Multiple subdivision of an icosahedron using HLSL Geometry Shader - directx

Question

Currently I'm subdividing an icosahedron once by using the following Geometry Shader:
[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);
}
However, I want to specify the subdivision level. Is there any possibility to call the Shader again with the outputed verticies or do I need to follow an other approach?

Answer 1

I've solved it in the following way:
[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);
}
}
}