View Full Version : glrotatef and my matrix::rotate

12-13-2013, 03:12 AM
hi all,

i want to obtain a mousellok effect.

using fixed opengl function, this can be made doing


using my matrix class, the result is not as above:

mat4 cammtx;

because camera not still holding the y axis

why can i achieve the same glRotate behaviour with my matrix::rotate implementation?

here is my rotate function (input vector is not normalized, i know, but i pass only unit vectors)

void rotate(float* mr,float* m,float angle,float x,float y,float z)
float a=angle*PI_OVER_180;
float m2[16] = {0};

float c=cos(a);
float s=sin(a);

float xx=x*x,

m2[0] = xx+(1.0f-xx)*c;
m2[4] = (1.0f-c)*x*y-s*z;
m2[8] = (1.0f-c)*x*z+s*y;
m2[3] = 0.0f;

m2[1] = (1.0f-c)*y*x+s*z;
m2[5] = yy+(1.0f-yy)*c;
m2[9] = (1.0f-c)*y*z-s*x;
m2[7] = 0.0f;

m2[2] = (1.0f-c)*z*x-s*y;
m2[6] = (1.0f-c)*z*y+s*x;
m2[10] = zz+(1.0f-zz)*c;
m2[11] = 0.0f;

m2[12] = 0;
m2[13] = 0;
m2[14] = 0;
m2[15] = 1.0f;


float* multiply(float* c,float* aa,float* bb)
for(int i = 0; i < 4; i++)
c[i*4] = bb[i*4] * aa[0] + bb[i*4+1] * aa[4] + bb[i*4+2] * aa[8] + bb[i*4+3] * aa[12];
c[i*4+1] = bb[i*4] * aa[1] + bb[i*4+1] * aa[5] + bb[i*4+2] * aa[9] + bb[i*4+3] * aa[13];
c[i*4+2] = bb[i*4] * aa[2] + bb[i*4+1] * aa[6] + bb[i*4+2] * aa[10] + bb[i*4+3] * aa[14];
c[i*4+3] = bb[i*4] * aa[3] + bb[i*4+1] * aa[7] + bb[i*4+2] * aa[11] + bb[i*4+3] * aa[15];
return c;

thank you for your time


12-14-2013, 12:05 AM
hi elemich,
It might not be my business to ask why, but ..
The functions (or something eqvivalent) are present in both glu and glm (Opengl-mathematics) and there is nothing that prevents you from using it.
I'm not in for checking your code. It's not particular GL but appear in a lot of places all related to 3d graphics.
You get your question through, but what is "a mousellok effect".
"because camera not still holding the y axis" .. is not understood either.

Sooner or later you want to solve matrix-equations (find the inverse matrix). By that time you'll know how glm works and have no problem taking advantage of it ..