Overview
Shadow volumes use stencil operations while rendering extruded silhouette geometry to count whether a view ray enters a shadowed region.
ExtendedSource checked
Shadow Volumes
Creates extruded volumes from occluders to identify pixels in shadow.
Quick Facts
Compact metadata for implementation and discovery.
- Category
- Rendering
- Difficulty
- Advanced
- Family
- Visibility
- Tier
- Extended
- Status
- Verified
- Review
- Source Checked
- Sources
- 1
- Formulas
- 0
- Relationships
- 3
- Code example
- Ready
- Visualization
- Ready
Core Concepts
silhouette edgestencil bufferextruded volumevisibility test
Quick facts
Complexity
Runtime and memory behavior at a glance.
Best
O(geometry)
Average
O(geometry + pixels)
Worst
O(geometry + pixels)
Space
O(stencil buffer)
When to Use
- Use when real-time graphics needs silhouette edge.
- Use when the input matches the assumptions behind visibility.
When Not to Use
- Avoid when the effect costs more than the visual improvement for the target hardware.
- Avoid when a simpler algorithm gives the required result with less setup.
What It Does
- Creates extruded volumes from occluders to identify pixels in shadow
- Uses silhouette edge and stencil buffer to guide the work.
- Produces rendered image.
Use Cases
- Real-time graphics
- Offline rendering
- Lighting and visibility effects
Inputs
- Scene geometry
- Materials
- Camera and lighting state
Outputs
- Rendered image
- Visibility or shading buffers
Pseudocode
- 1.Prepare the inputs and state needed for Shadow Volumes.
- 2.Apply the silhouette edge step while the stopping condition has not been met.
- 3.Update intermediate state and discard invalid candidates.
- 4.Return rendered image.
Canonical Example
- Input
- Shadow Volumes input with a small representative case
- Output
- Rendered image
- Explanation
- Shadow Volumes applies silhouette edge to produce rendered image.
Implementation Notes
- Keep the data space for positions, normals, and samples explicit in the implementation.
- Keep the silhouette edge step separate enough to test independently.
Common Pitfalls
- Mixing coordinate spaces or sampling domains leads to artifacts that are hard to debug.
- Forgetting to check edge cases can make Shadow Volumes look correct on only ideal inputs.
Interactive Mechanism Walkthrough
Spatial Primitive & Sweep-Line CanvasShow rays, samples, buffers, or shading terms that contribute to the final pixel.
Step 1 of 4: Prepare the inputs and state needed for Shadow Volumes.
rendering-mechanismNotes
Shadow Volumes should be used with the assumptions and tradeoffs of visibility in mind.
Sources (1)
What each reference supports for this entry.
Explore Next
Good next jumps from the relationship graph, ranked for useful discovery.
Relationships
View full relationship pageAlternative toShadow Mapping
Shadow volumes use geometric volumes rather than depth maps.
Conceptual neighborZ-Buffering
Stencil shadow volumes are often used with depth-tested rendering.
Related Algorithms
Tags
GraphicsShadowVisibilityGeometry