void
drawCompassTriangle(float scale)
{
int i;
struct point p, aux;
float size = 3 / scale;
vecMinus(compass[S], compass[P], &aux);
glPolygonMode(GL_FRONT_AND_BACK,GL_LINE);
glPushMatrix();
glBegin(GL_TRIANGLES);
for (i = 0; i < COMPASS_POINT_N; i++) {
if (i == S)
continue;
vecMinus(compass[i], compass[P], &p);
vecTimes(&p, size);
if( i == A || i == D) /* makes the triangle less flattened */
vecPlus(p, aux, &p);
vecPlus(compass[P], p, &p);
glVertex2f(p.x * scale, p.y * scale);
}
glEnd();
glPopMatrix();
glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
}
bool intersectRaySphere(Ray *ray, Sphere *sphere, float *t)
{
bool ret = FALSE;
/* Compute A, B and C coefficients */
//printf("Ray Pos: %d\n", ray->position->x);
//printf("Sphere Pos: %d\n", sphere->position->x);
float a = vecDot(&ray->direction, &ray->direction);
Vector dist = vecMinus(&ray->position, &sphere->position);
float b = 2 * vecDot(&dist, &ray->direction);
float c = vecDot(&dist, &dist) - (sphere->radius * sphere->radius);
/* Find discriminant */
float disc = b * b - 4 * a * c;
/* If discriminant is negative, there are no real roots.
* Return false as the ray misses the sphere. */
if(disc < 0)
return FALSE;
/* Compute q */
float discSqrt = sqrtf(disc);
float q;
if(b < 0)
q = (-b - discSqrt)/2.0;
else
q = (-b + discSqrt)/2.0;
/* The roots */
float t0 = q / a;
float t1 = c / q;
if(t0 > t1)
t0 = t1;
/* Verify t0 larger than 0 and less than the original t */
if((t0 > 0.001f) && (t0 < *t)){
*t = t0;
ret = TRUE;
}
return ret;
}
