Real-Time Terrain with Geo-Mipmapping

This terrain rendering engine with Geo-Mipmapping is one of my research project. Terrain is an outdoor area, which means not much occlusion-based culling can be done to reduce the total amount of polygon being rendered.


To workaround this issue, we need a method to perfrom terrain rendering with CLOD. The concept of CLOD (Continuous Level of Detail) is not too difficult to understand, basically more details are preserved in the areas closer to the camera view than the farther ones. The key is to maintain real-time rendering performance while not sacrificing too much graphic quality.


Algorithms such as ROAM (Real-time Optimal Adapting Mesh) and Chunked Terrain were developed to compute the CLOD at run-time. I chose to implement the Geo-Mipmapping method utilizes the GPU to do the computational load instead of mainly relying on the CPU.


Essentially the whole terrain area is splitted into many smaller terrain blocks. Each block stores a vertex buffer and multiple levels of index buffers, which represent the terrain block at different resotluion. These computations are done at load-time, and during run-time, based on value of pixel-error / distance factor, a suitable LOD is selected to render the terrain block.



One of the major issue with this approach is the gap formed when blocks of different LODs are adjacent, because the shared edges are represented by different numbers of vertices belonging to each block. To seal these gaps, the index buffer of the higher LOD block is re-computed at run-time to reduce the resolution to match that of the lower LOD block, thus effectively sealing up the gaps.

The end result is the capabilty to render an area made of 2M triangles at full resolution with roughly 20k triangles made of various LOD blocks.

Highlights:

• OpenGL API.
• Geo-Mipmapped Terrain.
• Vertex and Index Buffer.
• Gap-filling between terrain blocks.

Game Engine Development

Several techniques I implemented during my 3D engine development class:

• Terrain Following: With several vector cross product computations, the dune buggy can be positioned and oriented to follow the terrain realistically.


• Maya Export Plug-in: By using the Maya Plug-in SDK, I wrote several plug-ins for Maya which can be used to export model and custom attributes into both XML and binary format.


• Collision Detect: AABB, Sphere, and K-DOP collision detecting techniques.


• Camera Views: Mouse-look, Look-At, Turn-to, Hard-attach, Soft-attach camera views with matrix computation.


• Hierarchy Transformation: Establish and compute 3D object heirarchy to reposition parts from their local space to world space.
  

Real-Time 3D Animation Technology

• I've learned and implement several different kinds of real-time 3D animation techniques. Here is the gist of it:
  Vertex Morphing - Stores key frames and use interpolation to animate the vertexes. Memory intensive but light on the CPU.
• Articulated - Individual animated parts are modeled as individual meshes, and bones and joints are used to animate the meshes. Less memory needed, but the joints are blocky because the joints don't share vertexes.
• Skinning (Rigid) - Similar to articulated, but each vertex is associated instead of at per-mesh level. Needs minimal memory, but requires more CPU power. The major draw back is that deformities can happen at the joints when animating.


• Skinning (Smooth) - A vertex can be associated with multiple bones with different weight values, this reduces the deformities at the joints but at the cost of more CPU computations.

OpenGL Rendering

This is my project written with C++ and OpenGL. The goal of this project is to create a real-time 3D playground scene. 3D models are exported into source code and loaded into vertex buffer. The river is an animated mesh which is able to reflect the bridge above, and pointsprite was used to render the grass on the playground.

Highlights:

• OpenGL API
• Vertex animation
• Reflection with Stencil Buffer
• Pointsprite Grass