tbgl_EntityCreateCamera- Question

[ReneMiner]

How can I get the coordinates where the %ENT_CAMERA-Entity currently is looking at?

(TBGL_Demo06_01_MovingIn3D_UsingEntitySystemBasic.tBasic from sampleScripts\TBGL\Basic-folder)
and btw. what is "dim Sheeps as Long" for? Some internal switch?


The intention is, to move some mesh or tirangle-list through space and make the camera look at it.
But camera should be moveable in all directions around the mesh, always looking at it
so maybe normal controls (left/right/up/down/pgUp/pgDn) refer to the meshes movement, camera will always follow, so makes the same moves

but if I press any Shift-Key just the camera should
%VL_Left - rotate left around point of view (my mesh)
%VK_Up - get closer
%VK_Down- zoom out
%VK_PgUp - Camera shall move upwards but still look down to the mesh

so I need to know: How can I get or even set the look-at-position for the camera-entity

and another question: how can I make my Triangle-Lists triangles, which I setup with

TBGL_NewList %ENT_POINTER
TBGL_BeginPoly %GL_TRIANGLES
TBGL_Color 0, 127, 0
TBGL_Vertex -1 , 0 , 0
TBGL_Normal
...etc.

to be rendered just from one side visible?

[Petr Schreiber]

Hi Rene,

#1
The sheeps shouldn't be there :P I sometimes use this variable to count frames of animation, and once the count is elapsed, I do something and reset it again. (for example when updating window title with framerate)

#2
The camera position is set using TBGL_EntitySetPos, as with any other entity. To make camera look at some place, you need to call TBGL_EntitySetTarget or TBGL_EntitySetTargetPos.
In case the target is moving, you might want to call it each frame.

For example, to make camera look at box, you just need to do this:

TBGL_EntitySetTarget(%sScene, %eCamera, %eBox)

If you want the camera to be placed at fixed offset from the object, you can "stick" the camera to object using parent-child relationship.

' -- Stick camera to the box      
TBGL_EntitySetParent   ( %sScene, %eCamera, %eBox)
' -- Now these are relative to the box
TBGL_EntitySetPos      ( %sScene, %eCamera, 0, 2, 4 )
TBGL_EntitySetTargetPos( %sScene, %eCamera, 0, 0, 0 )

And finally, if you want something like chase camera in racing games, you keep the objects separate, and dynamically position the camera:

' -- Make camera look at box   
distance = TBGL_EntityGetDistance(%sScene, %eCamera, %eBox)
TBGL_EntitySetTarget(%sScene, %eCamera, %eBox)

' -- If we are far enought...
If distance > 3 Then         
  ' -- We push the camera towards the box                 
  TBGL_EntityPush(%sScene, %eCamera, 0, 0, (distance-3) / frameRate)
  
  ' -- Testing if camera didn't fall to low
  TBGL_EntityGetPos(%sScene, %eCamera, x, y, z)        
  If y < 2 Then ' -- Camera too low
    TBGL_EntityMove(%sScene, %eCamera, 0, 2-y, 0)
  End If
End If

#3
To make triangles visible from just one side, you need to enable culling. It is not present in TBGL by default, but you can mix TBGL with native OpenGL.
So, first add this on top of your script:

#include "thinbasic_gl.inc"

Then in your code:

glEnable(%GL_CULL_FACE)
glCullFace(%GL_BACK) ' -- Or GL_FRONT, depends what you want to achieve

' -- Define your triangles here

glDisable(%GL_CULL_FACE)

Petr

[ReneMiner]

OK, I'll just show you, what I'm up to. It's supposed to become a basic 3d-Mesh-Editor
I know how to dimension all that stuff and creating, drawing but I got problems with them movement-controls, they drive me crazy
the only that work is pgUp & pgDn
Also do I experience the light just flickers for a short second.

EDIT: -done-

EDIT2: Culling does not seem to work - or did I put it the wrong place?

[Petr Schreiber]

Hi Rene,

I need to go offline to prepare to work for this week, but this example should get you started.

The main idea is to have two pivots in the origin of coordinates - one for left/right rotations, another for up/down rotations.

%eCameraPivotLR is the base
%eCameraPivotUD is child of %eCameraPivotLR
%eVirtualCameraBody is child of %eCameraPivotUD
and finally, %eCamera is child of %eVirtualCameraBody

Here is sample code:
set %visualizeCameraMovement = true to see how it works
set %visualizeCameraMovement = false to see the camera in action

' -- Camera on orbit

%visualizeCameraMovement = TRUE ' -- Set to false to see through eyes of camera

'---Load needed modules
Uses "TBGL"

Begin Const  
  ' -- Scenes
  %sScene = 1
  
  ' -- Entities
  %eCameraPivotLR = 1
  %eCameraPivotUD

  %eCamera   
  %eLight    
  %eGridList 
  %eBox    
  %eVirtualCameraBody    
  
End Const
  
Function TBMain()
  Dim hWnd As Dword
  
  '---Creates OpenGL window and returns handle
  hWnd = TBGL_CreateWindowEx("Camera for editor, use arrows and pageup/pagedown - press ESC to quit", 640, 480, 32, %TBGL_WS_WINDOWED )
  '---Shows TBGL window
  TBGL_ShowWindow

  ' -- First we will create world as place to contain entities
  tbgl_SceneCreate(%sScene) 
  ' -- Camera pivot
  TBGL_EntityCreatePivot( %sScene, %eCameraPivotLR)
  TBGL_EntityCreatePivot( %sScene, %eCameraPivotUD, %eCameraPivotLR)
  
  ' -- Camera
  TBGL_EntityCreateCamera( %sScene, %eCamera) ' -- Camera becomes parent of pivot
  If %visualizeCameraMovement Then
    ' -- We set our eyes somewhere to look better on subject
    TBGL_EntitySetPos      ( %sScene, %eCamera, 0, 10,10 )
  Else  
    ' -- We shift camera slightly to not appear inside virtual camera
    TBGL_EntitySetPos      ( %sScene, %eCamera, 0, 0, -0.55 )
  End If      

  ' -- Light  
  TBGL_EntityCreateLight(%sScene, %eLight)
  TBGL_EntitySetPos(%sScene, %eLight, 15, 10, 5)
  TBGL_EntitySetColor(%sScene, %eLight, 255, 255, 255)
  
  ' -- Grid
  TBGL_EntityCreateDLSlot( %sScene, %eGridList, 0, CreateGridAsDList() )
  
  ' -- Box
  TBGL_EntityCreateBox( %sScene, %eBox, 0, 1, 1, 1 )
  TBGL_EntityCreateBox( %sScene, %eVirtualCameraBody, %eCameraPivotUD, 0.1, 0.3, 1 )
  TBGL_EntitySetColor( %sScene, %eVirtualCameraBody, 255, 128, 0 )
  TBGL_EntitySetPos(%sScene, %eVirtualCameraBody, 0, 0, 5)
  
  If %visualizeCameraMovement = FALSE Then
    ' -- Stick camera to virtual camera body
    TBGL_EntitySetParent(%sScene, %eCamera, %eVirtualCameraBody)
  End If  

  dim FrameRate as double
  
  '---Resets key status before checking
  TBGL_ResetKeyState()

  '---Main script loop
  WHILE TBGL_IsWindow(hWnd)
  
    '---Script will run on different PCs so we must assure
    '---constant speed of movement by scaling movements relative to frame rate
    FrameRate = TBGL_getFrameRate
    
    '---Prepares clear frame
    TBGL_ClearFrame         
      
      ' -- Make camera look at box
      TBGL_EntitySetTarget(%sScene, %eCamera, %eBox)

      tbgl_SceneRender(%sScene)

    TBGL_DrawFrame                    ' Swaps the buffers - displays rendered image

    If TBGL_GetWindowKeyState( hWnd, %VK_UP)     Then TBGL_EntityPush(%sScene, %eVirtualCameraBody, 0, 0, -5/FrameRate) ' -- Move camera closer
    If TBGL_GetWindowKeyState( hWnd, %VK_DOWN)   Then TBGL_EntityPush(%sScene, %eVirtualCameraBody, 0, 0,  5/FrameRate)

    If TBGL_GetWindowKeyState( hWnd, %VK_LEFT)   Then TBGL_EntityTurn(%sScene, %eCameraPivotLR, 0, -90/FrameRate, 0)    ' -- Rotate Left-Right pivot
    If TBGL_GetWindowKeyState( hWnd, %VK_RIGHT)  Then TBGL_EntityTurn(%sScene, %eCameraPivotLR, 0,  90/FrameRate, 0)    
    
    If TBGL_GetWindowKeyState( hWnd, %VK_PGUP)   Then TBGL_EntityTurn(%sScene, %eCameraPivotUD, -90/FrameRate, 0, 0)    ' -- Rotate Up-Down pivot
    If TBGL_GetWindowKeyState( hWnd, %VK_PGDN)   Then TBGL_EntityTurn(%sScene, %eCameraPivotUD,  90/FrameRate, 0, 0)
                                                                            
    if TBGL_GetwindowKeyState( hWnd, %VK_ESCAPE) then EXIT WHILE

  WEND

  '---Closes OpenGL window
  TBGL_DestroyWindow
End Function

Function CreateGridAsDList() As Long  ' Returns to which display list we save
  local i, j as long
  
  TBGL_NewList 1
    TBGL_UseLighting FALSE
      '---Let's build a grid
      TBGL_BeginPoly %GL_LINES          ' Starts polygon definition based on 2 vertex lines
        TBGL_Color 0,255,0              ' Defines color
  
        For i = -10 To 10
          For j = -10 To 10
            TBGL_Vertex -10, 0,   j     ' Adds vertex
            TBGL_Vertex  10, 0,   j     ' Adds vertex
  
            TBGL_Vertex  i,  0, -10     ' Adds vertex
            TBGL_Vertex  i,  0,  10     ' Adds vertex
  
          Next
        Next
  
      TBGL_EndPoly                 
      TBGL_UseLighting TRUE
  tbgl_EndList 
  
  function = 1 
End Function

I hope it helps! Must run now, bye bye!


Petr

[ReneMiner]

I'm still sitting here and cranking my brain at 3:00 in the morning, I'm on edge of a major life crisis and almost about to throw something into that monitor in front of me.

Edit at 5:00
finally I got it. with just one pivot, no virtualCameraBody and no radians but a good old projection-table in degrees