bool raymarchHit (float3 position, float3 direction)
{for (int i = 0; i < STEPS; i++){if ( sphereHit(position) )return true;position += direction * STEP_SIZE;}return false;
}bool sphereHit (float3 p)
{return distance(p,_Centre) < _Radius;
}

float sphereDistance (float3 p)
{return distance(p,_Centre) - _Radius;
}

fixed4 raymarch (float3 position, float3 direction)
{for (int i = 0; i < STEPS; i++){float distance = sphereDistance(position);if (distance < MIN_DISTANCE)return i / (float) STEPS;position += distance * direction;}return 0;
}

float sdf_smin(float a, float b, float k = 32)
{float res = exp(-k*a) + exp(-k*b);return -log(max(0.0001,res)) / k;
}

float3 normal (float3 p)
{const float eps = 0.01; return normalize( float3 (map(p + float3(eps, 0, 0) ) - map(p - float3(eps, 0, 0)),map(p + float3(0, eps, 0) ) - map(p - float3(0, eps, 0)),map(p + float3(0, 0, eps) ) - map(p - float3(0, 0, eps))) );
}

// Upgrade NOTE: replaced '_Object2World' with 'unity_ObjectToWorld'Shader "Unlit/VolumetricText"
{Properties{_BaseColor ("Base Color", Color) = (1,1,1,1)_SphereColor ("Sphere Color", Color) = (1,0,0,1)_SphereCentre("Sphere Centre",Vector) = (0,0,0)_ShpereRange ("Sphere Range", Range(0.1,2)) = 0.8}SubShader{Tags { "RenderType"="Opaque" "LightMode" = "ForwardBase" }LOD 100Pass{CGPROGRAM#include "Lighting.cginc"#pragma vertex vert#pragma fragment frag#include "UnityCG.cginc"struct appdata{float4 vertex : POSITION;    };struct v2f{float4 vertex : SV_POSITION;float3 wPos : TEXCOORD0; //世界坐标};float4 _BaseColor;float4 _SphereColor;float3 _SphereCentre;fixed _ShpereRange;//有向距离函数float SphereDistance(float3 p){return distance(p, _SphereCentre) - _ShpereRange;}//光线追踪fixed Raymarch(float3 position, float3 direction){float STEPS = 10;float MIN_DISTANCE = 0.01;for (int i = 0; i < STEPS; i++){float distance = SphereDistance(position);if (distance < MIN_DISTANCE)return i / (float)STEPS;position += distance * direction;}return 0;}//法线模拟_简单球形测试float3 NormalEstimation_Sphere(float3 p){return normalize(p - _SphereCentre);}v2f vert (appdata v){v2f o;o.vertex = UnityObjectToClipPos(v.vertex);o.wPos = mul(unity_ObjectToWorld, v.vertex).xyz;return o;}fixed4 frag (v2f i) : SV_Target{fixed4 col = _BaseColor;float3 viewDirection = normalize(i.wPos - _WorldSpaceCameraPos);fixed rayHit = Raymarch(i.wPos, viewDirection);if (rayHit >= 0.01)col = _SphereColor;//丢弃不在形状内的,测试,不在的改为白色clip(col.a - 0.01);fixed3 normal = NormalEstimation_Sphere(i.wPos);//简单处理下光照fixed3 lightDir = _WorldSpaceLightPos0.xyz; // Light directionfixed3 lightCol = _LightColor0.rgb; // Light colorfixed NdotL = max(dot(normal, lightDir), 0);col.rgb = col * lightCol * NdotL;return col;}ENDCG}}
}