因此，我在网上阅读了有关光线追踪的信息，并开始在业余时间从头开始编写光线追踪器。我正在使用 C++，我已经学习了大约一个月了。我已经阅读了网络上的光线追踪理论，到目前为止它工作得很好。它只是一个基本的光线追踪器，既不使用模型也不使用纹理。
起初它制作了一个 Raycaster，并且对结果非常满意。
所以我尝试了多个对象，它也起作用了。我只是在这个实现中使用了漫反射着色，并将光的颜色添加到对象颜色的未着色点。
不幸的是，此代码不适用于多个光源。于是我开始重写我的代码，让它支持多灯。我还阅读了 Phong 照明并开始工作：
它甚至可以与多个灯一起使用：
到目前为止，我很高兴，但现在我有点卡住了。我已经尝试修复这个问题很长一段时间了，但我什么也没想到。当我添加第二个球体甚至第三个球体时，只有最后一个球体被照亮。最后，我的意思是我的数组中存储所有对象的对象。请参见下面的代码。
显然，紫色球体应该有类似的照明，因为它们的中心位于同一平面上。令我惊讶的是，球体只有环境照明 --> 阴影，但情况并非如此。
所以现在我的跟踪功能：
Colour raytrace(const Ray &r, const int &depth)
{
//first find the nearest intersection of a ray with an object
//go through all objects an find the one with the lowest parameter
double t, t_min = INFINITY;
int index_nearObj = -1;//-1 to know if obj found
for(int i = 0; i < objSize; i++)
{
//skip light src
if(!dynamic_cast<Light *>(objects[i]))
{
t = objects[i]->findParam(r);
if(t > 0 && t < t_min) //if there is an intersection and
//its distance is lower than the current min --> new min
{
t_min = t;
index_nearObj = i;
}
}
}
//now that we have the nearest intersection, calc the intersection point
//and the normal at that point
//r.position + t * r.direction
if(t_min < 0 || t_min == INFINITY) //no intersection --> return background Colour
return White;
Vector intersect = r.getOrigin() + r.getDirection()*t;
Vector normal = objects[index_nearObj]->NormalAtIntersect(intersect);
//then calculate light ,shading and colour
Ray shadowRay;
Ray rRefl;//reflected ray
bool shadowed;
double t_light = -1;
Colour finalColour = White;
Colour objectColor = objects[index_nearObj]->getColour();
Colour localColour;
Vector tmpv;
//get material properties
double ka = 0.1; //ambient coefficient
double kd; //diffuse coefficient
double ks; //specular coefficient
Colour ambient = ka * objectColor; //ambient component
//the minimum Colour the obj has, even if object is not hit by light
Colour diffuse, specular;
double brightness;
int index = -1;
localColour = ambient;
//look if the object is in shadow or light
//do this by casting a ray from the obj and
// check if there is an intersection with another obj
for(int i = 0; i < objSize; i++)
{
if(dynamic_cast<Light *>(objects[i])) //if object is a light
{//for each light
shadowed = false;
//create Ray to light
//its origin is the intersection point
//its direction is the position of the light - intersection
tmpv = objects[i]->getPosition() - intersect;
shadowRay = Ray(intersect + (!tmpv) * BIAS, tmpv);
//the ray construcor automatically normalizes its direction
t_light = objects[i]->findParam(shadowRay);
if(t_light < 0) //no imtersect, which is quite impossible
continue;
//then we check if that Ray intersects one object that is not a light
for(int j = 0; j < objSize; j++)
{
if(!dynamic_cast<Light *>(objects[j]))//if obj is not a light
{
//we compute the distance to the object and compare it
//to the light distance, for each light seperately
//if it is smaller we know the light is behind the object
//--> shadowed by this light
t = objects[j]->findParam(shadowRay);
if(t < 0) // no intersection
continue;
if(t < t_light) // intersection that creates shadow
shadowed = true;
else
{
shadowed = false;
index = j;//not using the index now,maybe later
break;
}
}
}
//we know if intersection is shadowed or not
if(!shadowed)// if obj is not shadowed
{
rRefl = objects[index_nearObj]->calcReflectingRay(shadowRay, intersect); //reflected ray from ligh src, for ks
kd = maximum(0.0, (normal|shadowRay.getDirection()));
ks = pow(maximum(0.0, (r.getDirection()|rRefl.getDirection())), objects[index_nearObj]->getMaterial().shininess);
diffuse = kd * objectColor;// * objects[i]->getColour();
specular = ks * objects[i]->getColour();//not sure if obj needs specular colour
brightness = 1 /(1 + t_light * DISTANCE_DEPENDENCY_LIGHT);
localColour += brightness * (diffuse + specular);
}
}
}
//handle reflection
//handle transmission
//combine colours
//localcolour+reflectedcolour*refl_coeff + transmittedcolor*transmission coeff
finalColour = localColour; //+reflcol+ transmcol
return finalColour;
}
接下来是渲染函数：
for(uint32_t y = 0; y < h; y++)
{
for(uint32_t x = 0; x < w; x++)
{
//pixel coordinates for the scene, depends on implementation...here camera on z axis
pixel.X() = ((x+0.5)/w-0.5)*aspectRatio *angle;
pixel.Y() = (0.5 - (y+0.5)/w)*angle;
pixel.Z() = look_at.getZ();//-1, cam at 0,0,0
rTmp = Ray(cam.getOrigin(), pixel - cam.getOrigin());
cTmp = raytrace(rTmp, depth);//depth == 0
pic.setPixel(y, x, cTmp);//writes colour of pixel in picture
}
}
所以这是我的相交函数：
double Sphere::findParam(const Ray &r) const
{
Vector rorig = r.getOrigin();
Vector rdir = r.getDirection();
Vector center = getPosition();
double det, t0 , t1; // det is the determinant of the quadratic equation: B² - 4AC;
double a = (rdir|rdir);
//one could optimize a away cause rdir is a unit vector
double b = ((rorig - center)|rdir)*2;
double c = ((rorig - center)|(rorig - center)) - radius*radius;
det = b*b - 4*c*a;
if(det < 0)
return -1;
t0 = (-b - sqrt(det))/(2*a);
if(det == 0)//one ontersection, no need to compute the second param!, is same
return t0;
t1 = (-b + sqrt(det))/(2*a);
//two intersections, if t0 or t1 is neg, the intersection is behind the origin!
if(t0 < 0 && t1 < 0) return -1;
else if(t0 > 0 && t1 < 0) return t0;
else if(t0 < 0 && t1 > 0) return t1;
if(t0 < t1)
return t0;
return t1;
}
Ray Sphere::calcReflectingRay(const Ray &r, const Vector &intersection)const
{
Vector rdir = r.getDirection();
Vector normal = NormalAtIntersect(intersection);
Vector dir = rdir - 2 * (rdir|normal) * normal;
return Ray(intersection, !dir);
}
//Light intersection(point src)
double Light::findParam(const Ray &r) const
{
double t;
Vector rorig = r.getOrigin();
Vector rdir = r.getDirection();
t = (rorig - getPosition())|~rdir; //~inverts a Vector
//if I dont do this, then both spheres are not illuminated-->ambient
if(t > 0)
return t;
return -1;
}
这是抽象的 Object 类。每个球体、光等都是一个对象。
class Object
{
Colour color;
Vector pos;
//Colour specular;not using right now
Material_t mat;
public:
Object();
Object(const Colour &);
Object(const Colour &, const Vector &);
Object(const Colour &, const Vector &, const Material_t &);
virtual ~Object()=0;
virtual double findParam(const Ray &) const =0;
virtual Ray calcReflectingRay(const Ray &, const Vector &)const=0;
virtual Ray calcRefractingRay(const Ray &, const Vector &)const=0;
virtual Vector NormalAtIntersect(const Vector &)const=0;
Colour getColour()const {return color;}
Colour & colour() {return color;}
Vector getPosition()const {return pos;}
Vector & Position() {return pos;}
Material_t getMaterial()const {return mat;}
Material_t & material() {return mat;}
friend bool operator!=(const Object &obj1, const Object &obj2)
{//compares only references!
if(&obj1 != &obj2)
return true;
return false;
}
};
我使用一个全局对象指针数组来存储世界的所有灯光、球体等：
Object *objects[objSize];
我知道我的代码一团糟，但如果有人知道发生了什么，我将不胜感激。
编辑 1 我添加了图片。
编辑 2 更新了代码，修复了一个小错误。仍然没有解决办法。
更新：添加了渲染代码，用于创建光线。
