在做这个之前其实是想研究一下在Unity中交互雪的实现，交互雪顾名思义就是可以进行交互的雪，玩家角色从雪上走过时雪被踩凹陷的效果；交互雪的一种实现方案就是将地面看做一个画板，将玩家角色的躯体看做笔刷，将角色经过的路径绘制为一张图片并作为地面雪的高度图传给shader去进行处理，在实现这个之前对如何实现轨迹的绘制比较感兴趣，故而想先以绘画板为切入点，研究研究。
不过既然研究了，就做一个尽量完整的方案，我想要实现的绘画板应包含如下基本功能：
- 1.笔刷大小调节
- 2.线条颜色调节
- 3.可以自定义笔刷形状
- 4.可自定义线条纹理
- 5.绘制的图片可存储至本地
- 6.带橡皮擦功能
- 7.可一键清空画板
- 8.带撤销和重做功能
说干就干，先介绍一下开发环境：
Unity2022.3.30f1 + Rider
用什么版本和IDE无所谓啦哈哈，就是玩！
需要具备一定的unity基础（有一些基本操作就不一一截图了），和shaderlab基础，不需要太深，感兴趣的话可以跟着我一起来做。
技术路线选择
其实要实现绘画的功能有很多种实现方式，例如，可以使用Texture2D.SetPixel, Texture2D.SetPixels，也可以使用Unity提供的图形接口Graphics.DrawTexture，从执行效率上来讲，Graphics.DrawTexture的效率更高一些，Texture2D的相关接口通过遍历像素来实现效率低一些，且不方便实现我们想要的可自定义线条纹理和笔刷形状的功能，因此本文采用Graphics.DrawTexture来实现
源代码：
/// <summary>
/// <para>Draw a texture in screen coordinates.</para>
/// </summary>
/// <param name="screenRect">Rectangle on the screen to use for the texture. In pixel coordinates with (0,0) in the upper-left corner.</param>
/// <param name="texture">Texture to draw.</param>
/// <param name="sourceRect">Region of the texture to use. In normalized coordinates with (0,0) in the bottom-left corner.</param>
/// <param name="leftBorder">Number of pixels from the left that are not affected by scale.</param>
/// <param name="rightBorder">Number of pixels from the right that are not affected by scale.</param>
/// <param name="topBorder">Number of pixels from the top that are not affected by scale.</param>
/// <param name="bottomBorder">Number of pixels from the bottom that are not affected by scale.</param>
/// <param name="color">Color that modulates the output. The neutral value is (0.5, 0.5, 0.5, 0.5). Set as vertex color for the shader.</param>
/// <param name="mat">Custom Material that can be used to draw the texture. If null is passed, a default material with the Internal-GUITexture.shader is used.</param>
/// <param name="pass">If -1 (default), draws all passes in the material. Otherwise, draws given pass only.</param>
[ExcludeFromDocs]
public static void DrawTexture(Rect screenRect, Texture texture, Material mat)
{
Graphics.DrawTexture(screenRect, texture, mat, -1);
}
[ExcludeFromDocs]
public static void DrawTexture(Rect screenRect, Texture texture)
{
Graphics.DrawTexture(screenRect, texture, (Material) null, -1);
}在下面的文章中我们会详细介绍该接口的用法。