
Rotation matrices
I'm currently doing a programming project and decided to leave the easiest bit till last. however, im having some trouble with it ;). im sure im missing something simple.
All i want to do is take some inputted points for a triangle, and rotate them. Is the following code correct?
matrix((vertex[count][X]mX), (vertex[count][Y]mY));
the call is that ^
The theory is to minus the triangle midpoint (mX,mY) from the existing entered points (vertex[count][X], vertex[count][Y]). Then rotate by the matrices. Then shift back.
DEG2RAD is just the conversion factor from degrees to radians needed for sin/cos etc
Code:
void matrix(float tempx, float tempy)
{
int count;
float matrix[4]={cos(5*DEG2RAD), sin(5*DEG2RAD), sin(5*DEG2RAD), cos(5*DEG2RAD)};
for(count=0; count<=3; count++)
{
vertex[count][X]=(matrix[0]*tempx)+(matrix[2]*tempx)+mX;
vertex[count][Y]=(matrix[1]*tempy)+(matrix[3]*tempx)+mY;
}
return;
}
Its in opengl but im not allowed to use any preritten functions for the rotation or anything
Code tags added by Hammer

this site explains matrix translation, rotation, and the like.
http://www.geocities.com/SiliconVall.../matrices.html

cool i'll take a look, although i did look at some sites like mathworld but the scope goes a little beyond what i wanted... cheers :)

yep sorry just seen the post about adding code tags, i'll remember that :) :$