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Scaleing: Why it works.
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Scaling is a major principle for r_speed reduction in any "Rat" style map. This tutorial will attempt to explain why and how to works so you can make the most out of this r_speed reduction method.
A major misconception on CSG breakdown is that the CSG chops new faces at the boarder lines of the textures dimensions, therefore it has been theorized that larger textures equal lower r_speeds, and that scaling decreases r_speeds because it will chop the textures at the new textures dimensions (which were grator then before). This however is NOT true.
The CSG process does NOT care what texture you are using or what its dimensions are, it makes absolutely no difference. What the CSG does care about however is the -subdivide # (BSP stage) parameter and the dimensions of the face. The -subdivide # parameter has a default and maximum value of 240 and should not be changed.
The CSG has two specific ways to break down faces, they are faces with dimensions less or equal to 240 units, and faces with dimensions greater then 240 units, lets focus on the first one:
The first rule is if a face has dimensions of 240 or less it will be broken up into one poly at a scale of 1 to 1. Of course the face will still be subject to regular breakdown (where polys intersect it) but the faces it breaks down into will never exceed the dimensions of 240 by 240. If the original face is greater then these dimensions then this rule will not apply to it, instead rule two will apply.
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| Sample first rule scenario. Only one face is created. |
The second rule is a face has dimensions greater then 240, it will be broken up in blocks of 224 units, instead of 240.
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| Sample second rule scenario. Four faces are created. |
Now here's where scaling comes in, the chop size is basically a multiple of the subdivide size, so if you have a subdivide size of 224 for a face over 240 by 240 units and a scale of 1 the subdivide size will be 1 * 224 units = 224 units. If you have a scale of two and a subdivide size of 224 for a face over 240 by 240 units the subdivide size will be 2 * 224 units = 448 units. Pretty simple stuff. It also works in both X and Y dimensions (depending on the X and Y scale). i.e. if you had a X scale of 1 and a Y scale of 2 the face would be subdivided in the X direction by 224 units and in the Y direction by 448 units.
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| Sample second rule scenario with 2 by 2 scale. Back to one face. |
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