Isometric view: what happened to my math?

Question

I have a math problem in isometric view. I am reading an article: Axonometric Predictions — A Technical Overview . For an isometric projection part, it gives a mathematical formula for converting a 3D point into a two-dimensional point for the x-part, which is the formula:

x' = ( x − z ) cos(30);

But I also check the wiki for isometric view , so I use the rotation matrices that the wiki gives, calculates itself

x' = x*cos(beta) - z*sin(beta)

Beta is determined by the wiki (angle of rotation of the Y axis, and it should be 45). So what about my math? Or is there something I don’t know about isometric projection?

Answer 1

, cos sin , ?

// C/C++ code

#define PI 3.141592654
static const float PI_RADIANS = PI / 180.f;

inline float DegToRad(float a_Degrees)
{
   return (a_Degrees * PI_RADIANS);
}

inline float RadToDeg(float a_Radians)
{
   return (a_Radians / PI_RADIANS);
}