/// <summary>
/// Rotates a mat4 by the given angle
/// </summary>
/// <param name="output">{mat4} out the receiving matrix</param>
/// <param name="a">{mat4} a the matrix to rotate</param>
/// <param name="rad">{Number} rad the angle to rotate the matrix by</param>
/// <param name="axis">{vec3} axis the axis to rotate around</param>
/// <returns>{mat4} out</returns>
public static float[] Rotate(float[] output, float[] a, float rad, float[] axis)
{
float x = axis[0]; float y = axis[1]; float z = axis[2];
float len = GameMath.Sqrt(x * x + y * y + z * z);
float s; float c; float t;
float a00; float a01; float a02; float a03;
float a10; float a11; float a12; float a13;
float a20; float a21; float a22; float a23;
float b00; float b01; float b02;
float b10; float b11; float b12;
float b20; float b21; float b22;
if (GlMatrixMathf.Abs(len) < GlMatrixMathf.GLMAT_EPSILON())
{
return(null);
}
len = 1 / len;
x *= len;
y *= len;
z *= len;
s = GameMath.Sin(rad);
c = GameMath.Cos(rad);
t = 1 - c;
a00 = a[0]; a01 = a[1]; a02 = a[2]; a03 = a[3];
a10 = a[4]; a11 = a[5]; a12 = a[6]; a13 = a[7];
a20 = a[8]; a21 = a[9]; a22 = a[10]; a23 = a[11];
// Construct the elements of the rotation matrix
b00 = x * x * t + c; b01 = y * x * t + z * s; b02 = z * x * t - y * s;
b10 = x * y * t - z * s; b11 = y * y * t + c; b12 = z * y * t + x * s;
b20 = x * z * t + y * s; b21 = y * z * t - x * s; b22 = z * z * t + c;
// Perform rotation-specific matrix multiplication
output[0] = a00 * b00 + a10 * b01 + a20 * b02;
output[1] = a01 * b00 + a11 * b01 + a21 * b02;
output[2] = a02 * b00 + a12 * b01 + a22 * b02;
output[3] = a03 * b00 + a13 * b01 + a23 * b02;
output[4] = a00 * b10 + a10 * b11 + a20 * b12;
output[5] = a01 * b10 + a11 * b11 + a21 * b12;
output[6] = a02 * b10 + a12 * b11 + a22 * b12;
output[7] = a03 * b10 + a13 * b11 + a23 * b12;
output[8] = a00 * b20 + a10 * b21 + a20 * b22;
output[9] = a01 * b20 + a11 * b21 + a21 * b22;
output[10] = a02 * b20 + a12 * b21 + a22 * b22;
output[11] = a03 * b20 + a13 * b21 + a23 * b22;
if (a != output)
{
// If the source and destination differ, copy the unchanged last row
output[12] = a[12];
output[13] = a[13];
output[14] = a[14];
output[15] = a[15];
}
return(output);
}
/// <summary>
/// Generates a look-at matrix with the given eye position, focal point, and up axis
/// </summary>
/// <param name="output">{mat4} out mat4 frustum matrix will be written into</param>
/// <param name="eye">{vec3} eye Position of the viewer</param>
/// <param name="center">{vec3} center Point the viewer is looking at</param>
/// <param name="up">{vec3} up vec3 pointing up</param>
/// <returns>{mat4} out</returns>
public static float[] LookAt(float[] output, float[] eye, float[] center, float[] up)
{
float x0; float x1; float x2; float y0; float y1; float y2; float z0; float z1; float z2; float len;
float eyex = eye[0];
float eyey = eye[1];
float eyez = eye[2];
float upx = up[0];
float upy = up[1];
float upz = up[2];
float centerx = center[0];
float centery = center[1];
float centerz = center[2];
if (GlMatrixMathf.Abs(eyex - centerx) < GlMatrixMathf.GLMAT_EPSILON() &&
GlMatrixMathf.Abs(eyey - centery) < GlMatrixMathf.GLMAT_EPSILON() &&
GlMatrixMathf.Abs(eyez - centerz) < GlMatrixMathf.GLMAT_EPSILON())
{
return(Mat4f.Identity(output));
}
z0 = eyex - centerx;
z1 = eyey - centery;
z2 = eyez - centerz;
len = 1 / GameMath.Sqrt(z0 * z0 + z1 * z1 + z2 * z2);
z0 *= len;
z1 *= len;
z2 *= len;
x0 = upy * z2 - upz * z1;
x1 = upz * z0 - upx * z2;
x2 = upx * z1 - upy * z0;
len = GameMath.Sqrt(x0 * x0 + x1 * x1 + x2 * x2);
if (len == 0)
{
x0 = 0;
x1 = 0;
x2 = 0;
}
else
{
len = 1 / len;
x0 *= len;
x1 *= len;
x2 *= len;
}
y0 = z1 * x2 - z2 * x1;
y1 = z2 * x0 - z0 * x2;
y2 = z0 * x1 - z1 * x0;
len = GameMath.Sqrt(y0 * y0 + y1 * y1 + y2 * y2);
if (len == 0)
{
y0 = 0;
y1 = 0;
y2 = 0;
}
else
{
len = 1 / len;
y0 *= len;
y1 *= len;
y2 *= len;
}
output[0] = x0;
output[1] = y0;
output[2] = z0;
output[3] = 0;
output[4] = x1;
output[5] = y1;
output[6] = z1;
output[7] = 0;
output[8] = x2;
output[9] = y2;
output[10] = z2;
output[11] = 0;
output[12] = -(x0 * eyex + x1 * eyey + x2 * eyez);
output[13] = -(y0 * eyex + y1 * eyey + y2 * eyez);
output[14] = -(z0 * eyex + z1 * eyey + z2 * eyez);
output[15] = 1;
return(output);
}