digm520admin / / Math, Mesh, Procedural Generation, Readings, Research, Unity
May 13th, 2018

Procedural Generation

Unite 2016 – The Power of Procedural Meshes

Unity Talk by Alexander Birke

Youtube Link to Talk

Suggested Reading:

“Essential Mathematics for Games – A Programmers Guide” by James M. Van Verth & Lars M. Bishop

Links to examples to learn about procedural generation of meshes
Notes from talk:
    Why use procedural meshes?

  • Player Made Content (Ex. Spore)
  • Unique Mechanics (Ex. Gish)
  • Procedural Generation (Ex. Sir You’re Being Hunted)
Unity Procedural Meshes
  • Mesh starts by creating vertices, and then making triangles from those vertices
  • Components Needed:
    • MeshFilter – stores the mesh
    • MeshRenderer – shows the mesh
    • Script – to generate the mesh
  • Normal vectors used to determine surface orientation
  • Colors
    • Used to be determined by assigning values to vertices
    • Can be used to provide more information to vertices still
    • Can be done as bytes or floats
    • Bytes generally better
  • UVs
    • 2d coordinates for each vertex
    • Used to map textures
    • Create vector2d array to assign to mesh object
  • Setting Trangle Indices
    • Most difficult part
    • Find common features of topology that repeats
    • Draw it out to help find these patterns!
  • Delaunay Triangulation
    • Maximizes angle of all angles of triangles in triangulation
    • Good for GPU rendering since skinny triangles can lead to visual artifacts
    • Port of triangle.net can be found in an above link
  • Debugging Procedural Meshes
    • Very important to do
    • Use Gizmos and Debug classes
    • Rotate camera to check if tris are facing correct direction
    • Turn on wireframe rendering
  • Optimizing Meshes
    • StaticBatchingUtility: batches multiple game objects together into fewer drawcalls but where each can still be culled
    • Mesh.CombineMeshes: Puts many meshes into one, good if individual meshes not likely to cull, but can break things if not done carefully
  • Optimizing Dynamic Meshes
    • Mesh.MarkDynamic: allocates a memory buffer of sorts to designated mesh to let graphics API know mesh data will change often
    • Base data structure to store data in is flat arrays when possible
    • Lists can be used too, especially if you are unsure how many vertices you will need before creating mesh
    • Frustrum Culling
    • Skinned Meshes
  • Multithreaded Mesh Generation: Unity API not thread safe
  • Compute Shaders
    • GPU great for running parallel tasks
    • Only available on modern platforms: PS4, Xbone, DirectX 11, OpenGL 4.3, OpenGL ES 3.1
    • Unity can cross compile with these options
Summary

Procedurally generating a mesh starts with creating vertices, and then triangles from these vertices. Normals and UVs can be added to this data for more informed meshes. In Unity, your mesh will need a MeshFilter and MeshRenderer component. Debugging your mesh is important, and some tools in Unity to help with that are the gizmo and debug classes, moving the camera around, and turning on wireframe rendering. There are also several options to look into to either optimize your existing meshes how they are, or compute them more efficiently.

More to Research
  • Bezier Curves: parametric mathematical curves used commonly in generating computer graphics
  • Use of GPU to do parallel calculations, and how to connect that with Unity scripting
  • Thread and Multithread Mesh Generation: Not sure what this actually meant
  • Computing shaders
  • Talk through Unity by “Sir You’re Being Hunted” on 3D Mesh Generation