directx - Where does WorldViewProj get definenition in hlsl -

as tile,i in fxcomposer play shader code this

float4x4 worldviewproj : worldviewprojection;  struct c2e1v_output{     float position :position;     float color :   color; }   float4 mainvs(float3 pos : position) : position{     return mul(float4(pos.xyz, 1.0), worldviewproj); }   float4 mainps() : color {     return float4(1.0, 1.0, 1.0, 1.0); }  technique technique0 {     pass p0 {         cullmode = none;         vertexshader = compile vs_3_0 mainvs();         pixelshader = compile ps_3_0 mainps();     } } 

but dont know how var "worldviewproj " define,seems there's no code give vlue.can me,thanks.