学习光线追踪（格式都乱了，郁闷）
射线类的定义：
class Ray
{
public:
Ray() : m_Origin( vector3( 0, 0, 0 ) ), m_Direction( vector3( 0, 0, 0 ) ) {};
Ray( vector3& a_Origin, vector3& a_Dir );
private:
vector3 m_Origin;
vector3 m_Direction;
};
光线追踪算法：
For each pixel
{
Construct ray from camera through pixel
Find first primitive hit by ray
Determine color at intersection point
Draw color
}
求最近交点
// find the nearest intersection
for ( int s = 0; s < m_Scene->GetNrPrimitives(); s++ )
{
Primitive* pr = m_Scene->GetPrimitive( s );
int res;
if (res = pr->Intersect( a_Ray, a_Dist ))
{
prim = pr;
result = res; // 0 = miss, 1 = hit, -1 = hit from inside primitive
}
}
交点的颜色：
// determine color at point of intersection
pi = a_Ray.GetOrigin() + a_Ray.GetDirection() * a_Dist;
// trace lights
for ( int l = 0; l < m_Scene->GetNrPrimitives(); l++ )
{
Primitive* p = m_Scene->GetPrimitive( l );
if (p->IsLight())
{
Primitive* light = p;
// calculate diffuse shading
vector3 L = ((Sphere*)light)->GetCentre() - pi;
NORMALIZE( L );
vector3 N = prim->GetNormal( pi );
if (prim->GetMaterial()->GetDiffuse() > 0)
{
float dot = DOT( N, L );
if (dot > 0)
{
float diff = dot * prim->GetMaterial()->GetDiffuse();
// add diffuse component to ray color
a_Acc += diff * prim->GetMaterial()->GetColor() * light->GetMaterial()->GetColor();
}
}
}
}
计算反射：
// calculate reflection
float refl = prim->GetMaterial()->GetReflection();
if (refl > 0.0f)
{
vector3 N = prim->GetNormal( pi );
vector3 R = a_Ray.GetDirection() - 2.0f * DOT( a_Ray.GetDirection(), N ) * N;
if (a_Depth < TRACEDEPTH)
{
Color rcol( 0, 0, 0 );
float dist;
Raytrace( Ray( pi + R * EPSILON, R ), rcol, a_Depth + 1, a_RIndex, dist );
a_Acc += refl * rcol * prim->GetMaterial()->GetColor();
}
}
Phong光照公式：intensity = diffuse * (L.N) + specular * (V.R)n
vector3 V = a_Ray.GetDirection();
vector3 R = L - 2.0f * DOT( L, N ) * N;
float dot = DOT( V, R );
if (dot > 0)
{
float spec = powf( dot, 20 ) * prim->GetMaterial()->GetSpecular() * shade;
// add specular component to ray color
a_Acc += spec * light->GetMaterial()->GetColor();
}
计算阴影
// handle point light source
float shade = 1.0f;
if (light->GetType() == Primitive::SPHERE)
{
vector3 L = ((Sphere*)light)->GetCentre() - pi;
float tdist = LENGTH( L );
L *= (1.0f / tdist);
Ray r = Ray( pi + L * EPSILON, L );
for ( int s = 0; s < m_Scene->GetNrPrimitives(); s++ )
{
Primitive* pr = m_Scene->GetPrimitive( s );
if ((pr != light) && (pr->Intersect( r, tdist )))
{
shade = 0;
break;
}
}
}
