1. Method for computing an exposure pattern for exposing a desired pattern on a target in a charged-particle multi-beam processing apparatus, in which a particle beam is directed to and illuminates a pattern definition device comprising an aperture array composed of a plurality of blanking apertures through which said particle beam penetrates for writing said desired pattern by exposing a multitude of pixels within an image area on the target, wherein in the pattern definition device said plurality of blanking apertures is arranged in a predetermined arrangement defining mutual positions of the blanking apertures, each blanking aperture being selectively adjustable with regard to a dose value to be exposed through the respective blanking aperture onto a corresponding aperture image generated on the target during a respective exposure interval, said dose value taking a respective value selected from a discrete gray scale, wherein during a writing process of said desired pattern, a sequence of exposure intervals is made, wherein in each exposure interval the blanking apertures are imaged onto the target, thus generating a corresponding plurality of aperture images, wherein the method comprises: i) providing the desired pattern as a graphical representation on the image area on the target, said graphical representation having a predetermined width of resolution, said width being larger than a nominal distance between neighboring positions of the pixels within said image area, ii) providing a convolution kernel, said kernel describing a mapping from an element of the graphical representation to a group of pixels, said group of pixels being centered around a nominal position of said element, iii) calculating a nominal exposure pattern as a pixel raster graphics defined on the multitude of pixels, by convolution of the graphical representation with the convolution kernel, said nominal exposure pattern being suitable to create a nominal dose distribution on the target.