Soft Shadow Rendering For 3D Games And Animations

Real-time and interactive rendering is highly emphasized by most of current 3D games with rapid upgrades of modern graphic hardwares.A realistic shadowing effect is also required with large-scale and complex lighting widely adopted in many games and animations.As a consequence, we focus on the real-time realistic soft shadow rendering in the dissertation.At present,some soft shadow rendering algorithm deriving from their hard shadow counterparts,can be only suited to a local lighting rather than the global lighting for a realistic shadowing effect although a realtime render rates can be ensured.On the contrary,such algorithms as ray tracing for global illumination can just be performed in off-line rendering although a true-to-nature result can be achieved.Nevertheless,the PRT approach,which divides the process of the rendering equation computation into two stages with the former undertaking precomputation and the latter rendering shadow in real-time,grantees both the interactive render rates and the realistic render results.Out work is completely based on the PRT framework for dynamic scenes under all frequency lighting environment.Due to the limitation of graphic hardware,visibility can be only sampled on the cubic domain in previous PRT approaches for dynamic scenes.However,object rotation under Haar wavelet basis can hardly be handled on the cubic domain.As a result,we incorporated the spherical polar coordinates in both stages of PRT for sampling and rendering.Thus object rotation can be solved under wavelet basis.To accelerate shadow rendering,we resort to GPU for rendering equation computation.Our main contributions lie in follows:(1)Visibility is sampled in the form of shadow fields to realize shadow rendering in dynamic scenes.We propose an efficient technique for visibility sampling on the spherical polar coordinates by means of the Geometry Shader within the DirectX 10 pipelines.This technique can be extended to other coordinate systems so that PRT approaches for dynamic scenes are no longer confined to the cubic domain.(2)The Tree-structured algorithm is adopted to evaluate the rendering equation.We manage to implement the T-S(short for Tree-Structured) algorithm in the DX10 based GPU execution environment.We propose two solutions against the bottle-neck of register resource,based on which register expense can be minimized.Regarding the speciality of environment lighting,we modify the process of the T-S algorithm to reduce its iterations and optimization has been done accordingly. Furthermore,we optimize the T-S algorithm in all aspects when implementing it on GPU.(3)We put forward a solution for object rotation on the spherical polar coordinates under Haar wavelet basis.Linear transformation is applied to the projection vector of visibility function under Haar wavelet basis through the rotation matrix.Regarding the compact support of highscale Haar wavelet,we optimize the process of both the rotation matrix computation and its wavelet transform.We demonstrate both the efficiency and low error rate of our means for visibility sampling with respect to shadow ray based approaches.Rendering statistic indicate that the shadow rendering is seldom restricted from the bottle neck of register resource and can be sped up significantly based on our realization and optimization for T-S algorithm.Also we demonstrate that shadow results for object rotation can be rendered within very low error rate in real time and rotation matrix can be computed by CPU in real time as well.