// Draw mirror polygon into stencil buffer

glEnable(GL_STENCIL_TEST);
glClear(GL_STENCIL_BUFFER_BIT);
glStencilFunc(GL_ALWAYS, 1, 1);
glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
glBegin(GL_POLYGON);
    for (unsigned int j = 0; j < mirrors[i]->vertexCount(); ++j)
        glVertex3f(mirrors[i]->vertex(j).x(), mirrors[i]->vertex(j).y(), mirrors[i]->vertex(j).z());
glEnd();

// Clear depth buffer

glClear(GL_DEPTH_BUFFER_BIT);

// Reflect position and direction in mirror plane

Plane3d mirrorPlane(mirrors[i]->plane());
const Vec3 originalPosition = Camera::instance().position();
const Vec3 originalDirection = Camera::instance().direction();
const Vec3 mirroredPosition = originalPosition - 2.0f * mirrorPlane.n() *
    mirrorPlane.distance(originalPosition);
Vec3 lookAt = originalPosition + originalDirection;
const Vec3 mirroredDirection = lookAt - 2.0f * mirrorPlane.n() *
    mirrorPlane.distance(lookAt) - mirroredPosition;

// Save new viewpoint/position

Camera::instance().position() = mirroredPosition;
Camera::instance().direction() = mirroredDirection;

glMatrixMode(GL_MODELVIEW);
glPushMatrix();

    // Update worldview matrix to mirrored viewpoint

    Camera::instance().setMatrix();

    // Create mirror clip plane

    const double clipPlane [] = { mirrors[i]->plane().n().x(),
                                    mirrors[i]->plane().n().y(),
                                    mirrors[i]->plane().n().z(),
                                    mirrors[i]->plane().d() };
    glEnable(GL_CLIP_PLANE0);
    glClipPlane(GL_CLIP_PLANE0, clipPlane);

    // Setup stencil to only draw pixels where stencil is set to 1

    glStencilFunc(GL_EQUAL, 1, 1);
    glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);

    // Draw scene (from mirrors viewpoint)

    drawScene(mirroredPosition, mirroredDirection, mirrors[i]->sector(), frustrum_);

    // Disable mirror clip plane and stencil testing

    glDisable(GL_CLIP_PLANE0);
    glDisable(GL_STENCIL_TEST);

    Camera::instance().position() = originalPosition;
    Camera::instance().direction() = originalDirection;

glPopMatrix();