private static float _GetZDist(Color c, float FN, float F, float NsF)
{
float bufVal = RTUtil.DecodeFloatRGBA(c);
float zdist = FN / (F + bufVal * NsF);
return(zdist);
}
/// <summary>
/// given the depth-buffer texture and a screen-pos, return the sampled z-dist
/// F: camera farClipPlane
/// N: camera nearClipPlane
/// FN : F*N
/// NsF: N-F
/// </summary>
public static float GetZDistFromDepthBuffer(Texture2D zbuffer, Vector2 screenPos, float FN, float F, float NsF)
{
float norX = screenPos.x / zbuffer.width;
float norY = screenPos.y / zbuffer.height;
Color zBufColor = zbuffer.GetPixel(Mathf.RoundToInt(norX * Screen.width), Mathf.RoundToInt(norY * Screen.height));
float zBufVal = RTUtil.DecodeFloatRGBA(zBufColor);
float zBufDist = FN / (F + zBufVal * NsF);//IMPORTANT!!! z-depth is linearized based on reciprocal
// ------------------------------
// refer: https://en.wikipedia.org/wiki/Bilinear_filtering
// DEPRECATED: not useful, the 4 points all far from right
//float u = norX * Screen.width - 0.5f;
//float v = norY * Screen.height - 0.5f;
//int _x = Mathf.FloorToInt(u);
//int x0 = Mathf.Max(0, _x);
//int x1 = Mathf.Min(_x + 1, Screen.width - 1);
//int _y = Mathf.FloorToInt(v);
//int y0 = Mathf.Max(0, _y);
//int y1 = Mathf.Min(_y + 1, Screen.height - 1);
//float u_ratio = u - _x;
//float v_ratio = v - _y;
//float u_opposite = 1 - u_ratio;
//float v_opposite = 1 - v_ratio;
//float v00 = _GetZDist(zbuffer.GetPixel(x0, y0), FN, F, NsF);
//float v01 = _GetZDist(zbuffer.GetPixel(x0, y1), FN, F, NsF);
//float v10 = _GetZDist(zbuffer.GetPixel(x1, y0), FN, F, NsF);
//float v11 = _GetZDist(zbuffer.GetPixel(x1, y1), FN, F, NsF);
//Dbg.Log("v00: {0}, v01: {1}, v10: {2}, v11: {3}", v00, v01, v10, v11);
//float zBufDist = (v00 * u_opposite + v10 * u_ratio) * v_opposite +
// (v01 * u_opposite + v11 * u_ratio) * v_ratio;
//------------------------------------------
return(zBufDist);
}