// Upgrade NOTE: replaced '_Object2World' with 'unity_ObjectToWorld'

Shader "RayMarch/Primitives0_diffuse"
{Properties{_MainTex ("Texture", 2D) = "white" {}}SubShader{Tags { "RenderType"="Opaque" }LOD 100Pass{CGPROGRAM#pragma vertex vert#pragma fragment frag#include "UnityCG.cginc"#include "Lighting.cginc"struct appdata{float4 vertex : POSITION;float2 uv : TEXCOORD0;};struct v2f{float2 uv : TEXCOORD0;float4 vertex : SV_POSITION;};sampler2D _MainTex;float4 _MainTex_ST;//###################################################################################//sdf:define primitives float sdPlane(float3 p,float planeYPos){return p.y - planeYPos;}float sdSphere(float3 p, float3 spherePos, float radius){return length(p - spherePos) - radius;}//###################################################################################//###################################################################################//primitives boolean operation//求并集
            float2 opU(float2 d1, float2 d2){return (d1.x<d2.x) ? d1 : d2;}    //###################################################################################// define the scenefloat2 map(in float3 pos){//plane//float2(x,y)的第二个参数定义了该物体的材质id，在render环节，可以根据id做不同处理float2 plane = float2(sdPlane(pos, -0.5), 1);float2 ball_1 = float2(sdSphere(pos, float3(0, 0, 2), 0.5), 2);float2 ball_2 = float2(sdSphere(pos, float3(2, 0, 5), 0.5), 2);float2 ball_3 = float2(sdSphere(pos, float3(-2, 0, 5), 0.5), 2);//求物体的并集float2 res = opU(opU(opU(ball_1, ball_2), ball_3),plane);return res;}float2 castRay(in float3 ro, in float3 rd){float tmin = 1.0;//射线最大允许经过的距离float tmax = 100.0;//当前已经过的距离float t = tmin;//材质idfloat m = -1.0;//最大迭代次数定位64for (int i = 0; i<64; i++){//距离精度随距离的增加而减小float precis = 0.0005*t;//获得场景中物体距离该点的距离，及距离最近物体的材质idfloat2 res = map(ro + rd*t);//如果与场景物体发生碰撞，或者射线行进距离超出最大范围，则跳出迭代if (res.x<precis || t>tmax) break;t += res.x;m = res.y;}if (t>tmax) m = -1.0;return float2(t, m);}//计算碰撞点处物体表面的法线float3 calcNormal(in float3 pos){float3 eps = float3(0.0005, 0.0, 0.0);float3 nor = float3(map(pos + eps.xyy).x - map(pos - eps.xyy).x,map(pos + eps.yxy).x - map(pos - eps.yxy).x,map(pos + eps.yyx).x - map(pos - eps.yyx).x);return normalize(nor);}float3 render(in float3 ro, in float3 rd){//投掷射线，获得与所场景物体的碰撞信息float2 res = castRay(ro, rd);float t = res.x;float m = res.y;float3 pos = ro + t*rd;float3 nor = calcNormal(pos);float3 ref = reflect(rd, nor);//漫反射着色fixed3 lightPos = fixed3(0, 3, 0);fixed3 lightDir = normalize(lightPos - pos);float dif = clamp(dot(nor, lightDir),0, 1);float3 col = float3(dif, dif, dif);return float3(clamp(col, 0.0, 1.0));}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{//虚拟摄像机坐标float3 ro = float3(0,0,-1);//投影面某点坐标float3 p = float3(i.uv - float2(0.5, 0.5),0);//投掷射线float3 rd = normalize(p - ro);fixed4 col = fixed4(render(ro, rd).rgb, 1);// gamma校正col.rgb = pow(col.rgb, float3(0.4545, 0.4545, 0.4545));return col;}ENDCG}}
}