Kévin Boulanger

Research projects

Here is a summary of the latest research projects I worked on during my PhD thesis.

High-Frequency Shadows for Real-Time Rendering of Trees (2009)

We present a fast and simple method for adding high-frequency shadows into the foliage of trees rendered in real-time. When leaves of a tree project shadows onto other leaves, determining the relationships between cast shadows and the corresponding occluders is a visually difficult task. We present a method based on this assumption to quickly determine shadows cast by leaves onto other leaves. To this end, we simulate the presence of these shadows rather than projecting them exactly. The characteristics of these simulated shadows (movement, parallax, size, softness and color) evolve realistically when the lighting conditions change. Our method is fast and supports soft shadows.

Tree with shadows     Tree with shadows     Tree with shadows

Rendering Trees with Indirect Lighting in Real Time (2007-2008)

High quality lighting is one of the challenges for interactive tree rendering. To this end, we present a lighting model allowing real-time rendering of trees with convincing indirect lighting. Rather than defining an empirical model to mimic lighting of real trees, we work at a lower level by modeling the spatial distribution of leaves and by assigning them probabilistic properties. We focus mainly on precise low-frequency lighting that our eyes are more sensitive to and we add high-frequency details afterwards. The resulting model is efficient and simple to implement on a GPU.

Tree rendering during the day

Tree rendering during the sunset

Rendering Grass Terrains in Real-Time with Dynamic Lighting (2005-2006)

The abundance of grass on the Earth’s surface makes it an important element of rendered natural 3D scenes. Real-time realistic rendering of grass has always been difficult due to the huge number of grass blades. Overcoming this geometric complexity usually requires many coarse approximations to provide interactive frame rates. However, the performance comes at the cost of poor lighting quality and lack of detail of the grass. We present a grass rendering technique that allows better lighting and parallax effect while maintaining real-time performance, even when managing shadows. The creation of arbitrary shaped patches of grass is made possible using our density management. The latter also allows seamless transitions between levels of detail.

Grass rendering

Automatic Tour Into the Picture (2004)

Automatic Tour Into the Picture (ATIP) is an extension of the Tour Into the Picture method by Youichi Horry et al. that allows an approximative but visually convincing 3D walk-through inside a single image by rendering a box textured using the input image data. The original algorithm requires a long and tedious user interaction to determine the box dimensions and the perspective parameters, and imposes several constraints on the input image orientation. Our method provides automatic and fast camera calibration for any view orientation without using a calibration target nor a tripod. Our method reduces the user interaction, hence only a couple of seconds are required between the input image loading and the final walk-through.

Input image for the ATIP algorithm Result of the ATIP algorithm
Result of the ATIP algorithm Result of the ATIP algorithm