使用HLSL幾何着色器

Question

目前我正在使用下面的幾何着色器，一旦細分二十面體的二十面體的多個分區：

[maxvertexcount(8)] 
void gs(triangle VS_OUT gin[3], inout TriangleStream<GS_OUT> s) 
{ 
    //  p1 
    //  /\ 
    // / \ 
    //  m0 --- m1 
    // /\ /\ 
    // / \/ \ 
    // p0 -- m2 -- p2 

    float3 m0 = .5f * (gin[0].pos_l + gin[1].pos_l), 
      m1 = .5f * (gin[2].pos_l + gin[1].pos_l), 
      m2 = .5f * (gin[0].pos_l + gin[2].pos_l); 

    float3 v[6]; 
    v[0] = gin[0].pos_l; 
    v[1] = m0; 
    v[2] = m2; 
    v[3] = m1; 
    v[4] = gin[2].pos_l; 
    v[5] = gin[1].pos_l; 

    GS_OUT gout; 
    for (int i = 0; i < 5; ++i) 
    { 
     gout.pos_h = mul(float4(v[i], 1.f), g_mat_wvp); 
     s.Append(gout); 
    } 
    s.RestartStrip(); 

    gout.pos_h = mul(float4(v[1], 1.f), g_mat_wvp); 
    s.Append(gout); 

    gout.pos_h = mul(float4(v[5], 1.f), g_mat_wvp); 
    s.Append(gout); 

    gout.pos_h = mul(float4(v[3], 1.f), g_mat_wvp); 
    s.Append(gout); 
} 

不過，我想指定的細分級別。是否有可能再次使用輸出的頂點調用Shader，還是需要採用其他方法？

Answer 1

我通過以下方式解決了這個問題：

[maxvertexcount(128)] 
void gs(triangle VS_OUT gin[3], inout TriangleStream<GS_OUT> s) 
{ 
    if (g_subdivs != 0 && g_subdivs <= MAX_SUBDIVISION_LEVEL) 
    { 
     uint level_count = (uint)pow(2, g_subdivs); 
     float3 u = (gin[1].pos_l - gin[0].pos_l)/level_count, 
       w = (gin[2].pos_l - gin[0].pos_l)/level_count, 
       v = gin[0].pos_l; 

     for (int level = level_count; level > 0; --level) 
     {    
      GS_OUT gout; 
      gout.pos_h = mul(float4(normalize(v), 1.f), g_mat_wvp); 
      s.Append(gout); 

      float3 p = v; 
      uint vertex_count = level + 1; 

      for (uint vertex = 1; vertex < vertex_count; ++vertex) 
      { 
       gout.pos_h = mul(float4(normalize(p + u), 1.f), g_mat_wvp); 
       s.Append(gout); 

       gout.pos_h = mul(float4(normalize(p += w), 1.f), g_mat_wvp); 
       s.Append(gout); 
      } 

      v += u; 
      s.RestartStrip(); 
     } 
    } 
    else 
    { 
     [unroll] 
     for (uint i = 0; i < 3; ++i) 
     { 
      GS_OUT gout; 
      gout.diff = gin[i].diff; 
      gout.pos_h = mul(float4(gin[i].pos_l, 1.f), g_mat_wvp); 

      s.Append(gout); 
     } 
    } 
}