Interface GPUTileInternal

Represents a single tile in a tiled coordinate system.

Owned by a GPUTileManager.

Tracks world-space positions, RTC matrices, and usage counts for efficient rendering and memory management. Integrates with GPUTileManager to manage tile-based rendering.

Features:

• Stores world-space center and RTC matrices for multiple views.
• Tracks usage count for efficient memory allocation.
• Supports dynamic movement and reassignment within the tiled system.

Overview

Large-scale 3D scenes require high-precision rendering, which is achieved by partitioning world space into "tiles". Each tile defines a local coordinate system centered at a specific world position, allowing geometry within the tile to be transformed relative to its center (RTC: Relative To Center). This approach minimizes floating-point precision errors when rendering large or distant objects.

Key Components

• GPUTile:

  • Represents a single tile in world space.
  • Stores its center position and per-view RTC matrices (for both camera and picking).
  • Tracks usage count for efficient allocation and reuse.

• GPUTileManager:

  • Allocates, synchronizes, and manages the lifecycle of all tiles.
  • Computes and updates RTC view and pick matrices for each tile as cameras move.
  • Maintains a mapping from world positions to tiles, and manages tile indices for GPU data textures.
  • Uploads updated RTC matrices to MatrixTexture objects for use in shaders.

• MatrixTexture:

  • Stores RTC matrices for all tiles and views in a GPU-friendly format.
  • Updated by the GPUTileManager whenever camera/view state changes.

• DataTextures.viewTileCameraMatrixTexture:

  • An array of MatrixTexture objects, one per view.
  • Each texture contains the RTC view matrices for all tiles in that view.
  • Automatically updated when a camera moves, ensuring the GPU always has the latest RTC transforms.

• DataTextures.viewTilePickMatrixTexture:

  • An array of MatrixTexture objects, one per view.
  • Each texture contains the RTC pick matrices for all tiles in that view, used for accurate object picking.
  • Updated as needed before picking operations.

Matrix Conversion and GPU Upload

• When a tile is created or a camera/view changes, the system computes an RTC view matrix for each tile and view.
• The RTC view matrix is derived by combining the camera's view matrix with a translation that recenters the world origin at the tile's center.
• These RTC matrices are packed into MatrixTexture objects and uploaded to the GPU as data textures.
• Model matrices for objects are also converted to RTC form before upload, ensuring all transformations are relative to the tile center.

Shader Usage

• In the vertex shader, the RTC view and model matrices are fetched from the appropriate MatrixTexture using the tile and view indices.
• Vertex positions are transformed using these RTC matrices, maintaining high precision even for large coordinates.
• This enables accurate rendering and picking across vast scenes without floating-point artifacts.

Workflow Summary

1. Geometry is assigned to a tile based on its world position.
2. The tile's RTC matrices are computed and stored in MatrixTexture objects.
3. When the camera moves, RTC view matrices are updated and re-uploaded to the GPU.
4. Shaders use the RTC matrices to transform geometry, ensuring high-precision rendering and picking.