static void buildLookAtMatrix(double eyex, double eyey, double eyez,
double centerx, double centery, double centerz,
double upx, double upy, double upz,
ref float[] m)
{
double[] x = new double[3], y = new double[3], z = new double[3];
double mag;
/* Difference eye and center vectors to make Z vector. */
z[0] = eyex - centerx;
z[1] = eyey - centery;
z[2] = eyez - centerz;
/* Normalize Z. */
mag = Math.Sqrt(z[0] * z[0] + z[1] * z[1] + z[2] * z[2]);
if (mag != 0)
{
z[0] /= mag;
z[1] /= mag;
z[2] /= mag;
}
/* Up vector makes Y vector. */
y[0] = upx;
y[1] = upy;
y[2] = upz;
/* X vector = Y cross Z. */
x[0] = y[1] * z[2] - y[2] * z[1];
x[1] = -y[0] * z[2] + y[2] * z[0];
x[2] = y[0] * z[1] - y[1] * z[0];
/* Recompute Y = Z cross X. */
y[0] = z[1] * x[2] - z[2] * x[1];
y[1] = -z[0] * x[2] + z[2] * x[0];
y[2] = z[0] * x[1] - z[1] * x[0];
/* Normalize X. */
mag = Math.Sqrt(x[0] * x[0] + x[1] * x[1] + x[2] * x[2]);
if (mag != 0)
{
x[0] /= mag;
x[1] /= mag;
x[2] /= mag;
}
/* Normalize Y. */
mag = Math.Sqrt(y[0] * y[0] + y[1] * y[1] + y[2] * y[2]);
if (mag != 0)
{
y[0] /= mag;
y[1] /= mag;
y[2] /= mag;
}
/* Build resulting view matrix. */
m[0 * 4 + 0] = (float)x[0]; m[0 * 4 + 1] = (float)x[1];
m[0 * 4 + 2] = (float)x[2]; m[0 * 4 + 3] = (float)(-x[0] * eyex + -x[1] * eyey + -x[2] * eyez);
m[1 * 4 + 0] = (float)y[0]; m[1 * 4 + 1] = (float)y[1];
m[1 * 4 + 2] = (float)y[2]; m[1 * 4 + 3] = (float)(-y[0] * eyex + -y[1] * eyey + -y[2] * eyez);
m[2 * 4 + 0] = (float)z[0]; m[2 * 4 + 1] = (float)z[1];
m[2 * 4 + 2] = (float)z[2]; m[2 * 4 + 3] = (float)(-z[0] * eyex + -z[1] * eyey + -z[2] * eyez);
m[3 * 4 + 0] = (float)0.0; m[3 * 4 + 1] = (float)0.0; m[3 * 4 + 2] = 0.0f; m[3 * 4 + 3] = 1.0f;
}
