我想要一个空间扭曲的shader

以下是一个简单的空间扭曲shader示例，你可以根据自己的需求进行修改和优化：

Shader "Custom/Twist" {
    Properties {
        _MainTex ("Texture", 2D) = "white" {}
        _TwistAmount ("Twist Amount", Range (0.0, 1.0)) = 0.5
        _TwistSpeed ("Twist Speed", Range (0.0, 10.0)) = 2.0
    }
 
    SubShader {
        Tags { "RenderType"="Opaque" }
        LOD 100
 
        Pass {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"
 
            struct appdata {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };
 
            struct v2f {
                float2 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;
            };
 
            sampler2D _MainTex;
            float _TwistAmount;
            float _TwistSpeed;
 
            v2f vert (appdata v) {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = v.uv;
                return o;
            }
 
            float2 Twist (float2 uv, float amount, float speed) {
                float angle = amount * 360 * sin (speed * _Time.y);
                float2 center = float2 (0.5, 0.5);
                float2 dir = uv - center;
                float dist = length (dir);
                float offset = atan2 (dir.y, dir.x) * 180 / 3.14159;
                offset += angle * dist;
                float2 twisted = center + dist * float2 (cos (offset), sin (offset));
                return twisted;
            }
 
            fixed4 frag (v2f i) : SV_Target {
                float2 twisted = Twist (i.uv, _TwistAmount, _TwistSpeed);
                fixed4 col = tex2D (_MainTex, twisted);
                return col;
            }
            ENDCG
        }
    }
    FallBack "Diffuse"
}

这个shader的效果是将贴图进行扭曲，扭曲程度和速度可以通过调整shader属性来控制。具体的实现原理是通过计算每个像素点的偏移量来实现扭曲效果。