mirror of https://github.com/dirtbags/tanks.git
51 lines
1.5 KiB
C
51 lines
1.5 KiB
C
#ifndef __BRAD_H__
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#define __BRAD_H__
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/** Binary scaling library
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*
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* There are B8 binary scaled ints. That means the 8 lowest bits are
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* the fractional part. To convert to a float you'd just divide by 256.
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*
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* The trig functions use brads (Binary Radians). There are 128 brads
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* in 2pi radians. One brad is about 1.4 degrees. Using brads makes
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* trig really fast on a binary computer, and reallier faster on a
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* binary computer without an FPU.
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*
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* You must be careful not to overflow your bs_t. For instance, I wrote
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* this library for a game with a 2^9-pixel-wide playfield. That's
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* 2^17 B8, but I also needed to do distance calculations, which
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* requires squaring things. 2^34 is obviously too big to represent in
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* 32 bits.
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*
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* C's type system leaves a lot to be desired when it comes to making
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* sure you're not mixing these things up with normal ints. Be careful!
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*/
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/* Just to make it clear what scale these functions are dealing with */
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typedef struct {
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int v;
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} bs_t;
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typedef int brad_t;
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/* If you change this, you must also change the lookup tables in
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* brad.c. Don't change this. */
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#define BINARY_SCALE 8
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#define BS_DENOMINATOR 1 << BINARY_SCALE
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#define bs_to_int(n) ((n) >> BINARY_SCALE)
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#define bs_of_int(i) ((i) << BINARY_SCALE)
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bs_t bs_cos(brad_t angle);
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bs_t bs_sin(brad_t angle);
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bs_t bs_tan(brad_t angle);
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brad_t bs_acos(bs_t angle);
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brad_t bs_asin(bs_t angle);
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bs_t bs_mul(bs_t a, bs_t b);
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bs_t bs_div(bs_t a, bs_t b);
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bs_t bs_approx_dist(bs_t dx, bs_t dy);
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#endif /* __BRAD_H__ */
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