Real-time Soft Shadow Mapping using the DDOC

Soft shadows provide important information to viewers about spatial relationships between objects. Generating accurate soft shadows in real time has been a focus of research in computer graphics. Shadow mapping is a standard way of generating hard shadows in real time and several methods including Smoothies [Chan and Durand 2003] and penumbra maps [Wyman and Hansen 2003] extend the standard shadow map algorithm to handle soft shadows. A major problem with these methods is that they use the hard shadow regions given by the standard shadow map as an approximation of the umbra regions; therefore, they only capture the outer penumbras, resulting in shadows with larger umbrae that appear darker than accurate soft shadows. We propose a real time soft shadow algorithm that extends the standard shadow map algorithm and captures both inner and outer penumbra, leading to more accurate soft shadows.