Abstract: A method for determining if an object has been observed by user, said object being rendered in a graphical environment provided to a user with a head-mounted device, where the computer generated graphical environment is able to change over time. The method includes a) determining if the geometric proportion S of the size of the object, in relation to the total field of view generated in the graphical environment, is larger than a predetermined threshold value (Smin), and, if S is larger than Smin, determining for how long time (T) that S is greater than Smin, and if T is greater than a predetermined time Tmin, determining that the object has been observed by the user.

Abstract: A method for determining if an object in a colour three-dimensional environment rendered in real time on a display by a computer is visible for user with a defined point of observation in the three-dimensional environment. The object is defined by at least one area with a predefined colour (CD) where said area is rendered with a colour (CR) that is different from the predefined colour due to the rendering conditions at a defined time point. There is a pre-defined pseudocolour (CP), where a colour is defined as colour values for each of the red (R), green (G) and blue (B) channels.

Abstract: There is provided a method for determining if an object has been observed by user, said object being rendered in a graphical environment provided to a user with a head-mounted device, where the computer generated graphical environment is able to change over time, the method comprising the steps of: a) determining if the geometric proportion S of the size of the object, in relation to the total field of view generated in the graphical environment, is larger than a predetermined threshold value (Smin), and, if S is larger than Smin, determining for how long time (T) that S is greater than Smin, and if T is greater than a predetermined time Tmin, determining that the object has been observed by the user. There is also provided a method for placing objects in a graphical environment.