src/MirrorShader.h

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#ifndef MIRROR_SHADER_H
#define MIRROR_SHADER_H


#include "Shader.h"
#include "Vec3f.h"
#include "Ray.h"
#include "Scene.h"


class MirrorShader : public Shader
{
public:
    MirrorShader(   Scene *             scene,
                    const RGBAColor &   color)
        : Shader(scene),
            mMirrorColor(color)
    {
    }

    RGBAColor shade(const Ray & ray) const
    {
        assert(ray.hit());
        assert(ray.obj());

        // adaptive recursion termination
        if (ray.influence() < MIN_INFLUENCE || ray.recDeep() > MAX_RECURSION_DEEP)
        {
            // let rays with small influence through the mirror
            Ray newray;
            newray.init(ray.hitPoint(EPSILON), ray.dir());
            newray.updateInfluence(ray);
            return RGBAColor(lerp(mScene->rayTrace(newray).rgb(), mMirrorColor.rgb(), mMirrorColor.a()));
        }

        // get normal of the hit surface
        Vec3f normal = this->normal(ray);

        // compute reflection vector
        Vec3f reflect = ray.dir() - 2*(normal.dot(ray.dir()))*normal;

        // change ray direction and position
        Ray localRay;
        localRay.init(ray.hitPoint(-EPSILON), reflect);
        localRay.updateInfluence(ray, 1.0f - mMirrorColor.a());

        // trace the ray back into the scene
        return RGBAColor(lerp(mScene->rayTrace(localRay).rgb(), mMirrorColor.rgb(),  mMirrorColor.a()));
    }

private:
    RGBAColor mMirrorColor;
};

#endif

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