fennec/planning/2D_GRAPHICS.md

2D Graphics (gfx2d)

Table of Contents

• Home
• 2D Graphics (gfx2d)
  • Table of Contents
  • Introduction
    • Structures (gfx2d)

Introduction

  This system handles the rendering of 2D meshes and textures.

Links:

• https://en.wikipedia.org/wiki/Quadtree
• https://developer.nvidia.com/gpugems/gpugems3/part-iv-image-effects/chapter-25-rendering-vector-art-gpu

Structures (gfx2d)

For the 2d rendering framework, Materials need to be rendered independently because we have no size constraints for images. This disallows us from using a meta-shader like in the 3d rendering framework.

struct Object
{
    vec2 location, scale; // A matrix would be 36 bytes, this is instead 20 bytes
    float rotation;
}

• BVH

  • Quadtree
    • Leaf Size and Tree Depth should be calculated by the scene, constraints are as follows:
      • Min Object Size
      • Max Object Size
      • Scene Center
      • Scene Edge
    • Insertions and Updates are done on the CPU
    • Nodes
      • Start Index 32-bits
      • Object Count 32-bits
    • Objects
      • Buffer of Object IDs grouped by Octree Node
  • Culling
    • Starting at each Octree Leaf, traverse upwards.
    • Insert Visible Leaf IDs
      • Track using atomic buffer
  • Generate the Command Buffer for Culled Meshes from the Visible Leaf Buffer
    • Count Materials
    • Count Meshes per Material
  • Generate the Culled Object Buffer by copying objects from the Object Buffer
    • Adjust Buffer Size using the counts
    • Insert using another atomic buffer

• Translucent objects will be sorted. We can cheat by using a z-index instead of a z-coordinate. This will allow us to sort objects as they are created. We can still bulk render each z-index, with meshes and objects being grouped by material.