File indexing completed on 2025-08-03 03:49:54

 /*
 * Copyright (c) 2006-2009 Erin Catto http://www.gphysics.com
 *
 * This software is provided 'as-is', without any express or implied
 * warranty.  In no event will the authors be held liable for any damages
 * arising from the use of this software.
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 * 1. The origin of this software must not be misrepresented; you must not
 * claim that you wrote the original software. If you use this software
 * in a product, an acknowledgment in the product documentation would be
 * appreciated but is not required.
 * 2. Altered source versions must be plainly marked as such, and must not be
 * misrepresented as being the original software.
 * 3. This notice may not be removed or altered from any source distribution.
 */
 
 #include <Box2D/Collision/Shapes/b2CircleShape.h>
 #include <new>
 using namespace std;
 
 b2Shape* b2CircleShape::Clone(b2BlockAllocator* allocator) const
 {
     void* mem = allocator->Allocate(sizeof(b2CircleShape));
     b2CircleShape* clone = new (mem) b2CircleShape;
     *clone = *this;
     return clone;
 }
 
 int32 b2CircleShape::GetChildCount() const
 {
     return 1;
 }
 
 bool b2CircleShape::TestPoint(const b2Transform& transform, const b2Vec2& p) const
 {
     b2Vec2 center = transform.position + b2Mul(transform.R, m_p);
     b2Vec2 d = p - center;
     return b2Dot(d, d) <= m_radius * m_radius;
 }
 
 // Collision Detection in Interactive 3D Environments by Gino van den Bergen
 // From Section 3.1.2
 // x = s + a * r
 // norm(x) = radius
 bool b2CircleShape::RayCast(b2RayCastOutput* output, const b2RayCastInput& input,
                             const b2Transform& transform, int32 childIndex) const
 {
     B2_NOT_USED(childIndex);
 
     b2Vec2 position = transform.position + b2Mul(transform.R, m_p);
     b2Vec2 s = input.p1 - position;
     qreal b = b2Dot(s, s) - m_radius * m_radius;
 
     // Solve quadratic equation.
     b2Vec2 r = input.p2 - input.p1;
     qreal c =  b2Dot(s, r);
     qreal rr = b2Dot(r, r);
     qreal sigma = c * c - rr * b;
 
     // Check for negative discriminant and short segment.
     if (sigma < 0.0f || rr < b2_epsilon)
     {
         return false;
     }
 
     // Find the point of intersection of the line with the circle.
     qreal a = -(c + b2Sqrt(sigma));
 
     // Is the intersection point on the segment?
     if (0.0f <= a && a <= input.maxFraction * rr)
     {
         a /= rr;
         output->fraction = a;
         output->normal = s + a * r;
         output->normal.Normalize();
         return true;
     }
 
     return false;
 }
 
 void b2CircleShape::ComputeAABB(b2AABB* aabb, const b2Transform& transform, int32 childIndex) const
 {
     B2_NOT_USED(childIndex);
 
     b2Vec2 p = transform.position + b2Mul(transform.R, m_p);
     aabb->lowerBound.Set(p.x - m_radius, p.y - m_radius);
     aabb->upperBound.Set(p.x + m_radius, p.y + m_radius);
 }
 
 void b2CircleShape::ComputeMass(b2MassData* massData, qreal density) const
 {
     massData->mass = density * b2_pi * m_radius * m_radius;
     massData->center = m_p;
 
     // inertia about the local origin
     massData->I = massData->mass * (0.5f * m_radius * m_radius + b2Dot(m_p, m_p));
 }