1. 일반
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struct appdata
{
float4 vertex : POSITION;
float2 uv : TEXCOORD0;
};
struct v2f
{
float4 vertex : SV_POSITION;
float2 uv : TEXCOORD0;
};
float4 Billboard(float4 vertex)
{
float3 camUpVec = normalize( UNITY_MATRIX_V._m10_m11_m12 );
float3 camForwardVec = -normalize( UNITY_MATRIX_V._m20_m21_m22 );
float3 camRightVec = normalize( UNITY_MATRIX_V._m00_m01_m02 );
float4x4 camRotMat = float4x4( camRightVec, 0, camUpVec, 0, camForwardVec, 0, 0, 0, 0, 1 );
vertex = mul( vertex , unity_ObjectToWorld );
vertex = mul( vertex , camRotMat );
vertex = mul( vertex , unity_WorldToObject );
return UnityObjectToClipPos(vertex);
}
v2f vert (appdata v)
{
v2f o;
o.vertex = Billboard(v.vertex);
o.uv = v.uv;
return o;
}
2. GPU 인스턴싱으로 그리는 경우
Graphics.DrawMeshInstancedIndirect()를 통해 그릴 때, 매개변수 마테리얼의 쉐이더-
Quad 메시
- 컴퓨트 버퍼(
_PositionBuffer)를 통해 각 인스턴스의 위치 지정 _Scale변수 또는 컴퓨트 버퍼를 통해 각 인스턴스의 크기 지정
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StructuredBuffer<float3> _PositionBuffer;
float _Scale;
float4 CalculateVertex(float4 vertex, float3 worldPos)
{
float3 camUpVec = normalize( UNITY_MATRIX_V._m10_m11_m12 );
float3 camForwardVec = -normalize( UNITY_MATRIX_V._m20_m21_m22 );
float3 camRightVec = normalize( UNITY_MATRIX_V._m00_m01_m02 );
float4x4 camRotMat = float4x4( camRightVec, 0, camUpVec, 0, camForwardVec, 0, 0, 0, 0, 1 );
vertex = mul(vertex, camRotMat); // Billboard
vertex.xyz *= _Scale; // Scale
vertex.xyz += worldPos; // Instance Position
// World => VP => Clip
return mul(UNITY_MATRIX_VP, vertex);
}
v2f vert (appdata_full v, uint instanceID : SV_InstanceID)
{
v2f o;
o.vertex = CalculateVertex(v.vertex, _PositionBuffer[instanceID]);
o.uv = v.texcoord;
return o;
}