Geometry & Overlap Implementation

Geometry & Overlap Implementation

Why Warp and Edge Blending belongs to the same responsible Technical Layer

Summary

In multi-projector systems, geometry correction and edge blending are not independent features. Together, they define how multiple projection devices behave as a single, continuous visual surface. Because geometry alignment and overlap behavior affect the entire canvas, these functions must be resolved at the system level rather than handled independently inside individual projectors. Once system scale increases, per-device correction leads to cumulative error, drift, and inconsistent visual behavior over time.

This is why geometry and overlap are typically implemented as part of a dedicated processing layer that enforces consistent, repeatable behavior across all outputs. By fixing alignment and blending logic at the system level, long-term visual continuity becomes predictable rather than dependent on device state or recalibration.

This page examines how geometry and overlap are implemented in practice within multi-projector systems, focusing on responsibility placement and long-term system behavior.

Who This Page Is For

This page is written for system architects, simulation engineers, and technical decision-makers responsible for multi-projector display systems where geometry accuracy and long-term stability matter, including:

  • Curved and wrap-around projection screens
  • Simulation and training environments
  • Permanent immersive installations and visualization centers

If your responsibility extends beyond first-day alignment to long-term predictable behavior, this page explains where geometry responsibility must live.

The Root Problem: Geometry, Blending and Overlap, are often treated as separated functions, Not a Responsibility

In many projection systems, geometry correction and edge blending are treated as separate setup tasks:

  • Warp is used to make images fit a surface
  • Edge blending is used to hide overlaps

This approach assumes geometry can be continuously corrected.

In practice, it creates fragile systems:

  • Geometry could shift after maintenance or reboot
  • Overlap alignment changes after source swaps
  • Visual continuity depends on repeated recalibration

The issue is rarely accuracy. It is where geometry responsibility is defined.

Geometry as a System-Level Contract

In a stable multi-projector system, geometry must behave as a fixed contract:

  • The mapping between pixels and physical space is defined once
  • All projectors follow the same geometry model
  • Downstream devices do not reinterpret geometry

This contract cannot live only in calibration tools or device menus. It must live in a technical layer.

Definition — Geometry Contract
The geometry contract is the fixed mapping from pixels to physical space across all projectors in a system. It is owned by the Technical Layer, not by individual projectors. Warp defines the geometry; edge blending preserves continuity within that geometry.

Warp (Geometry adjustment) and Edge Blending: Two Sides of the Same Responsibility

Warp and edge blending are often described as separate functions. Architecturally, they are inseparable.

  • Warp defines geometry
  • Edge blending preserves continuity within that geometry

Blending does not define geometry. It assumes geometry has already been defined correctly. Separating the two fragments responsibility and leads to:

  • Alignment drift
  • Overlapping corrections
  • Unpredictable long-term behavior

A technical layer unifies both, so:

  • Geometry is defined once
  • Overlap behavior is fixed
  • The system behaves the same after every restart

Defining Geometry and Overlap in a Technical Layer vs. Projector-Built-In Geometry

A Difference in Responsibility, Not Capability

Some projectors include powerful built-in geometry and warping tools. From a feature perspective, these tools can appear sufficient. The fundamental difference between projector-built-in geometry and using GeoBox as a technical layer is not about performance, but is where responsibility lives.

Projector-Built-In Geometry

When geometry and blending are handled inside individual projectors:

  • Geometry is defined per device
  • Each projector becomes its own geometry authority
  • Geometry may be reinterpreted after firmware updates or resets

As a result:

  • Multi-projector systems behave as loosely coordinated devices
  • Replacing or servicing a projector redefines geometry

This approach can be acceptable for:

  • Smaller scale installations
  • Temporary installation or environments where recalibration is expected

But it scales poorly in complex or permanent systems.

GeoBox as a System-Level Technical Layer for Geometry and Overlap

When geometry and overlap are handled in one technical layer:

  • Geometry is defined once, upstream of all projectors
  • All projectors receive already-prepared images:  precisely cropped, scaled and rotated.
  • Projectors no longer reinterpret or redefine geometry
  • Optical variations are tolerated, not relied upon

In this architecture:

  • The system, not the projector, owns geometry
  • All outputs follow the same spatial contract
  • Replacing a projector does not redefine geometry
  • Behavior remains consistent across reboots and maintenance

Projectors become light engines, not geometry processors.

Why This Matters in Curved and Immersive Systems

On flat screens, small geometry errors may be tolerable. On curved or wrap-around surfaces:

  • Small errors become immediately visible
  • Continuity breaks immersion
  • Manual correction becomes impractical

This is why curved projection systems force geometry responsibility upstream, before images reach projectors.

When Geometry and Overlap Are Pushed Into Content Preparation

In many large display projects, geometry and overlap challenges are not resolved at the display system level, but instead shifted upstream into content preparation. This typically takes the form of content pre-splitting, where segmentation boundaries, overlap regions, and alignment assumptions are embedded directly into the content files. The underlying assumption is that precise content preparation can compensate for physical installation variability.

In practice, this approach introduces structural risk rather than stability. Once geometry and overlap responsibilities are encoded in content, even minor on-site deviations—such as projector position adjustments or surface tolerances—can invalidate the content itself. This increases rework, amplifies synchronization sensitivity, and tightly couples creative assets to a single physical layout.

Rather than solving geometry and overlap, content pre-splitting demonstrates why these responsibilities cannot reside in the content layer. See → Why Content Pre-Splitting Fails in Large Display Systems

Why GeoBox Hardware-Based (FPGA) design Strengthens System Trust

Software-based geometry correction offers flexibility, but introduces variability:

  • OS scheduling
  • GPU driver changes
  • Application state dependency

A hardware-based technical layer provides:

  • A fixed geometry processing pipeline
  • Predictable timing behavior
  • Repeatable spatial accuracy over time

This does not maximize flexibility. It maximizes trust.

Relationship to the Technical Layer Architecture

This page describes how geometry responsibility is implemented in multi-projector systems.

The same architectural principle applies to:

For the core architectural definition, go to  [Technical Layer Overview]


Key Takeaway

Warp and edge blending are not separate features.

They are two aspects of the same responsibility:

Defining and preserving geometry as a stable system contract.

Projector-built-in tools adjust devices individually. A technical layer defines how the entire system behaves. That difference is architectural, and it determines whether a multi-projector system remains reliable over time. For completed overview about multi-projector systems, go to [Multi-Projector Systems].