staticrand.cpp

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/*
 * Copyright (C) Volition, Inc. 1999.  All rights reserved.
 *
 * All source code herein is the property of Volition, Inc. You may not sell 
 * or otherwise commercially exploit the source or things you created based on the 
 * source.
 *
*/ 



#include "math/staticrand.h"
#include "math/vecmat.h"


int Semirand_inited = 0;
int Semirand[SEMIRAND_MAX];

void init_semirand()
{
        int     i;

        Semirand_inited = 1;

        for (i=0; i<SEMIRAND_MAX; i++)
                Semirand[i] = (myrand() << 15) + myrand();
}

int static_rand(int num)
{
        int     a, b, c;

        if (num < 0) 
                num *= -1;

        if (!Semirand_inited)
                init_semirand();

        a = num & (SEMIRAND_MAX - 1);
        b = (num >> SEMIRAND_MAX_LOG) & (SEMIRAND_MAX - 1);
        c = (num >> (2 * SEMIRAND_MAX_LOG)) & (SEMIRAND_MAX - 1);

        return Semirand[a] ^ Semirand[b] ^ Semirand[c];
}

float static_randf(int num)
{
        int     a;

        a = static_rand(num);

        return (a & 0xffff) / 65536.0f;
}

int static_rand_range(int num, int min, int max)
{
        int     rval = static_rand(num);
        rval = (rval % (max - min + 1)) + min;
        CLAMP(rval, min, max);
        return rval;
}

float static_randf_range(int num, float min, float max)
{
        float   rval;
        
        rval = static_randf(num);
        rval = rval * (max - min) + min;

        return rval;
}

void static_randvec(int num, vec3d *vp)
{
        vp->xyz.x = static_randf(num) - 0.5f;
        vp->xyz.y = static_randf(num+1) - 0.5f;
        vp->xyz.z = static_randf(num+2) - 0.5f;

        vm_vec_normalize_quick(vp);
}

void static_rand_cone(int num, vec3d *out, vec3d *in, float max_angle, matrix *orient)
{
        vec3d t1, t2;
        matrix *rot;
        matrix m;

        // get an orientation matrix
        if(orient != NULL){
                rot = orient;
        } else {
                vm_vector_2_matrix(&m, in, NULL, NULL);
                rot = &m;
        }
        
        // axis 1
        vm_rot_point_around_line(&t1, in, fl_radians(static_randf_range(num,-max_angle, max_angle)), &vmd_zero_vector, &rot->vec.fvec);
        
        // axis 2
        vm_rot_point_around_line(&t2, &t1, fl_radians(static_randf_range(num+1,-max_angle, max_angle)), &vmd_zero_vector, &rot->vec.rvec);

        // axis 3
        vm_rot_point_around_line(out, &t2, fl_radians(static_randf_range(num+2,-max_angle, max_angle)), &vmd_zero_vector, &rot->vec.uvec);
}

// Alternate random number generator, that doesn't affect rand() sequence
#define RND_MASK        0x6000
#define RND_MAX 0x7fff
int Rnd_seed = 1;

void init_static_rand_alt(int seed)
{
        Rnd_seed = seed;
}

int static_rand_alt()
{
        static int x=Rnd_seed;
        int old_x;
        old_x = x;
        x >>= 1;
        if ( old_x & 1 ) {
                x ^= RND_MASK;
        }
        return x;
}

float static_randf_alt()
{
        int r = static_rand_alt();
        return i2fl(r)/RND_MAX;
}