Computer Graphics

Shadows

Visibility from the light, and the artifacts of every way of caching it.

Colour is the family; a dashed line is the second member of it.

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G cascaded-shadow-maps Cascaded Shadow Maps shadow-mapping Shadow Mapping cascaded-shadow-maps->shadow-mapping one map cannot cover a whole frustum's depth range moment-shadow-maps Moment Shadow Maps variance-shadow-maps Variance Shadow Maps moment-shadow-maps->variance-shadow-maps two moments light-leak between separated occluders percentage-closer-filtering Percentage-Closer Filtering percentage-closer-filtering->shadow-mapping a single depth compare gives hard, aliased edges percentage-closer-soft-shadows Percentage-Closer Soft Shadows percentage-closer-soft-shadows->percentage-closer-filtering kernel width from blocker distance gives contact hardening ray-traced-shadows Ray-Traced Shadows ray-traced-shadows->shadow-mapping no resolution or bias artifacts, but noise instead next-event-estimation Next Event Estimation ray-traced-shadows->next-event-estimation the visibility term of a direct lighting sample rasterization Rasterization shadow-mapping->rasterization the depth image comes from an ordinary raster pass shadow-volumes Shadow Volumes shadow-volumes->shadow-mapping exact silhouettes, but fill-rate bound variance-shadow-maps->percentage-closer-filtering PCF cost grows with filter width; this prefilters

8 nodes

Shadow Volumes

Extrudes silhouette edges away from the light and uses the stencil buffer to count entries and exits. Geometrically exact, with no resolution artifac… · 1977

Shadow Mapping

Renders depth from the light's point of view, then compares each shaded point against it. Image-based, so cost is independent of geometric complexity… · 1978

Percentage-Closer Filtering

Takes several depth comparisons across the shadow map footprint and averages the binary results. Filtering the comparisons rather than the depths is… · 1987

Percentage-Closer Soft Shadows

Searches for blockers first and sizes the PCF kernel by how far away they are, so shadows sharpen near contact and soften with distance. · 2005

Variance Shadow Maps

Stores depth and squared depth so that Chebyshev's inequality bounds the occluded fraction. The map becomes linearly filterable, so it can be blurred… · 2006

Moment Shadow Maps

Keeps four moments of the depth distribution rather than two, which tightens the bound enough to suppress the light leaking that two moments cannot r… · 2015

Cascaded Shadow Maps

Splits the view frustum by depth and gives each slice its own shadow map, so texel density roughly tracks screen-space size instead of being wasted o…

Ray-Traced Shadows

Traces a ray toward the light per shaded point. No resolution, bias or cascade artifacts at all, replaced by sampling noise and a per-pixel tracing c…