Function trackballPoint

src/backend/opengl/common.cpp:349–363

}

glm::vec3 trackballPoint(const float pX, const float pY,
                         const float pWidth, const float pHeight)
{
    glm::vec3 P = glm::vec3(1.0*pX/pWidth*2 - 1.0, 1.0*pY/pHeight*2 - 1.0, 0);

    P.y = -P.y;
    float OP_squared = P.x * P.x + P.y * P.y;
    if (OP_squared <= 1*1) {
        P.z = sqrt(1*1 - OP_squared);
    } else {
        P.z = 0;
        P = glm::normalize(P);
    }
    return P;
}