Untiy的Camera信息传入Native Render Plugin

官方的Sample只是画了一个屏幕空间的三角形, 怎么改成世界空间的呢? 以D3D11为例:

Native:

struct ConstantBuffer
{
    DirectX::XMMATRIX World;
    DirectX::XMMATRIX View;
    DirectX::XMMATRIX Projection;
} g_CB;
extern "C" void UNITY_INTERFACE_EXPORT UNITY_INTERFACE_API SetCameraMatrix(float vm[], float pm[])
{
    g_CB.View = XMLoadFloat4x4(&DirectX::XMFLOAT4X4(vm));
    g_CB.Projection = XMLoadFloat4x4(&DirectX::XMFLOAT4X4(pm));
}

由于DirectX Math已经是row major的, 所以不用转置了.
Shader:

cbuffer MyCB : register(b0) 
{
    float4x4 worldMatrix;
    float4x4 viewMatrix;
    float4x4 projectionMatrix;
}
void VS (float3 pos : POSITION, float4 color : COLOR, out float4 ocolor : COLOR, out float4 opos : SV_Position) 
{
    opos = mul(float4(pos, 1), worldMatrix);
    opos = mul(opos, viewMatrix);
    opos = mul(opos, projectionMatrix);

    ocolor = color;
}

C#脚本这边有个细节, 就是投影矩阵需要转换一下, 不能直接取相机的:

    [DllImport("RenderingPlugin")]
    private static extern void SetCameraMatrix(float[] viewMatrix, float[] projectionMatrix);
    private static float[] MatrixToArray(Matrix4x4 _matrix)
    {
        float[] result = new float[16];

        for (int _row = 0; _row < 4; _row++)
        {
            for (int _col = 0; _col < 4; _col++)
            {
                result[_col + _row * 4] = _matrix[_row, _col];
            }
        }

        return result;
    }

    private IEnumerator CallPluginAtEndOfFrames()
    {
        while (true) {
            // Wait until all frame rendering is done
            yield return new WaitForEndOfFrame();

            // Set time for the plugin
            SetTimeFromUnity (Time.timeSinceLevelLoad);

            Matrix4x4 projectionMatrix = GL.GetGPUProjectionMatrix(Camera.current.projectionMatrix, false);
            SetCameraMatrix(MatrixToArray(Camera.current.worldToCameraMatrix), MatrixToArray(projectionMatrix));

            // Issue a plugin event with arbitrary integer identifier.
            // The plugin can distinguish between different
            // things it needs to do based on this ID.
            // For our simple plugin, it does not matter which ID we pass here.
            GL.IssuePluginEvent(GetRenderEventFunc(), 1);
        }
    }

Native这边也可以从视力矩阵中还原出相机位置:

        XMMATRIX invViewMatrix = XMMatrixInverse(nullptr, g_CB.View);
        XMVECTOR eyePos = XMMatrixTranspose(invViewMatrix).r[3];

参考资料

http://forum.unity3d.com/threads/native-c-plugin-in-world-space.196512/
https://github.com/obviousjim/ofxUnity/blob/master/UnityProject/Assets/UseRenderingPlugin.cs
http://docs.unity3d.com/ScriptReference/Camera-projectionMatrix.html