Sun, Earth, Moon simulation with Entity System

**primo** · 08-10-2017, 16:47

demo using Entity System, it is almost impossible or very hard to do this in basic opengl, but Entity System makes simulations much easier

demo: sun, earth, moon system
tilted earth by 23, make a fake ball (MoonGuide) and position it on earth center and tilted it by 5.5 then rotate it
attach the moon to the MoonGuide
position a light on the center of the sun and make it look at the earth
https://en.wikipedia.org/wiki/Earth%...rth_season.jpg

'depending on example "TBGL_CustomSphereEntity" by Petr Schreiber, 2009                             =
'===============================================================================

Uses "TBGL" , "Math"

BEGIN CONST
  ' -- Scene IDs
  %sScene  = 1
  %texOne = 1
  ' -- Entity IDs 
  %eCamera = 1
  %eLight  
  
  %eSun
  %tSun       
  %eEarth
  %eMoonGuide
  %eMoon       
END CONST 

FUNCTION TBMAIN()
  LOCAL hWnd As DWORD
  Global FrameRate As Long
  Global ang, earthX, earthZ, OrbitRadius As Single
  Global flag, wireframe As Long
  flag = 1 
  OrbitRadius = 7.5
  
  ' -- Create and show window
  hWnd = TBGL_CreateWindowEx("press Space to toggle the camera position , 'W' to toggle wire/solid frame ", 800, 600, 32, %TBGL_WS_WINDOWED Or %TBGL_WS_CLOSEBOX) 
  TBGL_ShowWindow 
   
  ' -- Create scene
  TBGL_SceneCreate(%sScene)
  
  'TBGL_LoadTexture APP_Path+"SampleScripts\TBGL\GBuffers\Textures\Bricks.bmp", %texOne, %TBGL_TEX_MIPMAP
  ' -- Create basic entities
  ' -- Create camera to look from 0, 2, 7 to 0, 0, 0 
  TBGL_EntityCreateCamera(%sScene, %eCamera)
    TBGL_EntitySetPos(%sScene, %eCamera, 0, 0, -21)
    TBGL_EntitySetTargetPos(%sScene, %eCamera, 0, 0, 0)  
    
  ' -- Create point light  
  TBGL_EntityCreateLight(%sScene, %eLight)
  TBGL_EntitySetPos(%sScene, %eLight, 0, 0, 0)
  
  ' -- Create something to look at

  TBGL_EntityCreateFuncSlot(%sScene, %eSun, 0, "Sun_Render")
 
  TBGL_EntityCreateFuncSlot(%sScene, %eEarth, 0, "Earth_Render")
  TBGL_EntityTurn(%sScene, %eEarth, 0, 0, 23)  
    
    TBGL_EntityCreateFuncSlot(%sScene, %eMoonGuide, 0, "MoonGuide_Render")
    TBGL_EntityTurn(%sScene, %eMoonGuide, 0, 0, 5.5)
    TBGL_EntitySetPos(%sScene, %eMoonGuide, 0, 0, 0)
  
    
  TBGL_EntityCreateFuncSlot(%sScene, %eMoon, 0, "Moon_Render")
  'attach the moon to the blue ball inside the earth
  TBGL_EntityAttach(%sScene, %eMoon, %eMoonGuide, %TBGL_DEFAULT)
  
  ' -- Resets status of all keys 
  TBGL_ResetKeyState() 
  
  TBGL_EntitySetTexture(%sScene, %eEarth, %texOne )
  TBGL_LoadTexture APP_Path+"SampleScripts\TBGL\EntityBased\Textures\alien2.bmp", %texOne, %TBGL_TEX_MIPMAP 
  'TBGL_LoadTexture APP_Path+"SampleScripts\TBGL\GBuffers\Textures\Bricks.bmp", %texOne, %TBGL_TEX_MIPMAP
  TBGL_EntitySetColor(%sScene, %eEarth, 255, 255, 255)
  
  TBGL_PolygonLook %GL_FILL
  
  ' -- Main loop
  While TBGL_IsWindow(hWnd) 
    FrameRate = TBGL_GetFrameRate
    TBGL_SetWindowTitle( hWnd, "FPS =" +Str$(FrameRate)+"           press 'Space' to toggle the camera position , 'W' to toggle wire/solid frame")
    
    TBGL_ClearFrame 
    If TBGL_GetWindowKeyOnce( hWnd, %VK_SPACE) Then
    If flag = 1 Then
     TBGL_EntitySetPos(%sScene, %eCamera, 0, 30, -0.1)
     TBGL_EntitySetTargetPos(%sScene, %eCamera, 0, 0, 0)
     
     flag * -1  
     Else 
     TBGL_EntitySetPos(%sScene, %eCamera, 0, 0, -21)
     TBGL_EntitySetTargetPos(%sScene, %eCamera, 0, 0, 0) 
     flag * -1  
    End If
    End If
    
    If TBGL_GetWindowKeyOnce( hWnd, %VK_W) Then
    wireframe = Not wireframe
    TBGL_PolygonLook IIf(wireframe, %GL_LINE, %GL_FILL) 
    End If
       
    orbit()
    
    TBGL_SceneRender(%sScene)
   
    TBGL_DrawFrame 
 
    ' -- ESCAPE key to exit application
    If TBGL_GetWindowKeyState(hWnd, %VK_ESCAPE) Then Exit While 
  
  Wend 

  TBGL_DestroyWindow
END FUNCTION
 
Sub orbit()
ang + 0.4 ' determine the rotational speed
   earthX = OrbitRadius * Sin(DegToRad(ang)) ' FORMULA For the circular motion
   earthZ = OrbitRadius * Cos(DegToRad(ang)) ' FORMULA For the circular motion
   TBGL_EntitySetPos(%sScene, %eEarth, earthX, 0, earthZ)
   TBGL_EntitySetPos(%sScene, %eMoonGuide, earthX, 0, earthZ)
   TBGL_EntitySetTargetPos(%sScene, %eLight, earthX, 0, earthZ)
      
End Sub
        
' -- Render procedure  
Sub Earth_Render()
  TBGL_EntitySetColor(%sScene, %eEarth, 0, 255, 0)
    'TBGL_EntitySetTexture(%sScene, %eEarth, %texOne )    
  TBGL_EntitySetPos(%sScene, %eEarth, 0, 0, 0)
  TBGL_EntityTurn(%sScene, %eEarth, 0, 100/FrameRate, 0)
  
  ' -- earth represented by a sphere
  TBGL_Sphere 1.2
  TBGL_Translate 0,-1.8,0 
  TBGL_Cylinder 0.2,0.2,4 'earth axis
End Sub 

Sub Moon_Render()
  TBGL_EntitySetRot(%sScene, %eMoon, 0, 0, 0 )
  TBGL_EntityTurn(%sScene, %eMoon, 0, 100/FrameRate, 0)
  TBGL_EntitySetColor(%sScene, %eMoon, 255, 255, 155)    
  TBGL_EntitySetPos(%sScene, %eMoon, 3, 0, 0)
  TBGL_EntitySetScale(%sScene, %eMoon, 0.4, 0.4, 0.4) 
  ' -- Moon represented by a sphere
  TBGL_Sphere 1.2
  TBGL_Translate 0,-3.6,0
  TBGL_Cylinder 0.1,0.1,8 'moon axis
End Sub 

Sub Sun_Render()
      
  TBGL_EntitySetColor(%sScene, %eSun, 255, 255, 0) 
  'TBGL_EntitySetSpecular(%sScene, %eSun, 255, 0, 0 )
  TBGL_EntitySetPos(%sScene, %eSun, 0, 0, 0)
  TBGL_EntityTurn(%sScene, %eSun, 0, 40/FrameRate, 0)
  ' -- earth represented by a sphere 
  TBGL_UseLighting %FALSE  
  TBGL_Sphere 0.7
  TBGL_UseLighting %TRUE
End Sub

Sub MoonGuide_Render()
  TBGL_EntitySetColor(%sScene, %eMoonGuide, 255, 0, 255)
  TBGL_EntityTurn(%sScene, %eMoonGuide, 0, 100/FrameRate, 0)    
  ' -- MoonGuide represented by a sphere
  TBGL_Sphere 0.6
End Sub

demo: Moon phases:
very rough, but it show the idea, in the future i will try to reflect the real dimensions (scaled down)
position the camera on earth center (it should be at earth surface)
make the camera (the observer) look at the moon by tracking its positions

'depending on example "TBGL_CustomSphereEntity" by Petr Schreiber, 2009                             =
'===============================================================================

Uses "TBGL" , "Math"

BEGIN CONST
  ' -- Scene IDs
  %sScene  = 1
  %texOne = 1
  ' -- Entity IDs 
  %eCamera = 1
  %eLight  
  
  %eSun
  %tSun       
  %eEarth
  %eMoonGuide
  %eMoon       
END CONST 

FUNCTION TBMAIN()
  LOCAL hWnd As DWORD
  Global FrameRate As Long
  Global ang, earthX, earthZ, OrbitRadius, mX,mY,mZ As Single
  Global flag, wireframe As Long
  flag = 1 
  OrbitRadius = 7.5
  
  ' -- Create and show window
  hWnd = TBGL_CreateWindowEx("Moon Phases from the viewpoint of observer on earth  ", 800, 600, 32, %TBGL_WS_WINDOWED Or %TBGL_WS_CLOSEBOX) 
  TBGL_ShowWindow 
   
  ' -- Create scene
  TBGL_SceneCreate(%sScene)
  
  'TBGL_LoadTexture APP_Path+"SampleScripts\TBGL\GBuffers\Textures\Bricks.bmp", %texOne, %TBGL_TEX_MIPMAP
  ' -- Create basic entities
  ' -- Create camera to look from 0, 2, 7 to 0, 0, 0 
  TBGL_EntityCreateCamera(%sScene, %eCamera)
    TBGL_EntitySetPos(%sScene, %eCamera, 0, 0, -21)
    TBGL_EntitySetTargetPos(%sScene, %eCamera, 0, 0, 0)  
    
  ' -- Create point light  
  TBGL_EntityCreateLight(%sScene, %eLight)
  TBGL_EntitySetPos(%sScene, %eLight, 0, 0, 0)
  
  ' -- Create something to look at

  TBGL_EntityCreateFuncSlot(%sScene, %eSun, 0, "Sun_Render")
 
  TBGL_EntityCreateFuncSlot(%sScene, %eEarth, 0, "Earth_Render")
  TBGL_EntityTurn(%sScene, %eEarth, 0, 0, 23)  
    
    TBGL_EntityCreateFuncSlot(%sScene, %eMoonGuide, 0, "MoonGuide_Render")
    TBGL_EntityTurn(%sScene, %eMoonGuide, 0, 0, 5.5)
    TBGL_EntitySetPos(%sScene, %eMoonGuide, 0, 0, 0)
  
    
  TBGL_EntityCreateFuncSlot(%sScene, %eMoon, 0, "Moon_Render")
  'attach the moon to the blue ball inside the earth
  TBGL_EntityAttach(%sScene, %eMoon, %eMoonGuide, %TBGL_DEFAULT)
    
  ' -- Resets status of all keys 
  TBGL_ResetKeyState() 
  
  TBGL_EntitySetTexture(%sScene, %eEarth, %texOne )
  TBGL_LoadTexture APP_Path+"SampleScripts\TBGL\EntityBased\Textures\alien2.bmp", %texOne, %TBGL_TEX_MIPMAP 
  'TBGL_LoadTexture APP_Path+"SampleScripts\TBGL\GBuffers\Textures\Bricks.bmp", %texOne, %TBGL_TEX_MIPMAP
  TBGL_EntitySetColor(%sScene, %eEarth, 255, 255, 255)
  
  TBGL_PolygonLook %GL_FILL
  
  ' -- Main loop
  While TBGL_IsWindow(hWnd) 
    FrameRate = TBGL_GetFrameRate
    TBGL_SetWindowTitle( hWnd, "FPS =" +Str$(FrameRate)+"   Moon Phases from the viewpoint of observer on earth")
    
    TBGL_ClearFrame 
        
    orbit()
    
    TBGL_SceneRender(%sScene)
   
    TBGL_DrawFrame 
 
    ' -- ESCAPE key to exit application
    If TBGL_GetWindowKeyState(hWnd, %VK_ESCAPE) Then Exit While 
  
  Wend 

  TBGL_DestroyWindow
END FUNCTION
 
Sub orbit()
ang + 0.4 ' determine the rotational speed
   earthX = OrbitRadius * Sin(DegToRad(ang)) ' FORMULA For the circular motion
   earthZ = OrbitRadius * Cos(DegToRad(ang)) ' FORMULA For the circular motion
   TBGL_EntitySetPos(%sScene, %eEarth, earthX, 0, earthZ)
   TBGL_EntitySetPos(%sScene, %eMoonGuide, earthX, 0, earthZ)
   TBGL_EntitySetTargetPos(%sScene, %eLight, earthX, 0, earthZ)
   TBGL_EntitySetPos(%sScene, %eCamera, earthX, 0.0, earthZ)
   TBGL_EntityGetPos( %sScene, %eMoon, mx, my, mz, %TRUE)
   TBGL_EntitySetTargetPos(%sScene, %eCamera,  mX, mY, mZ)
      
End Sub
        
' -- Render procedure  
Sub Earth_Render()
  TBGL_EntitySetColor(%sScene, %eEarth, 0, 255, 0)
  TBGL_EntitySetPos(%sScene, %eEarth, 0, 0, 0)
  TBGL_EntityTurn(%sScene, %eEarth, 0, 100/FrameRate, 0)
  ' -- earth represented by a sphere
  TBGL_Sphere 0.01
 
End Sub 

Sub Moon_Render()
  TBGL_EntitySetRot(%sScene, %eMoon, 0, 0, 0 )
  TBGL_EntityTurn(%sScene, %eMoon, 0, 100/FrameRate, 0)
  TBGL_EntitySetColor(%sScene, %eMoon, 255, 255, 155)    
  TBGL_EntitySetPos(%sScene, %eMoon, 3, 0, 0)
  TBGL_EntitySetScale(%sScene, %eMoon, 0.4, 0.4, 0.4) 
  ' -- Moon represented by a sphere
  TBGL_Sphere 1.2
  TBGL_Translate 0,-3.6,0
  TBGL_Cylinder 0.1,0.1,8 'moon axis
End Sub 

Sub Sun_Render()
      
  TBGL_EntitySetColor(%sScene, %eSun, 255, 255, 0) 
  'TBGL_EntitySetSpecular(%sScene, %eSun, 255, 0, 0 )
  TBGL_EntitySetPos(%sScene, %eSun, 0, 0, 0)
  TBGL_EntityTurn(%sScene, %eSun, 0, 40/FrameRate, 0)
  ' -- earth represented by a sphere 
  TBGL_UseLighting %FALSE  
  TBGL_Sphere 0.09
  TBGL_UseLighting %TRUE
End Sub

Sub MoonGuide_Render()
  TBGL_EntitySetColor(%sScene, %eMoonGuide, 255, 0, 255)
  TBGL_EntityTurn(%sScene, %eMoonGuide, 0, 50/FrameRate, 0)    
  ' -- MoonGuide represented by a sphere
  TBGL_Sphere 0.001
End Sub

a joke i read:
Which is more important, the sun or the moon, in giving us light?" A little boy asked his teacher.
"It must be the moon," the teacher answered.
Boy: Why?
Teacher: Because the moon shines at night, when it is dark.
ref : http://idv.sinica.edu.tw/jwang/

**Petr Schreiber** · 08-10-2017, 21:51

Dear Primo,

you made my day. Excellent example, thanks for sharing!

Petr

**Petr Schreiber** · 09-10-2017, 17:36

Did you know?

You can improve the quality of the primitives by manipulating it this way:

tbgl_setprimitivequality 100

Use this parameter wisely, it leads to increased polycount

Petr

**Petr Schreiber** · 09-10-2017, 17:41

How to ensure the animation will reach roughly the same speed on any PC?

Scale the movement/rotations by the frame rate.

For example, if you want something to turn 360° in one second, you can do:

tbgl_entityTurn(%scene, %something, 0, 360/FrameRate, 0)

If you perform PC performance dependant additions like:

angle + 0.4 ' equivalent of angle += 0.4, or angle = angle + 0.4

...it will result in varied performance on slower and faster PC.

If you approach it like:

angle + 360/FrameRate

... it will ensure angle will reach 360 in +/- one second on any PC.

Petr

**primo** · 09-10-2017, 21:21

Thanks Petr for the tips, yes i have noticed the rough sphere in the moon phases example, this will help in the future more realistic moon phases demo, i have tried it like this:
TBGL_PushMatrix
TBGL_SetPrimitiveQuality 100
TBGL_Sphere 1.2
TBGL_PopMatrix
TBGL_SetPrimitiveQuality 24