1.原理
通过模型坐标判断,离中心越近越高，否则越低。

2.shader代码

Shader "Custom/Terrian"
{
    properties{
        _Radius("Radius",range(0,5)) = 1.0
    }
    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;
                fixed4 vcol : COLOR;
            };

            float _Radius;

            v2f vert (appdata v)
            {
                v2f o;
                float dis = length(v.vertex.xz);
                dis = _Radius - dis;
                dis = dis < 0 ? 0 : dis;
                float upY = clamp(dis * 0.5,0,5);
                float4 uppos = float4(v.vertex.x,v.vertex.y + upY,v.vertex.z,v.vertex.w);
                o.vertex = UnityObjectToClipPos(uppos);
                o.uv = v.uv;
                o.vcol = fixed4(0,1,0,1) + fixed4(uppos.y,uppos.y,uppos.y,0);
                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                return i.vcol;
            }
            ENDCG
        }
    }
}

3.效果

4.设置中心

Shader "Custom/Terrian"
{
    properties{
        _Radius("Radius",range(0,5)) = 1.0
        _Center("Center",Vector) = (0,0,0,0)
    }
    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;
                fixed4 vcol : COLOR;
            };

            float _Radius;
            float4 _Center;

            v2f vert (appdata v)
            {
                v2f o;
                float dis = length(v.vertex.xz - _Center.xy);
                dis = _Radius - dis;
                dis = dis < 0 ? 0 : dis;
                float upY = clamp(dis * 0.5,0,5);
                float4 uppos = float4(v.vertex.x,v.vertex.y + upY,v.vertex.z,v.vertex.w);
                o.vertex = UnityObjectToClipPos(uppos);
                o.uv = v.uv;
                o.vcol = fixed4(0,1,0,1) + fixed4(uppos.y,uppos.y,uppos.y,0);
                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                return i.vcol;
            }
            ENDCG
        }
    }
}

效果: