UE4:Shader

UE的材质一般包含了不同的材质模型

基础颜色
Metallic
高光度
粗糙度
各向异性
自发光颜色
不透明度
不透明蒙版
Normal
切线
世界场景位置偏移
世界场景位移
曲面细分乘数
Subsurface Color
Custom Data 0
Custom Data 1
环境光遮挡
折射
像素深度偏移
着色模型

HLSL

UE支持的是HLSL，OpenGL支持的是GLSL

struct Functions
{
        
    float2 csqr( float2 a )  
    { 
        return float2( a.x*a.x - a.y*a.y, 2.*a.x*a.y  ); 
    }

    float2 iSphere( in float3 ro, in float3 rd, in float4 sph )//from iq
    {
        float3 oc = ro;// - sph.xyz;
        float b = dot( oc, rd );
        float c = dot( oc, oc ) - sph.w*sph.w;
        float h = 1.0; //b*b - c;
        return float2(-b-h, -b+h );
    }

    float map(in float3 p, float2 sctime) {
        
        float res = 0.;
        
        float3 c = p;
        c.xy = c.xy * sctime.x + float2(c.y, c.x) * sctime.y;
        for (int i = 0; i < 10; ++i) 
        {
            p =.7*abs(p)/dot(p,p) -.7;
            p.yz= csqr(p.yz);
            p=p.zxy;
            res += exp(-19. * abs(dot(p,c)));        
        }
        return res/2.;
    }

    float3 raymarch( in float3 ro, float3 rd, float2 tminmax , float2 sctime)
    {
        //tminmax += float2(1.,1.) * sin( iTime * 1.3)*3.0;
        float3 one3 = float3(1.,1.,1.);
        float3 t = one3 * tminmax.x;
        
        float3 dt = float3(.07, 0.02, 0.05);
        float3 col= float3(0.0,0.0,0.0);
        float3 c = one3 * 0.;
        for( int i=0; i<64; i++ )
        {
            float3 s = float3(2.0, 3.0, 4.0);   
            t+=dt*exp(-s*c);
            float3 a = step(t,one3*tminmax.y);
            float3 pos = ro+t*rd;
            
            c.x = map(ro+t.x*rd, sctime);
            c.y = map(ro+t.y*rd, sctime);
            c.z = map(ro+t.z*rd, sctime);               
            
            col = lerp(col, .99*col+ .08*c*c*c, a);
        }
        
        // float3 c0 = float3(0.4,0.3,0.99);
        // float3 c1 = float3(0.9,0.7,0.0);
        // float3 c2 = float3(0.9,0.1,0.2);
        return c0 * col.x + c1 * col.y + c2 * col.z;
    }

};

Functions f;
// float time;
// float3 ro;
float2 p = -1.0 + 2.0 * uv;
// p.x *= iResolution.x/iResolution.y;
float2 m = float2(0.0,0.0);

// float3 ro = float3(15.0,0.0,0.0);
float3 ta = float3( 0.0 , 0.0, 0.0 );
float3 ww = normalize( ta - ro );
float3 uu = normalize( cross(ww,float3(0.0,1.0,0.0) ) );
float3 vv = normalize( cross(uu,ww));
float3 rd = normalize( p.x*uu + p.y*vv + 4.0*ww );


float2 tmm = f.iSphere( ro, rd, float4(0.,0.,0.,2.) );

// raymarch
float3 col = f.raymarch(ro,rd,tmm, float2(sin(time), cos(time)));


// shade    
col =  .5 *(log(1.+col));
col = clamp(col,0.,1.);

return float4( col, 1.0 );