# opengl-knowledge-points

**Repository Path**: lidagitee/opengl-knowledge-points

## Basic Information

- **Project Name**: opengl-knowledge-points
- **Description**: No description available
- **Primary Language**: Unknown
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2021-12-21
- **Last Updated**: 2021-12-21

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# Frustum
    参数(T left, T right, T bottom, T top, T nearVal, T farVal);
    如果是全屏就是(0,width,0,height,nearVal,farVal),左下角是屏幕坐标原点;
    默认eye在(0,0,0),往Z负轴看去，不能更改;
    从透视投影矩阵的推导过程理解
    xp = xe * nearVal / -ze;
    nearVal不可以是0;nearVal和farVal必须都是正数;
    xp是投影后的坐标，xe是摄像机坐标系下的坐标，nearVal为0，xp恒为0.推导原理是根据相似三角形
![frustum](./frustum.png)

# perspective
    参数(T fovy, T aspect, T zNear, T zFar)
    eye可以自定义指定;设定target，可以往任意方向看去。