a simple Vector question (velocity to rotation)

[AnniXa]

Hi =)

I have the following scenario:

A simple invisible tbody that is flying like bullet throught the world, and now i wanted to attach a bullet or missile mesh to this body, and i wanted to calculate the rotation for the missile depending on the velocity vector of the body thingy, and then apply this rotation to the missile mesh and set it on the position of the body, so that it looks like the missile is flying like the body.

 

But for any reason i cant find out how to calculate the rotation that i need for the missile, since the school is long time ago

maybe someone knows a simple way to do oit? maybe there is some prebuild function with the vec3 ojects or something else like this that i missed, or maybe someone knows a simple formula or something for this?

[flachdrache]

You most likely dont need to calculate that since Le is all "entity-based" ...

you simply want to set the position / rotation of your bolt / bullet to the position / rotation of the body or set its complete EntityMatrix.

 

I took "all" the commands i would need to build game-subsystems from the command list and wrote samples for it.

It doesnt help much with integration the game-engine itself but game-mechanics can be extracted from it.

 

here is some, slightly changed, script metraton posted (dont know how to write that name though)

 

--stuff which should be part of LE

--the best working round function, works also for negative idp (written by Robert Jay Gould)
function round(num, idp)
       return tonumber(string.format("%." .. (idp or 0) .. "f", num))
end

BLEND_NONE=0
BLEND_ALPHA=1

--end of stuff which should be part of LE

local width=1920
local height=1080

require("Scripts/constants/collision_const")
require("Scripts/constants/engine_const")
require("Scripts/LinkedList")
require("Scripts/filesystem")
require("Scripts/math/math")
require("scripts/classes/bullet")

if fw==nil then --we are not in Editor
       RegisterAbstractPath("")
       Graphics(800,600)
       fw=CreateFramework()
       scene=LoadScene("abstract::Actors_obstacleDM1.sbx")
       scene:SetCollisionType(COLLISION_SCENE)

       TFilter()        
       AFilter()

       SetHDR(true)
       SetSSAO(true)
       SetBloom(true)  

       standalone=1
end

--Variables
dx=0.0
dy=0.0
camerapitch=0.0
camerayaw=0.0
move=0.0
strafe=0.0
cameraheight=1.9

--ScrennshotBuffers
local buffer=CreateBuffer(width,height,BUFFER_COLOR)
if buffer==nil then
Notify("Failed to create buffer!",1)
return
end

local buffer2=CreateBuffer(width,height,BUFFER_COLOR)
if buffer2==nil then
Notify("Failed to create buffer!",1)
buffer=nil
return
end

--array of "info_playerstart" ... classname
--lobby might use different spots.
local playerstart = nil
playerstart = scene:FindChild("playerstart") 

--Create a player controller
controller=CreateController(1.8, 0.46, 0.25, 45)
controller:SetCollisionType(COLLISION_CHARACTER,0)
controller:SetMass(10)

SweptCollision(controller, 1)

if standalone==1 then
if playerstart ~= nil then
	controller:SetPosition( playerstart:GetPosition() )
else
	controller:SetPosition(Vec3(0,20,0))
end
else
       controller:SetPosition(fw.main.camera.position)
end
camerapitch=fw.main.camera.rotation.x
camerayaw=fw.main.camera.rotation.y+180

controller:Move(Vec3(0,-0.9,0))

local gunscale=0.6
local vwep = LoadMesh("abstract::vwep_hands.gmf")
LoadMesh("abstract::vwep_gun.gmf",vwep)
vwep:SetParent(fw.main.camera,0)
vwep:SetPosition(Vec3(-0.18*gunscale,-0.03*gunscale,0.37*gunscale),0)
vwep:SetScale(Vec3(0.04*gunscale,0.04*gunscale,0.04*gunscale))
local gundisplayposition = vwep:GetPosition()
sound_gunshot = LoadSound("abstract::gunshot.ogg")
source_gunshot = CreateSource(sound_gunshot)
source_gunshot:SetVolume(0.5)
vwep :SetShadowMode(0,1)
local displayposition=Vec3(-0.26/2.0,-0.03,0.19)
local muzzleflash = CreatePointLight(3)
muzzleflash:SetParent( vwep )
muzzleflash:SetColor(Vec4(1,0.6,0.0,1.0))
muzzleflash:SetPosition( displayposition )
muzzleflash:SetShadowMode(0)

HideMouse()
MoveMouse(GraphicsWidth()/2,GraphicsHeight()/2)
FlushKeys()
FlushMouse()

local pick
local camera = fw.main.camera
local remainingtime
local starttime=AppTime()
local gameduration=2--length of game in minutes
local gamemode=0

gunpos = vwep.position:Copy()

local smoothedgunswayamplitude= 0.0
local smoothedgunswayspeed = 0.0
local guntime = 0.0
local recoil = 0.0
local lastfiretime=0.0
local smoothrecoil=0.0
local swaydamping=0.0
local smoothswaydamping=0.0
local lightsmoothing =0.0
local gunlight = 0.0

--Flashlight
flashlight = {}
flashlight.light = CreateSpotLight(8)
flashlight.light:Hide()
flashlight.sound_switch = LoadSound("abstract::switch.wav")
flashlight.state=0
flashlight.light:SetConeAngles(30,35)
flashlight.light:SetRotation(Vec3(5,0,0))
flashlight.light:SetShadowmapSize(512)
flashlight.light:Paint(LoadMaterial("abstract::flashlight.mat"))

function flashlight:SetState( state )
       if state~=self.state then
               self.state=state
               if state==0 then
                       self.light:Hide()
               else
                       self.light:Show()
               end
               if self.sound_switch~=nil then
                       self.sound_switch:Play()
               end
       end
end


function ShootBullet( position, direction )
--      local speed=100.0
--      local pick = LinePick( position, Vec3(position.x+direction.x * speed) )
end


function DrawHUD(contr)
       SetBlend(BLEND_ALPHA)
       DrawText("pos: "..round(contr.position.x,3)..","..round(contr.position.y,3)..","..round(contr.position.z,3),1,FontHeight()*5)
       DrawText("rot: "..round(contr.rotation.x,3)..","..round(contr.rotation.y,3)..","..round(contr.rotation.z,3),1,FontHeight()*6)
       SetBlend(BLEND_NONE)
end


--main function
while KeyHit(KEY_ESCAPE)==0 do
       jump=KeyHit(KEY_SPACE)*6.0
       if controller:IsAirborne()==1 then jump=0 end


       local time = AppTime()/3200.0
       local frame = time*(179.0-96.0)+96.0
       frame=Clamp( frame, 96, 179 )
       vwep:Animate(96,1,0,1)


       --Camera look
       gx=Round(GraphicsWidth()/2)
       gy=Round(GraphicsHeight()/2)
       dx=Curve((MouseX()-gx)/4.0,dx,3.0/AppSpeed())
       dy=Curve((MouseY()-gy)/4.0,dy,3.0/AppSpeed())
       MoveMouse(gx,gy)
       camerapitch=camerapitch+dy
       camerayaw=camerayaw-dx
       camerapitch=math.min(camerapitch,89)
       camerapitch=math.max(camerapitch,-89)
       fw.main.camera:SetRotationf(camerapitch,camerayaw,0,1)

       movespeed=6
       movesmoothing=10
       if controller:IsAirborne()==1 then
               movesmoothing=200
       end

       --Player movement
       move=Curve( (KeyDown(KEY_W)-KeyDown(KEY_S))*movespeed,move,movesmoothing)
       strafe=Curve( (KeyDown(KEY_D)-KeyDown(KEY_A))*movespeed,strafe,movesmoothing)

       --Use objects
       if KeyHit(KEY_E)==1 then
               pick=CameraPick(camera,Vec3(GraphicsWidth()/2,GraphicsHeight()/2,2.0),0,0)
               if pick~=nil then
                       repeat
                               if pick.entity:GetClass()==ENTITY_MODEL then
                                       break
                               end
                               pick.entity=pick.entity.parent
                       until pick.entity==nil
                       if pick.entity~=nil then
                               pick.entity:SendMessage("use",controller,0)
                       end
               end
       end

--crouching
       if KeyHit(KEY_C)==1 then 
               if controller:IsCrouched()==1 then
                       crouch=0
                       cameraheight=1.7
               else
                       crouch=1
                       cameraheight=0.85
               end
       end

       --Update controller
       --controller:Update(camerayaw,move,strafe,jump,40,10)
       controller:Update(camerayaw,move,strafe,jump,40,10,crouch)

       fw:Update()

       if KeyHit(8)==1 then
         dofile("GUIindex.lua")
       end

       if KeyHit(KEY_F)==1 then
               flashlight:SetState(1-flashlight.state)
       end

       --Position camera
       camera:SetPositionf(controller.position.x,controller.position.y+cameraheight,controller.position.z,1)

       time=AppTime()
       gunfirefrequency=80
       gunswayspeed=0.001*20.0
       gunoffset = gunpos:Copy()
       gunswayamplitude = 0.02
       if KeyDown(KEY_W)==1 or KeyDown(KEY_D)==1 or KeyDown(KEY_A)==1 or KeyDown(KEY_S)==1 then
               gunswayamplitude = 0.03
               gunswayspeed=0.005*20.0
       end
       smoothedgunswayamplitude = Curve( gunswayamplitude, smoothedgunswayamplitude, 8.0  )
       smoothedgunswayspeed = Curve( gunswayspeed, smoothedgunswayspeed,8.0 )
       if smoothrecoil<0.001 then
               guntime = guntime + AppSpeed() * smoothedgunswayspeed * math.max(0.0,1.0 - smoothswaydamping)
       end
       gunoffset.z = gunoffset.z - smoothrecoil * 0.05
       smoothedgunswayamplitude = smoothedgunswayamplitude * (1.0 - smoothswaydamping)
       gunoffset.x = gunoffset.x + math.sin( guntime ) * smoothedgunswayamplitude * gunscale
       gunoffset.y = gunoffset.y + (1.0-math.cos( guntime*2.0 )) * 0.005 * gunscale * math.min(1.0,1.0 - smoothswaydamping)
       vwep:SetPosition( gunoffset )
       recoil = recoil-0.1
       swaydamping = math.max( swaydamping - 0.05, 0.0 )
       recoil = math.max(recoil,0.0)
       smoothrecoil=Curve(recoil,smoothrecoil,3.0)
       smoothswaydamping = Inc( swaydamping ,smoothswaydamping,0.01 )
       gunlight = math.max( gunlight- 0.2, 0.0 )
       lightsmoothing =gunlight-- Curve(gunlight,lightsmoothing,8.0)
       muzzleflash:SetColor(Vec4(1.0*lightsmoothing,0.6*lightsmoothing,0.0,1.0))
       if lightsmoothing <0.01 then
               muzzleflash:Hide()
       end
       if MouseDown(1)==1 then
               if AppTime()-lastfiretime>gunfirefrequency then
                       recoil = 1.0
                       lastfiretime=AppTime()+math.random(0,20)
                       gunswayspeed=0.0
                       gunlight = 1.0
                       source_gunshot:Play()
                       source_gunshot:SetPitch(1.0 + (math.random()-0.5)*0.05 )
                       swaydamping = 1.0
                       muzzleflash:Show()

                       CreateBullet(vwep:GetPosition(1) , fw.main.camera.mat:K():Scale(300))

               end
       end

       if MouseHit(2)==1 then
               phyproj = CreateBodyBox(1,1,1)
               projectile = CreateCube(phyproj)
               projectile:SetColor(Vec4(math.random(0,255)/255,math.random(0,255)/255,math.random(0,255)/255,1))

               phyproj:SetMass( 1 )
               phyproj:SetCollisionType(1,0) 

               local V = TFormVector(Vec3(0, 0, 2), fw.main.camera, nil)
               V = Vec3(fw.main.camera.position.x + V.x, fw.main.camera.position.y + V.y, fw.main.camera.position.z + V.z)
               PositionEntity(phyproj, V, 0)
               RotateEntity(phyproj, EntityRotation(fw.main.camera, 0), 0)
               phyproj:AddForcef(0, 100, 1500, 0)
       end 

       UpdateBullets()

       flashlight.light:SetPosition(fw.main.camera:GetPosition(1))
       flashlight.light:SetRotationf( CurveAngle( fw.main.camera.rotation.x, flashlight.light.rotation.x, 3.0/AppSpeed() ), CurveAngle( fw.main.camera.rotation.y, flashlight.light.rotation.y, 3.0/AppSpeed() ) )
       flashlight.light:Movef(-0.07,-0.04,0.02)

       fw:Render()

-- screenshot : note the second fw:Render()
if KeyDown(KEY_F12)==1 then
	SetBuffer(buffer)

	fw:Render()

	SetBuffer(buffer2)
	DrawImage(GetColorBuffer(buffer),0,0,buffer:Width(),buffer:Height())

	SetBuffer(BackBuffer())
	SaveBuffer(buffer2,"screenshot.png")

end

       DrawHUD(controller)

       Flip(0)
end

buffer=nil
buffer2=nil
controller:Free()
vwep:Free()

ShowMouse()

 

 

hth

[Mumbles]

I'm not quite sure what you mean.

 

to attach a TMesh to a TBody is done by setting the mesh's parent to the body.

 

EntityParent(Your Missile,your invisible body,1)

 

 

to then make the mesh "look in the same direction"

 

RotateEntity(Your missile,EntityRotation(invisible body,1),1)

 

 

 

And now the mesh will move with the bullet automatically...

[Josh]

For bullets I would perform a raycast each frame, and use AlignToVector to orient the visual mesh.

[Road Kill Kenny]

I'm not quite sure what you mean.

 

to attach a TMesh to a TBody is done by setting the mesh's parent to the body.

 

EntityParent(Your Missile,your invisible body,1)

 

 

to then make the mesh "look in the same direction"

 

RotateEntity(Your missile,EntityRotation(invisible body,1),1)

 

 

 

And now the mesh will move with the bullet automatically...

 

If you load the mesh and the body at 0,0,0 and then parent it and then position the body and fire it you shouldn't have to rotate the mesh to be in line. Provided that the body and the mesh match....

 

But I would recommend what Josh said anyway, align to vector would be the best way to go

[AnniXa]

You most likely dont need to calculate that since Le is all "entity-based" ...

you simply want to set the position / rotation of your bolt / bullet to the position / rotation of the body or set its complete EntityMatrix.

 

I took "all" the commands i would need to build game-subsystems from the command list and wrote samples for it.

It doesnt help much with integration the game-engine itself but game-mechanics can be extracted from it.

 

here is some, slightly changed, script metraton posted (dont know how to write that name though)

 

--stuff which should be part of LE
....

 

 

hth

 

Thank you very well for this clearifing example code!

 

I'm not quite sure what you mean.

 

to attach a TMesh to a TBody is done by setting the mesh's parent to the body.

 

EntityParent(Your Missile,your invisible body,1)

 

 

to then make the mesh "look in the same direction"

 

RotateEntity(Your missile,EntityRotation(invisible body,1),1)

 

 

 

And now the mesh will move with the bullet automatically...

 

I tried that, but since the body is not rotating well into the fly direction this not looked so good.

 

 

For bullets I would perform a raycast each frame, and use AlignToVector to orient the visual mesh.

 

 

If you load the mesh and the body at 0,0,0 and then parent it and then position the body and fire it you shouldn't have to rotate the mesh to be in line. Provided that the body and the mesh match....

 

But I would recommend what Josh said anyway, align to vector would be the best way to go

 

 

i think thats what i do now =)