tfv: more fixed point conversion

This commit is contained in:
Vince Weaver 2017-08-24 14:40:33 -04:00
parent c84ea111c9
commit 762793f06d

View File

@ -80,17 +80,11 @@ struct fixed_type {
// map coordinates
struct fixed_type speed = {0,0};
// the distance and horizontal scale of the line we are drawing
struct fixed_type distance = {0,0};
struct fixed_type horizontal_scale = {0,0};
// step for points in space between two pixels on a horizontal line
struct fixed_type line_dx = {0,0};
struct fixed_type line_dy = {0,0};
// current space position
struct fixed_type space_x;
struct fixed_type space_y;
// height of the camera above the plane
struct fixed_type space_z= {0x04,0x80}; // 4.5;
@ -112,15 +106,19 @@ static struct fixed_type dy;
static unsigned char speed=SPEED_STOPPED; // 0..4, with 0=stopped
// the distance and horizontal scale of the line we are drawing
static double distance=0;
static double horizontal_scale=0;
static double double_distance=0;
static double double_horizontal_scale=0;
static struct fixed_type distance;
static struct fixed_type horizontal_scale;
// step for points in space between two pixels on a horizontal line
static double line_dx=0;
static double line_dy=0;
// current space position
double space_x,space_y;
static double double_space_x,double_space_y;
static struct fixed_type space_x;
static struct fixed_type space_y;
// height of the camera above the plane
static double space_z=4.5;
@ -130,7 +128,7 @@ static double BETA=-0.5;
static int horizon=-2; // number of pixels line 0 is below the horizon
static double SCALE=20.0;
static double SCALE=16.0;
#define ANGLE_STEPS 16
@ -223,6 +221,32 @@ static void fixed_add(struct fixed_type *x, struct fixed_type *y, struct fixed_t
z->i=x->i+y->i+carry;
}
static void double_to_fixed(double d, struct fixed_type *f) {
int temp;
temp=d*256;
f->i=(temp>>8)&0xff;
f->f=temp&0xff;
}
static void fixed_mul(struct fixed_type *x, struct fixed_type *y, struct fixed_type *z) {
int a,b,c;
a=((x->i)<<8)+(x->f);
b=((y->i)<<8)+(y->f);
c=a*b;
c>>=8;
z->i=(c>>8);
z->f=(c&0xff);
}
//
@ -252,36 +276,50 @@ void draw_background_mode7(void) {
// then calculate the horizontal scale, or the distance between
// space points on this horizontal line
horizontal_scale = space_z / (screen_y + horizon);
double_horizontal_scale = space_z / (screen_y + horizon);
double_to_fixed(double_horizontal_scale,&horizontal_scale);
// calculate the distance of the line we are drawing
distance = horizontal_scale * SCALE;
double_distance = double_horizontal_scale * SCALE;
double_to_fixed(double_distance,&distance);
// printf("Distance=%lf, horizontal-scale=%lf\n",
// distance,horizontal_scale);
// calculate the dx and dy of points in space when we step
// through all points on this line
line_dx = -our_sin(angle) * horizontal_scale;
line_dy = our_cos(angle) * horizontal_scale;
dx.i=fixed_sin[(angle+8)&0xf].i; // -sin()
dx.f=fixed_sin[(angle+8)&0xf].f; // -sin()
fixed_mul(&dx,&horizontal_scale,&dx);
dy.i=fixed_sin[(angle+4)&0xf].i; // cos()
dy.f=fixed_sin[(angle+4)&0xf].f; // cos()
fixed_mul(&dy,&horizontal_scale,&dy);
fixed_to_double(&dx,&line_dx);
fixed_to_double(&dy,&line_dy);
// Move camera back a bit
double factor;
factor=space_z*BETA;
// space_x+=factor*our_cos(angle);
// space_y+=factor*our_sin(angle);
// calculate the starting position
space_x = double_cx + ((distance+factor) * our_cos(angle)) - LOWRES_W/2 * line_dx;
space_y = double_cy + ((distance+factor) * our_sin(angle)) - LOWRES_W/2 * line_dy;
double_space_x = double_cx +
((double_distance+factor) * our_cos(angle)) -
(LOWRES_W/2 * line_dx);
double_space_y = double_cy +
((double_distance+factor) * our_sin(angle)) -
(LOWRES_W/2 * line_dy);
double_to_fixed(double_space_x,&space_x);
double_to_fixed(double_space_y,&space_y);
// go through all points in this screen line
for (screen_x = 0; screen_x < LOWRES_W-1; screen_x++) {
// get a pixel from the tile and put it on the screen
map_color=lookup_map((int)space_x,(int)space_y);
map_color=lookup_map(space_x.i,space_y.i);
ram[COLOR]=map_color;
ram[COLOR]|=map_color<<4;
@ -295,8 +333,8 @@ void draw_background_mode7(void) {
screen_y);
// advance to the next position in space
space_x += line_dx;
space_y += line_dy;
fixed_add(&space_x,&dx,&space_x);
fixed_add(&space_y,&dy,&space_y);
}
}
}