Unfortunately, it doesn't have an answer that helped at all, so hopefully this will spark a better discussion. Using C++, the task at hand is to program a classic ray tracer. I am using a Phong shading model, and I am able to illuminate my scenes accurately up until I need to cast shadow rays.
Just for reference, here is a picture of what I have so far without attempting shadows:
Following a traditional ray tracing algorithm where I look for the closest object to my pinhole camera, I call the following function that computes the resulting pixel colour:
glm::vec3 Scene::illuminate(Ray* primary, Surface* object, glm::vec3 hitPt)
{
float red, green, blue;
Material m = object->getMaterial();
float p = m.phongCoef;
glm::vec3 kD = m.diffuse;
glm::vec3 kS = m.specular;
glm::vec3 kA = m.ambient;
float iA = m.ambienceIntensity;
float i = lightSrc.lightIntensity;
glm::vec3 n = object->getSurfaceNormalAt(hitPt); //normalized before return.
glm::vec3 viewRay = primary->getDirection(); //normalized class member.
glm::vec3 lightRay = glm::normalize((lightSrc.getOrigin()) - hitPt); //origin not normalized before here
glm::vec3 h = glm::normalize(viewRay + lightRay);
float nDotlightRay = glm::dot(n,lightRay);
float nDoth = glm::dot(n, h);
bool inShadow = false;
Ray shadowRay;
//hitPt = glm::normalize(hitPt);
shadowRay.setOrigin(hitPt);
shadowRay.setDirectionVector(lightRay);
for (int k = 0; k < objects.size(); ++k) {
if (objects.at(k)->intersect(shadowRay)) {
//std::cout<<shadowRay.getDirection().x<<","<< shadowRay.getDirection().y <<","<<shadowRay.getDirection().z<<"\n";
inShadow = true;
break;}}
//plug in to shading model
if (inShadow)
{
red = kA.x*iA;
green = kA.y*iA ;
blue = kA.z*iA ;
}
else{
red = kA.x*iA + kD.x*i*(fmax(0,nDotlightRay)) + kS.x*i*(powf((fmax(0, nDoth)),p));
green = kA.y*iA + kD.y*i*(fmax(0,nDotlightRay)) + kS.y*i*(powf((fmax(0, nDoth)),p));
blue = kA.z*iA + kD.z*i*(fmax(0,nDotlightRay)) + kS.z*i*(powf((fmax(0, nDoth)),p));
}
glm::vec3 pixelColor = glm::vec3(red, green, blue);
return pixelColor;
}
I have tried to use descriptive variable/function names so as to minimize the explanation that accompanies my code. glm::vec3 is just a data structure from the GLM math library that holds a 3D vector on which matrix/vector manipulations can be done.
As in the question I linked above, here is what my scene looks like after trying shadows.
The light position for this scene is (0, 2.5, -7.75) expressed in the camera reference frame (which has an origin of (0,0,0) and is facing the negative z-direction). For another scene, the light source is at (4, 6, -1) and for that the output isn't even consistent with the problems of the other scene I tried to render as you can see here; it only has a thin grey line across the top of the scene, no shadows anywhere else? I am completely lost and have spent about 10 hours on this problem alone; any advice would be great.
Please let me know if there is any other information else I can provide, such as how I calculate distance and hitPoint?? I dont know if I should look into those since the shading part works perfectly, or do you guys think it Could still cause this problem? Depth and such shouldn't be a problem since the objects look correct up until shadows?
