Lesson 3 - Adding the Chase Camera

Lesson 3 starts our journey into creating a third person viewer (chase cam) for following our player (a cube) through the game environment. After this lesson you'll start to get the feel for how movement trough a 3D environment works.

                                    ` This code was downloaded from The Game Creators
                                    ` It is reproduced here with full permission
                                    ` http://www.thegamecreators.com
                                    
                                    `---------------------------
`Limit Rush
`Lesson 03
`---------------------------
`http://www.binarymoon.co.uk
`Ben aka Mop
`---------------------------

`--------
`INCLUDES
`--------
`include the MatEdit LoadMatrix files
#include "LoadMatrix.dba"

`------
`ARRAYS
`------
`declare the MatEdit variables
Dim BigMatrix(600,600,1)
Dim StartLoc_X(1): Dim StartLoc_Z(1):Dim Info(2)
Dim TArrayX(1): Dim TArrayZ(1): Dim FKey(10,1)
Dim ColData(100): Dim ZoneData(100): Dim Tiles(500,500)
Dim OverTexture$(100): Dim OverName$(20): Dim ReplaceTex(100)
Dim MOffsetX(25): Dim MOffsetY(25)
Dim MWire(20): Dim MGhost(20): Dim Lock(20)
Dim MatX#(20): Dim MatY#(20): Dim MatZ#(20)
Dim MatWidth#(20): Dim MatHeight#(20)
Dim TilesX(20): Dim TilesZ(20)
Dim MatHi#(20): Dim MatLo#(20)


`----------
`Initialize Variables
`----------
ArenaXYZ_SF = 15000
LightXZ_SF# = .46
LightY_SF# = .55



`set up the program
sync on
sync rate 40
hide mouse
autocam off

`load the matrix
LoadMatrix("map",1)

`temporary load level info
load object "media/arena.x",100
load object "media/arena_light.x",101

`scale the arena
scale object 100, ArenaXYZ_SF, ArenaXYZ_SF, ArenaXYZ_SF
scale object 101, ArenaXYZ_SF*LightXZ_SF#, ArenaXYZ_SF*LightY_SF#, ArenaXYZ_SF*LightXZ_SF#

`position arena
position object 100,247,189,247
position object 101,247,189,247


`add mip-mapping
set matrix texture 1,2,1
set object texture 100,0,1
set object texture 101,2,1

`set fake light properties
set object  101,1,1,0,1,0,0,1
ghost object on 101

`set fog properties
fog on
fog distance 2000
fog color RGB(128,0,0)

`set ambient light amount
set ambient light 10

`colour main light
color light 0,RGB(0,0,160)

`make a light
make light 1
set point light 1,250,200,250
color light 1,RGB(255,255,100)

`make a temporary player object
make object cube 1,5
position object 1,250,1,250


`---------
`MAIN LOOP
`---------
main:
do

   yAng# = object angle y(1)

   `the following is temporary. There will be more but it will made later
   `get keyboard input for movement
   if upkey()=1 then move object 1, 4
   if downkey()=1 then move object 1, -4
   if leftkey()=1 then yrotate object 1, wrapvalue(yAng# - 4)
   if rightkey()=1 then yrotate object 1, wrapvalue(yAng# + 4)

   `sort out the camera height
   xPos#= object position x(1)
   zPos#= object position z(1)
   yPos#= get ground height(1,xPos#,zPos#)

   `update the objexts position
   position object 1, xPos#,yPos#,zPos#

   `update chase camera
   chase_cam(1)


   `display camera object postition
   text 5,5,  "X Position = " + str$(xPos#)
   text 5,25, "Y Position = " + str$(yPos#)
   text 5,45, "Z Position = " + str$(zPos#)

   `update the screen
   sync
loop


`=============
`chase cam
`=============
function chase_cam(id)

   `work out the angle of the object being chased
   yAng#= wrapvalue(object angle y(id)+180)


   `grab the objects current position
   xPos# = object position x(id)
   yPos# = object position y(id)
   zPos# = object position z(id)

   `other variables
   camDist = 15
   camHeight = 5

   `work out new position
   xCamPos# = newxvalue(xPos#,yAng#,camDist)
   zCamPos# = newzvalue(zPos#,yAng#,camDist)

   `work out camera height
   yCamPos# = get ground height (1,xCamPos#,zCamPos#)+camHeight
   if yCamPos# < yPos#+camHeight then yCamPos# = yPos#+camHeight

   `update camera position
   position camera xCamPos#,yCamPos#+camHeight,zCamPos#
   point camera  xPos#, yPos#+camHeight, zPos#



endfunction