GPU-Based Responsive Grass

Often large natural environments are essential for todays computer games. Interaction with the environment is widely implemented in order to satisfy the player’s expectations of a living scenery and to help to increase the immersion of the player. Therefore every effort is made towards the implementation of options for interaction with the game-environment. However, in order to achieve a grass simulation as realistic as possible mainly animation and rendering approaches for grass have been researched so far. Within this context my work describes an efficient way to simulate a responsive grass layer with todays graphics cards in real-time. Using the implementation strategie introduced by this diploma thesis clumps of grass are approximated by two billboard representations. Newly introduced stages of the rendering pipeline, first existing on the new graphics hardware, allow the collision handling to take place on the GPU. Distance maps are employed to respond to scene objects. If the analysis of the distance maps indicates a collision of the scene object with one or more gras billboards the deformation of the concerned billboard takes place. In case of collisions and the resulting deformation of the billboards, length constraints preserve the shape of deformed billboards. The recovering process developed throughout this thesis takes place after the deformation caused by colliding with the scene object and restores the original that is to say the undeformed shape for each of the billboards. Additionally, this regeneration process garantees the good overall performance. The primitives of the billboards are assembled during the rendering process. Their vertices are dynamically lit within an ambient occlusion based irradiance volume. Alpha-to-Coverage is used to create the final appearance of the grass layer. Besides the presentation of the theoretical concept that provides the basis of the above-mentioned techniques, the performance concerning the GPU based handling is discussed within the latter part of the examination thesis.