void computeNormal(float *origin, float *d1, float *d2, float *normal){
float vector1[3], vector2[3];
for(int i =0; i < 3; i++){
vector1[i] = d1[i] - origin[i];
vector2[i] = d2[i] - origin[i];
}
normCrossProd(d1, d2, normal);
}
void findNormal(GLfloat v[3], GLfloat v1[3], GLfloat v2[3], GLfloat out[3]) {
if (v[1] == 0) {
out[0] = 0; out[1] = 1.0; out[2] = 0;
return;
}
GLfloat vect1[3] = {v1[0]-v[0], v1[1]-v[1], v1[2]-v[2]};
GLfloat vect2[3] = {v2[0]-v[0], v2[1]-v[1], v2[2]-v[2]};
normCrossProd(vect1, vect2, out);
}
/* Draw a cylinder with height "h" and "c" segments and "s" size
* The bottom is not drawn because it's not visible
*/
void almostSolidCylinder(float s, int c, float h)
{
GLfloat normal[3];
int i;
float angle, step = 2.0f*M_PI/(float)c;
GLfloat p1[3], p2[3], p3[3], p4[3], v1[3], v2[3];
/* Draw top */
glBegin(GL_POLYGON);
glNormal3f(0.0f, 0.0f, 1.0f);
for (i=0, angle=0.0; i<c; i++, angle+=step)
glVertex3f(cos(angle)*s, sin(angle)*s, 0.0f);
glEnd();
/* Draw stick */
glBegin(GL_QUADS);
for (i=0, angle=0.0; i<c; i++, angle+=step)
{
p1[0] = p2[0] = cos(angle)*s;
p1[1] = p2[1] = sin(angle)*s;
p1[2] = 0.0f;
p2[2] = h;
p3[0] = p4[0] = cos(angle+step)*s;
p3[1] = p4[1] = sin(angle+step)*s;
p3[2] = 0.0f;
p4[2] = h;
/* Do the normal vector */
v1[0] = p1[0] - p3[0];
v1[1] = p1[1] - p3[1];
v1[2] = p1[2] - p3[2];
v2[0] = p2[0] - p3[0];
v2[1] = p2[1] - p3[1];
v2[2] = p2[2] - p3[2];
normCrossProd(v1, v2, normal);
glNormal3fv(normal);
/* Here's the vertexes */
glVertex3f(p2[0], p2[1], p2[2]);
glVertex3f(p4[0], p4[1], p4[2]);
glVertex3f(p3[0], p3[1], p3[2]);
glVertex3f(p1[0], p1[1], p1[2]);
}
glEnd();
}
/* Since GL_QUAD is called prior to this method, it simply list the
corners of the square */
void square(GLfloat va[3], GLfloat vb[3], GLfloat vc[3], GLfloat vd[3])
{
/* The following lines of code are used to create
a normal vector. This is mainly used to ensure
that the object will have a normal for proper
shading */
float v1[3], v2[3], normal[3];
v1[0] = vc[0] - va[0];
v1[1] = vc[1] - va[1];
v1[2] = vc[2] - va[2];
v2[0] = vc[0] - vb[0];
v2[1] = vc[1] - vb[1];
v2[2] = vc[2] - vb[2];
normCrossProd(v1, v2, normal);
glNormal3fv(normal);
glVertex3fv(va);
glVertex3fv(vb);
glVertex3fv(vc);
glVertex3fv(vd);
}
