), translations, scalings. These transformations are NOT represented as matrices, but you can nevertheless mix them with matrices and vectors in expressions, and convert them to matrices if you wish. 这种类型描述的都是Pure R/T/S. 

2. Projective or affine transformation matrices 两种: see the Transform class. These are really matrices. 其实是Represents an homogeneous transformation in a N dimensional space. 

例如这是一个affine transformation matrix的例子, 描述的是concatenation_of_any_transformations: Transform<float,3,Affine> t = Translation3f(p) * AngleAxisf(a,axis) * Scaling3f(s); 

An affine transformation matrix M is shaped like this:

( linear   translation )

(  0...0       1       ) // the last row can be assumed to be [0...0 1]

Note that for a projective transformation the last row can be anything, and then the interpretation of different parts might be sightly different.

Isometry if the transformation is only a concatenations of translations and rotations. (In Euclidean geometry, a rotation is an example of an isometry, a transformation that moves points without changing the distances between them. from wikipedia)

Transformation Types:

2D rotation from angle                    Rotation2D

3D rotation as an angle + normalized axis AngleAxis

"Finally Rotation2D and AngleAxis are mainly convenient types to create other rotation objects." These are two most simplest rotation types.

- 遇到一个bug. QA用的版本可以稳定重新，但是我就是不能重现，所以我怀疑daily build是不是包含了最新的code. 后来试了最近的check in也包含在daily build里面, 应该就不是没有包含最新code了。同事建议看看release 和 debug版本。果然release version可以重新 debug版本不可以重新. 一直跟踪发现原因一个数组值没有初始化, 在debug中被初始化为3452816845 也就是0xcdcdcdcd, 但在release下大部分是0. 

- NVIDIA path render, 

- 工作需要了解求Normal Map细节，于是读了NVIDIA mesh tool(http://code.google.com/p/nvidia-mesh-tools/)中NVMeshMender的实现, 知道了Tangent space的求法, 例如先根据uv求出TB然后假如N的时候考虑smoothgroup.  NVIDIA的工具Melody虽然没有给出代码实现, 但可以玩玩normal map的生成. 

- "State of the Art Report, Survey of Real-Time Tessellation & Geometry Synthesis Methods" 罗列了相关papers.

- http://www.lysator.liu.se/c/c-faq/c-1.html C-FAQ.

- Check the QScopedPointer for resource acquisition is initialization(RAII), and QSharedPointer for reference count.