1. A computer apparatus for determining within a few seconds an ablated object region for ablating a region of an object of interest, the apparatus comprising: a memory; a computer processor; geometrical representation providing program code, stored in the memory, configured when executed on the computer processor to provide a geometrical representation of the object of interest, of at least one energy influencing element, and of a spatial relationship between the object of interest and the at least one energy influencing element; ablation element setting program code, stored in the memory, having a user interface configured when executed on the computer processor to allow a user to set an orientation and position of an ablation element with respect to the provided geometrical representation; model ablation region storing program code, stored in the memory, configured when executed on the computer processor to store in the memory a set of predetermined model ablation regions, the model ablation regions determined in advance based on energy distribution and a spatial relationship between a model ablation element and at least one model energy influencing element, wherein the model ablation element models a real ablation element and the at least one model energy influencing element models a real energy influencing element, and wherein a model ablation region defines a region that would be ablated if used in an ablation procedure given a respective spatial relationship between the model ablation element and the at least one model energy influencing element; model ablation region retrieving program code, stored in the memory, configured when executed on the computer processor to retrieve from the model ablation region stored in the memory a model ablation region that corresponds to the spatial relationship between the ablation element in the set orientation and in the set position and the at least one energy influencing element as represented by the provided geometrical representation; and ablated object region determining program code, stored in the memory, configured when executed on the computer processor to determine at least one of a) an ablated object region of the object of interest, wherein the ablated object region is located within the retrieved model ablation region and b) a non-ablated object region of the object of interest, wherein the non-ablated object region is located outside the retrieved model ablation region.