The HUDS

The HUDS (Heads-Up Displays) for Outpost consist of two main components: a scanner and some tactical information, including fuel, velocity, shields, ammo, number of ships left, and score. This is shown in Figure 15.16. It's all rendered in a nice alien green—I love green. The tactical information is simply GDI-rendered text, but the scanner is DirectX-rendered via lines, bitmaps, and pixels.

Take a look at the scanner code:

void Draw_Scanner(void)
{
// this function draws the scanner

int index,sx,sy; // looping and position

// lock back surface
DDraw_Lock_Back_Surface();

// draw all the rocks
for (index=0; index < MAX_ROCKS; index++)
    {
    // draw rock blips
    if (rocks[index].state==ROCK_STATE_ON)
        {
        sx = ((rocks[index].varsI[INDEX_WORLD_X] –
               UNIVERSE_MIN_X) >> 7) +
              (SCREEN_WIDTH/2) –
              ((UNIVERSE_MAX_X - UNIVERSE_MIN_X) >> 8);
        sy = ((rocks[index].varsI[INDEX_WORLD_Y] –
              UNIVERSE_MIN_Y) >> 7) + 32;

        Draw_Pixel(sx,sy,8,back_buffer, back_lpitch);
        }  // end if

    }  // end for index

// draw all the gunships
for (index=0; index < MAX_GUNSHIPS; index++)
    {
    // draw gunship blips
    if (gunships[index].state==GUNSHIP_STATE_ALIVE)
        {
        sx = ((gunships[index].varsI[INDEX_WORLD_X] –
             UNIVERSE_MIN_X) >> 7) +
               (SCREEN_WIDTH/2) - ((UNIVERSE_MAX_X –
               UNIVERSE_MIN_X) >> 8);
        sy = ((gunships[index].varsI[INDEX_WORLD_Y] –
             UNIVERSE_MIN_Y) >> 7) + 32;

        Draw_Pixel(sx,sy,14,back_buffer, back_lpitch);
        Draw_Pixel(sx+1,sy,14,back_buffer, back_lpitch);

        }  // end if

    }  // end for index

// draw all the mines
for (index=0; index < MAX_MINES; index++)
    {
    // draw gunship blips
    if (mines[index].state==MINE_STATE_ALIVE)
        {
        sx = ((mines[index].varsI[INDEX_WORLD_X] –
             UNIVERSE_MIN_X) >> 7) +
               (SCREEN_WIDTH/2) - ((UNIVERSE_MAX_X –
               UNIVERSE_MIN_X) >> 8);
sy = ((mines[index].varsI[INDEX_WORLD_Y] –
              UNIVERSE_MIN_Y) >> 7) + 32;

        Draw_Pixel(sx,sy,12,back_buffer, back_lpitch);
        Draw_Pixel(sx,sy+1,12,back_buffer, back_lpitch);

        }  // end if

    }  // end for index

// unlock the secondary surface
DDraw_Unlock_Back_Surface();

// draw all the stations
for (index=0; index < MAX_STATIONS; index++)
    {
    // draw station blips
    if (stations[index].state==STATION_STATE_ALIVE)
        {
        sx = ((stations[index].varsI[INDEX_WORLD_X] –
             UNIVERSE_MIN_X) >> 7) +
               (SCREEN_WIDTH/2) - ((UNIVERSE_MAX_X –
               UNIVERSE_MIN_X) >> 8);
        sy = ((stations[index].varsI[INDEX_WORLD_Y] –
             UNIVERSE_MIN_Y) >> 7) + 32;
        // test for state
        if (stations[index].anim_state == STATION_SHIELDS_ANIM_ON)
            {
                       stationsmall.curr_frame = 0;
                       stationsmall.x = sx - 3;
                       stationsmall.y = sy - 3;
                       Draw_BOB(&stationsmall,lpddsback);
            }  // end if
        else
            {
                         stationsmall.curr_frame = 1;
                   stationsmall.x = sx - 3;
                        stationsmall.y = sy - 3;
                       Draw_BOB(&stationsmall,lpddsback);
            }  // end if
        }  // end if
    }  // end for index

// unlock the secondary surface
DDraw_Lock_Back_Surface();

// draw player as white blip
sx = ((int(player_x) - UNIVERSE_MIN_X) >> 7) + (SCREEN_WIDTH/2) –
     ((UNIVERSE_MAX_X - UNIVERSE_MIN_X) >> 8);
sy = ((int(player_y) - UNIVERSE_MIN_Y) >> 7) + 32;

int col = rand()%256;

Draw_Pixel(sx,sy,col,back_buffer, back_lpitch);
Draw_Pixel(sx+1,sy,col,back_buffer, back_lpitch);
Draw_Pixel(sx,sy+1,col,back_buffer, back_lpitch);
Draw_Pixel(sx+1,sy+1,col,back_buffer, back_lpitch);

// unlock the secondary surface
DDraw_Unlock_Back_Surface();

// now draw the art around the edges
hud.x          = 320-64;
hud.y          = 32-4;
hud.curr_frame = 0;
Draw_BOB(&hud,lpddsback);

hud.x          = 320+64-16;
hud.y          = 32-4;
hud.curr_frame = 1;
Draw_BOB(&hud,lpddsback);

hud.x          = 320-64;
hud.y          = 32+128-20;
hud.curr_frame = 2;
Draw_BOB(&hud,lpddsback);

hud.x          = 320+64-16;
hud.y          = 32+128-20;
hud.curr_frame = 3;
Draw_BOB(&hud,lpddsback);

}  // end Draw_Scanner

I wanted you to see a typical scanner function because they tend to be a little messy. Basically, a scanner represents the position of various objects in a game, usually scaled and centered. The problem is making a huge space into a small space and drawing image elements that look realistic. Thus, the scanner imagery usually consists of a number of heterogeneous image elements.

Also, when you're viewing a scanner, you want to be able to quickly pick out important data such as where you are, the positions of the enemies, and so on, so color and shape is very important. In the end, I decided to use one or more pixels to represent enemies, single gray pixels to represent asteroids, and actual bitmaps to represent the outposts. The player's ship is represented by a glowing blob.

Finally, the scanner itself is supposed to be some kind of holographic imaging system. I wanted it to look cool, so I drew some nice bitmaps for the corners of it.

As for the workings of the scanner algorithm, take a look at the code. It does nothing more than divide the position of each object by some constant so the results fit into the window of the scanner.