Unity Shader 序列帧动画

原理：计算每个时刻需要播放的关键帧在纹理中的位置，当播放速度达到一定值时，看起来就是一个连续的动画

Shader "anim"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
		_HorizontalAmount("Horizontal Amount",Float) = 4 //水平方向关键帧图像个数
		_VerticalAmount("Vertical Amount",float) = 4 //垂直方向关键帧图像个数
		_Speed("Speed",Range(1,100)) = 30

    }
    SubShader
    {
        Tags { "RenderType"="Transparent" "Queue" = "Transparent" "IgnoreProjector" = "True" }
        LOD 100

        Pass
        {
			ZWrite Off
			Blend SrcAlpha OneMinusSrcAlpha
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            // make fog work
            #pragma multi_compile_fog

            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                float2 uv : TEXCOORD0;
                UNITY_FOG_COORDS(1)
                float4 vertex : SV_POSITION;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;
			fixed _HorizontalAmount;
			fixed _VerticalAmount;
			fixed _Speed;

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                float time = floor(_Time.y * _Speed);
				float row = floor(time / _HorizontalAmount);
				float column = time - row * _HorizontalAmount;

				half2 uv = i.uv + half2(column, -row);
				uv.x /= _HorizontalAmount;
				uv.y /= _VerticalAmount;

                fixed4 col = tex2D(_MainTex, uv);
				
                return col;
            }
            ENDCG
        }
    }
}

首先把_Time.y和速度属性_Speed相乘得到模拟的时间，然后用floor函数对结果取整得到对应的行索引，除法结果的余数就是列索引.