Info – Game Programming Terminology – Part 2


**This post follows on from Info – Game Programming Terminology – Part 1.

As per my previous post, the following are terms which you may find useful, again these are inspired by my knowledge and Chad Carters excellent book, XNA Game Studio 3.0 – Unleashed.

Effects:

Effects are quite simply used to get any 3D object to be shown on the screen, with effects like:

  • Textures
  • Light
  • Position of Points

One of the XNA classes to use is BasicEffect which will have one or more technique, and a technique will have one or more passes.

NB: More info to come on the explanation on technique and pass.

Index Buffers:

As we mentioned in the previous post, vertices are stored in Vertex Buffers, which is an area in memory containing lists of vertices. So an index buffer is an area in memory that stores indices that correspond to our Vertex Buffer.

For e.g. if you wanted to draw triangle, you use 3 points (x,y and z if needed) in the vertex buffer, i.e 3 x Vectors (x,y,z). If you want to draw a Rectangle (2 triangles), you could use 6 Vertices in the Vertex Buffer. But because the vertex structs in XNA are memory intensive, AND some of the vertices would be duplicated, then you only need to use 4 in the Vertex Buffer.

The Index Buffer will store 6 indices that correspond to the vertices, in the order we want them rendered. This means only the indices are duplicated and not the complex vertex data.

Good example of this is explained here.

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