Overview
Z-Buffering stores a depth value per pixel and only replaces a pixel when a new fragment is closer.
FoundationSource checked
Z-Buffering
Keeps the closest visible fragment for each pixel.
Quick Facts
Compact metadata for implementation and discovery.
- Category
- Rendering
- Difficulty
- Beginner
- Family
- Visibility
- Tier
- Foundation
- Status
- Verified
- Review
- Source Checked
- Sources
- 1
- Formulas
- 1
- Relationships
- 7
- Code example
- Not ready
- Visualization
- Ready
Core Concepts
per-pixel depthvisibility testdepth comparisonfragment updaterendered imagevisibility orderingvisibilityscene representation
Quick facts
Complexity
Runtime and memory behavior at a glance.
Best
O(f)
Average
O(f)
Worst
O(f)
Space
O(p)
When to Use
- Use it to resolve visible surfaces in a rasterization pipeline.
- Use it when each fragment has a comparable depth value.
- Use it for standard opaque 3D rendering.
When Not to Use
- Avoid relying on it alone for transparent surfaces that need ordering or blending.
- Avoid it when depth precision is insufficient for the near and far plane range.
- Avoid inconsistent depth conventions between projection and comparison.
What It Does
- Tracks depth per pixel
- Rejects hidden fragments
Use Cases
- Real-time 3D rendering
- Visibility testing
- Rasterization pipelines
Inputs
- Fragments with depth values
- Depth buffer
Outputs
- Visible color buffer
- Updated depth buffer
Key Formulas (1)
Depth test
write fragment if depthnew < depthstored
write fragment if depth_new < depth_storedKeeps the closest visible fragment for each pixel.
Pseudocode
- 1.Initialize each pixel depth to far away
- 2.For each fragment:
- 3.Compare fragment depth with stored pixel depth
- 4.Write the color if the fragment is closer
- 5.Update the stored depth
Canonical Example
- Input
- two fragments for one pixel with depths 0.3 and 0.8
- Output
- the color of the depth 0.3 fragment
- Explanation
- With a standard smaller-is-nearer convention, the nearer fragment replaces the farther one.
Implementation Notes
- Initialize the depth buffer to the farthest representable value.
- For each fragment, compare its depth with the stored depth before writing color.
- Keep projection depth mapping and depth-test comparison consistent.
Common Pitfalls
- Setting near and far planes too far apart, which reduces depth precision.
- Using the wrong comparison direction for the depth convention.
- Expecting z-buffering to handle transparency automatically.
Interactive Mechanism Walkthrough
Spatial Primitive & Sweep-Line CanvasShow overlapping fragments competing by depth for the same pixel.
Step 1 of 5: Initialize each pixel depth to far away
depth-bufferNotes
Depth-buffer precision issues often appear as z-fighting between nearly coplanar surfaces.
Sources (1)
What each reference supports for this entry.
Real-Time Rendering
BookComputer graphics reference covering depth buffering and visibility in raster pipelines.
Open sourceExplore Next
Good next jumps from the relationship graph, ranked for useful discovery.
Alternative toShadow Mapping
Rendering · Core
Both compare stored depths, but for different visibility problems.
Compare with thisUsed byRasterization
Rendering · Foundation
Rasterization commonly uses the z-buffer to resolve visibility.
Compare with thisUsed byScanline Rendering
Rendering · Core
Scanline renderers can use depth buffering for visible surface selection.
Compare with thisConceptual neighborsOrder-Independent Transparency
Rendering · Core
Both reason about per-pixel depth, but transparency needs more than one visible layer.
Compare with thisRelationships
View full relationship pageUsed byRasterization
Rasterization commonly uses the z-buffer to resolve visibility.
Alternative toShadow Mapping
Both compare stored depths, but for different visibility problems.
Related Algorithms
Tags
GraphicsVisibilityClassic