I had forgotten that there is a pretty good example of collision with gravity and jumping within the example programs in the help file. I'll post it here. run the program, then take a look through the code to try and understand how it was put together:
Rem * Title : Sliding Collision
Rem * Author : DBS-LB
Rem * Date : June 2001
rem ==========================================
rem DARK BASIC EXAMPLE PROGRAM 25
rem ==========================================
rem This program shows use of object sliding
rem collision and simple gravity influences
rem ------------------------------------------
autocam off : sync rate 60
hide mouse : sync on
rem Make four walls
make object box 1,10,200,1000 : position object 1,-500,100,0 : color object 1,rgb(155,40,20)
make object box 2,10,200,1000 : position object 2, 500,100,0 : color object 2,rgb(155,40,20)
make object box 3,1000,200,10 : position object 3, 0,100,-500 : color object 3,rgb(155,40,20)
make object box 4,1000,200,10 : position object 4, 0,100, 500 : color object 4,rgb(155,40,20)
rem Make a floor and create texture for it
make object box 5,1000,10,1000 : position object 5,0,-5,0 : color object 5,rgb(0,255,0)
create bitmap 1,32,32 : cls rgb(0,155,0) : ink rgb(0,145,0),0 : box 4,4,12,12
get image 1,0,0,32,32 : delete bitmap 1 : texture object 5,1
scale object texture 5,200,200
rem Make a pedestal steps
for t=0 to 4
make object box 6+t,50,8,50
position object 6+t,0,4+(t*10),100+(t*50)
color object 6+t,rgb(100,200,100)
next t
rem Make a player object (and a non-rotated collision box for it)
make object cylinder 11,10
position object 11,0,0,0
color object 11,rgb(20,100,255)
make object collision box 11,-5,-5,-5,5,5,5,0
disable object zdepth 11
rem Make the pedastal use non-rotated box collision
for t=0 to 4
make object collision box 6+t,-25,-4,-25,25,4,25,0
next t
rem Make the wall and floor objects into static objects (for auto-camera collision)
for t=1 to 5
make static object t
objx#=object position x(t)
objy#=object position y(t)
objz#=object position z(t)
objsx#=object size x(t)/2.0
objsy#=object size y(t)/2.0
objsz#=object size z(t)/2.0
make static collision box objx#-objsx#,objy#-objsy#,objz#-objsz#,objx#+objsx#,objy#+objsy#,objz#+objsz#
delete object t
next t
rem Make sky black
color backdrop 0
rem Start off player gravity
playergrav#=2.0
rem Main loop
do
rem User prompts
ink rgb(255,255,0),0
center text 320,2,"SHOWS OBJECT SLIDING COLLISION AND CAMERA FOLLOW COMMANDS"
center text 320,20,"USE ARROWS TO MOVE AND SPACE TO JUMP"
rem Store old positions
oldposx#=object position x(11)
oldposy#=object position y(11)
oldposz#=object position z(11)
rem Control player object
if upkey()=1 then move object 11,2
if downkey()=1 then move object 11,-2
if leftkey()=1 then yrotate object 11,wrapvalue(object angle y(11)-3)
if rightkey()=1 then yrotate object 11,wrapvalue(object angle y(11)+3)
if spacekey()=1 and playergrav#=0.0 then playergrav#=2.0
rem Get current object position
posx#=object position x(11)
posy#=object position y(11)
posz#=object position z(11)
rem Handle a touch of gravity
playergrav#=playergrav#-0.1
posy#=posy#+playergrav#
rem Handle sliding collision for player object with other objects
position object 11,posx#,posy#,posz#
if object collision(11,0)>0
dec posx#,get object collision x()
dec posy#,get object collision y()
dec posz#,get object collision z()
playergrav#=0.0
endif
rem Set a size for the player object
s#=object size y(11)/2.0
rem Ensure camera stays out of static collision boxes
if get static collision hit(oldposx#-s#,oldposy#-s#,oldposz#-s#,oldposx#+s#,oldposy#+s#,oldposz#+s#,posx#-s#,posy#-s#,posz#-s#,posx#+s#,posy#+s#,posz#+s#)=1
dec posx#,get static collision x()
dec posy#,get static collision y()
dec posz#,get static collision z()
if get static collision y()<>0.0 then playergrav#=0.0
endif
rem Update with new object position
position object 11,posx#,posy#,posz#
rem Use camera tracker to follow player object
angle#=object angle y(11)
camdist#=25.0 : camhigh#=posy#+10.0 : camfade#=3.5
set camera to follow posx#,posy#,posz#,angle#,camdist#,camhigh#,camfade#,1
rem Tilt camera down a little
xrotate camera 15
rem For fun, slightly move pedastal step
move object 10,0.01
rem Update screen
sync
rem End loop
loop
rem Restore object if ever leave this loop
enable object zdepth 11
Enjoy your day.
