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copied!<p>Well it can provide a more compact structure for rendering high poly models. A displacement map can contain as few as 1 byte per pixel. If you tesselate that up for displacement mapping then you are saving a HUGE amount of memory bandwidth on the GPU. </p> <p>Image for a second a simple vertex struct.</p> <pre><code>struct Vert { float x, y, z; float nx, ny, nz; float u, v; }; </code></pre> <p>That struct is 32 bytes in size. So if you imagine that you can quarter the number of vertices (and you ought to be able to do a HELL of a lot more than that) and replace all other vertices with a 1 byte height map then you the amount of memory used works out as follows:</p> <pre><code>100,000 poly object = 3,200,000 bytes using vertex struct alone. 25,000 polys + 100,000 entry height map = 900,000 bytes. </code></pre> <p>ie dispalcement mapping provides you with the same data in 28% of the memory. WIN! :D</p> <p>If you store a normal map and use the w/a component for height then you use up 400000 bytes for the texture and you are now 1,200,000 bytes in size which is STILL 37.5% of the size. PLUS you can now remove 12 bytes for normal storage and you are really down to the same figure of 900,000 bytes.</p> <p>You ought to be able to get SIGNIFICANTLY higher geometry compression rates than that. So, in summary, you get a better looking model for a fraction of the storage data. </p> <p>As an added bonus, using the normal map/height map system you can also easily scale so that less powerful machines simply use the normal data and you still get reasonably good results. </p>

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