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Ray - Sphere intersection test

Started by KriS-XK Mar 11, 2003 at 1:51 PM 4 replies 400+ views

Original Post

Mar 11, 2003 at 1:51 PM

I want to test if a ray intersects a sphere. I found this code in this forum:

  
bool IntersectRaySphere (D3DXVECTOR3& origin, D3DXVECTOR3& dir, D3DXVECTOR3& SphereCenter, float SphereRadius)
{
    D3DXVECTOR3 q;
    D3DXVec3Subtract(&q, &SphereCenter, &origin);
    float c = D3DXVec3Length(&q);
    float v = D3DXVec3Dot(&q, &dir);
    float d = sqrt (SphereRadius) - (sqrt (c) - sqrt (v));
    if (d < 0.0f) 
        return false;

    return true;
}

But it always returns me true value. I''m sure that values are passed to this function corectly as another similar function for testing tri - ray intersection works fine. So where is mistake? Or maybe you could post another code snippet.