刚刚开始写光线跟踪，今天准备实现阴影的效果，但是发现了一些问题。
先上图：

球体自身的阴影叠加在了球体上方，
并且来自其他球体的影子显示也不正确。我想了很久也没发现问题在哪。
还请各位前辈指点一下。

相关代码：

RGBColor Phong::Shade(ShadeRec &sr)
{
    Vector3D wo(-sr.m_ray.d);
    RGBColor L = m_ambientBRDF->rho(sr, wo) * sr.m_world.m_ambient->L(sr);
    int lightsNum = sr.m_world.m_lights.size();

    for (int i = 0; i < lightsNum; ++i)
    {
        Vector3D wi = sr.m_world.m_lights[i]->GetDirection(sr);
        float ndotwi = sr.m_hitPointNormal * wi;

        if(ndotwi > 0.0)
        {
            bool inShadow = false;

            if(sr.m_world.m_lights[i]->castsShadow())
            {
                Ray shadowRay((sr.m_worldHitPoint + kEpsilon), wi);
                inShadow = sr.m_world.m_lights[i]->inShadow(shadowRay, sr);
            }

            if(!inShadow)
            {
                L += (m_diffuseBRDF->fr(sr, wo, wi) + m_specularBRDF->fr(sr, wo, wi))
                    * sr.m_world.m_lights[i]->L(sr) * ndotwi;
            }
        }
    }

    return L;
}

bool PointLight::inShadow(const Ray &shadowray, const ShadeRec &sr)
{
    float ht(sr.m_t);
    float t;
    int ObjectNum = sr.m_world.m_objects.size();
    float d = m_location.distance(shadowray.o);

    for (int i = 0; i < ObjectNum; ++i)
    {
        if(sr.m_world.m_objects[i]->ShadowHit(shadowray, t) && t < d)
        {
            return true;
        }
    }

    return false;
}


bool Sphere::ShadowHit(const Ray &ray, float &tmin) const
{
    const double ep = 0.01;

    double t0, t1;
    Vector3D oc = ray.o - center;
    double a = ray.d * ray.d;
    double b = 2.0 * oc * ray.d;
    double c = oc * oc - radius * radius;
    double disc = b * b - 4.0 * a * c;

    if (disc < 0.0)
    {
        return false;
    }

    double e = sqrt(disc);
    double denom = 2.0 * a;
    
    t0 = (-b - e) / denom;

    if (t0 > ep)
    {
        tmin = t0;
        return true;
    }

    t1 = (-b + e) / denom;

    if (t1 > ep)
    {
        tmin = t1;
        return true;
    }

    return true;
}