what is the best way to add gravity

Blitz3D Forums/Blitz3D Beginners Area/what is the best way to add gravity

Rubiks14

(Posted 2004) [#1]

yes i know i have been posting alot but i'm just starting and i can't figure out some of these things but anyway what is the best way for gravity u could give me an example or if there is a tutorial i don't know about that will work too, woops wrong forum

wizzlefish

(Posted 2005) [#2]

simple gravity:

TranslateEntity camera, 0, -1, 0

Ross C

(Posted 2005) [#3]

Have a variable called gravity. when the player isn't touching the ground, decrease this variable by 0.1 everyloop, untill he is touching. Make sure the variable doesn't go below -70 though.

gravity# = 0


while not keyhit(1)

   if player not touching ground then; pseudo code
      gravity = gravity - 0.1
      if gravity <-70 then
         gravity = -70
      end if
   else
      gravity = 0
   end if

   moveentity camera,0,sin(gravity),0

Wend

Some rough code. Basically use Sin to create simple acceleration using the sin wave. :o) Works pretty well.

W	(Posted 2005) [#4]

Im having troubles getting it to work, how are you testing to see if your player has collided with the level??

Rob Farley

(Posted 2005) [#5]

This is somethign that I wrote ages ago as a tutorial that might help

; Thrust type example by Rob Farley (http://www.mentalillusion.co.uk)
; Use the cursor keys to move it block around the screen

Graphics 640,480,16 ; set graphics mode
SetBuffer BackBuffer() ; set back buffer to enable screen flipping
Cls


; set up some varibles all of the ones below have a #
; this means they are floating point numbers ie they have a decimal place
x#=320 ;x position
y#=200 ;y position
xspeed#=0 ; xspeed
yspeed#=0 ; yspeed

; these are the keys for control Const sets them up as constant varibles
; this means they can't be changed but it makes everything a bit faster
Const k_left=203, k_right=205, k_up=200 , k_down=208


; start the main loop
Repeat ; note the loop is indented for easy to read code


	Cls ;clear the screen

	Color 0,255,0
	Line 0,470,639,470 ;draw a green line at the bottom of the screen

	If KeyDown(k_left) Then xspeed#=xspeed#-.1 ;this adds acceleration in the correct direction
	If KeyDown(k_right) Then xspeed#=xspeed#+.1
	If KeyDown(k_up) Then yspeed#=yspeed#-.2

	x#=x#+xspeed# ;this adds the acceleration to the current x,y position
	y#=y#+yspeed#

	xspeed#=xspeed#*.99 ;this makes the xspeed 99% of what is was ie adds friction and slows you down
	yspeed#=yspeed#+.05 ; here we are adding gravity acceleration to the y direction so you're always being pulled down


	If y#>460 Then y#=460:yspeed#=-yspeed#/2 ; this is hitting the bottom of the screen and bouncing you up at half the speed you hit it
	If y#<0 Then y#=0:yspeed#=0 ; stopping you at the top of the screen
	If x#>650 Then x#=-10 ; wrapping you from right to left
	If x#<-10 Then x#=650 ; wrapping you from left to right

	Color 255,255,0
	Rect x#-10,y#-10,20,20 ; draw a yellow rectangle at your position

	Flip ; flip the back buffer to the front so you can see what's been drawn

Until KeyHit(1) ; back to the beginning of the main loop until ESC is hit

End ; End the program

octothorpe

(Posted 2005) [#6]

Gravity causes accelleration. To properly model accelleration, you need to keep track of the velocity of your entities. To keep track of additional information for an entity, use a TYPE:

Const GRAVITY# = 0.02

Type physical_body
	Field entity        ; each physical_body represents one entity
	Field vx#, vy#, vz# ; keep track of velocity
End Type

; here's a simple constructor to make it easier to create objects
Function create_physical_body.physical_body(entity)
	this.physical_body = New physical_body
	this\entity = entity
	Return this
End Function

; don't work with entities directly:
;player = createcube()
;positionentity(player, 1, 2, 3)

; instead, create objects to store the entities:
player.physical_body = create_physical_body( CreateCube() )
PositionEntity(player\entity, 1, 2, 3)

; game loop
While Not(KeyHit(1))
	; update all physical_bodies
	For pb.physical_body = Each physical_body
		pb\vy = pb\vy + GRAVITY                    ; add gravity
		TranslateEntity(pb\entity, pb\vx, pb\vy, pb\vz) ; move entity
	Next
	; update graphics
	RenderWorld
	Flip
Wend

Don't call TranslateEntity() directly anymore. Instead, modify the velocity of your physical_bodies and let the physics updating code in the loop move the entity for you.

P.S. Yes, there is a way to find the physical_body object that represents an entity, given only the entity (e.g. from a Pick.) To do so, store the object's Handle() in the entity's EntityName.

jfk EO-11110

(Posted 2005) [#7]

A sidenote: you maybe need to add a pivot right between the feet of the characater to check if he collided with the ground. Checking for ground contact with the entire mesh or the shoes is not a good idea since it/they can touch walls as well, so you would allow him to climb up walls as if he was standing on the ground. Using a pivot between the feet, with an EntityRadius that is big enough to detect the ground and ONLY the ground can fix this.

An other solution is to use a linepick against the ground.

Polarix

(Posted 2016) [#8]

also

Zethrax

(Posted 2016) [#9]

'also' what? If you're making a point or asking a question then you might want to do it less idiotically.

Blitzplotter

(Posted 2016) [#10]

Hmmm, maybe Skydude's spamtastic.