| 摘要 |
Soft shadows may include areas that are less clear (more blurry) than other regions. For instance, an area of shadow that is closer to the shadow caster may be clearer than a region that is farther from the shadow caster. When generating a soft shadow, the total amount of light reaching each point on the shadow receiving surface is calculated according to a spatially-varying convolution kernel of the occluder's transparency information. Ray-tracing, traditionally used to determine a spatially varying convolution, can be very CPU intensive. Instead of using ray-tracing, data structures, such as MIP-maps and summed-area tables, or separable linear filters may be used to compute the spatially-varying convolution. For example, a two-dimensional convolution may be computed as two spatially-varying, separable, linear convolution filters—one computing a horizontal component and the other a vertical component of the final 2D convolution.
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