We have developed a CG technique that creates real-time animations of spark discharges. The technique proposed in this paper has factors related to the generation of a discharge, such as electric charge distribution and boundary conditions in a virtual space as the input, and generates spark discharge shape patterns based on the electric field defined by the input information. An electric field is expressed by the Laplace equation. Our method efficiently obtains the numerical solution of the equation using the calculation technique of the conjugate gradient method implemented on GPU, and can cope with dynamic changes in input. It also produces discharge patterns in both two and three dimensions. In addition, an efficient pseudo-dimensional expansion technique is proposed in this paper, which uses multiple two-dimensional electric fields to generate three-dimensional discharge patterns.