OpenGL Gadget: How to make mesh edges more defined?

[IdeasVacuum]

I have spent way too much time trying to get a better definition of mesh (STL) edges.
So far I have been testing with glMaterialfv() plus a light (or two) but with no success.

I think I need a Shader to achieve this, but how?

Below is a screenshot from a CAD program that gets it right:

[Samuel]

What does the mesh look like in your software? I'm guessing you might have incorrect vertex normals. That or not enough normals per vertex location for flat shading.

The STL format isn't a great format for light data. Some software export STLs with the normal parameter defining if the triangle is using the right or left hand rule (eg. (Tri1, Tri2, Tri3) or (Tri1, Tri3, Tri2)). Then other software will export them with the triangles normal vector (eg. (1.0, 0.0, 0.0)).
Personally, I wouldn't rely on the STL's normal data and just calculate it myself when importing the file.

[IdeasVacuum]

Hi Samuel

You are right. The actual STL Standard calls for a single normal per triangle face. That is the type of (Binary) STL I am receiving but indeed some faces are inside-out. However, if I ignore the STL normal and calc my own, the result is pretty much the same! I think it's possible that those areas have two identical triangles in the same place, not sure. Nevertheless, I can't get the "good" edges to be prominent.

[Samuel]

Does every vertex have a normal assigned to it?

I'd also debug the normals to make sure they are correct. For that specific mesh the face normals should match the axis they are looking down. For example any triangle that is looking down the positive X axis should have vertex normals that are (1.0,0.0,0.0). And if they are looking down the negative Y axis then the normals would be (0.0,-1.0,0.0). etc...

[IdeasVacuum]

Hi Samuel

Ah:

Does every vertex have a normal assigned to it?

I was unsure about that, some online OpenGL tutorials contravening others. So currently, my code has one normal per triangle face, as per the STL itself. I'll change it. The normal directions do check out correctly for the sample mesh.

[applePi]

me too have only something like

Code: Select all

facet normal 0.468282 -0.863498 -0.187306

in all stl models i have. so the spider looks like

in Fill mode:

Code: Select all

glPolygonMode_(#GL_FRONT_AND_BACK, #GL_FILL )

i have used this lighting and other things to light the models , i copied it from another code, the light positions needs corrections .you can add it after OpenGLGadget definition

Code: Select all

Global Dim LightPos.f(4) ;Light Position
 LightPos(0)= 0.0 : LightPos(1)= 15.0 : LightPos(2)=-40.0 : LightPos(3)= 10.0
Global Dim LightAmb.f(4) ;Ambient Light Values
 LightAmb(0)= 0.2 : LightAmb(1)= 0.2 : LightAmb(2)= 0.2 : LightAmb(3)= 1.0
Global Dim LightDif.f(4) ;Diffuse Light Values
 LightDif(0)= 0.6 : LightDif(1)= 0.6 : LightDif(2)= 0.6 : LightDif(3)= 1.0
Global Dim LightSpc.f(4) ;Specular Light Values
LightSpc(0)=-0.2 : LightSpc(1)=-0.2 : LightSpc(2)=-0.2 : LightSpc(3)= 1.0

Global Dim MatAmb.f(4) ;Material - Ambient Values
 MatAmb(0)= 0.4 : MatAmb(1)= 0.4 : MatAmb(2)= 0.4 : MatAmb(3)= 1.0
Global Dim MatDif.f(4) ;Material - Diffuse Values
 MatDif(0)= 1.2 : MatDif(1)= 0.6 : MatDif(2)= 0.0 : MatDif(3)= 1.0
Global Dim MatSpc.f(4) ;Material - Specular Values
 MatSpc(0)= 0.0 : MatSpc(1)= 0.0 : MatSpc(2)= 0.0 : MatSpc(3)= 1.0
Global Dim MatShn.f(1) ;Material - Shininess
MatShn(0)= 0.0


glClearColor_ (0.0, 0.0, 0.0, 0.0);
glShadeModel_ (#GL_SMOOTH)

glEnable_(#GL_LIGHTING);
glEnable_(#GL_LIGHT0);
glEnable_(#GL_DEPTH_TEST);

glLightfv_(#GL_LIGHT1,#GL_POSITION,LightPos()) ;Set Light1 Position
glLightfv_(#GL_LIGHT1,#GL_AMBIENT,LightAmb()) ;Set Light1 Ambience
glLightfv_(#GL_LIGHT1,#GL_DIFFUSE,LightDif()) ;Set Light1 Diffuse
glLightfv_(#GL_LIGHT1,#GL_SPECULAR,LightSpc()) ;Set Light1 Specular
glEnable_(#GL_LIGHT1) ;Enable Light1
glEnable_(#GL_LIGHTING) ;Enable Lighting
 
glMaterialfv_(#GL_FRONT,#GL_AMBIENT,MatAmb()) ;Set Material Ambience
glMaterialfv_(#GL_FRONT,#GL_DIFFUSE,MatDif()) ;Set Material Diffuse
glMaterialfv_(#GL_FRONT,#GL_SPECULAR,MatSpc()) ;Set Material Specular
glMaterialfv_(#GL_FRONT,#GL_SHININESS,MatShn());Set Material Shininess

[IdeasVacuum]

Hi ApplePi

Yep - those are generally the light settings etc that I have been experimenting with. If the Mesh was a cube with each face being a quad, no problem, just like the many tutorials on the Internet. But if a "face" actually consists of many irregular triangles, there are all sorts of problems because, using those lighting functions (and Material), the light values are applied to each individual triangle. So, in the tutorials (quads cube) getting edge definition is easy - just adjust the light diffusion. I can't get near it with real-world meshes.

I get the impression from my tests that using a texture would be better, but possibly needs a shader to get that edge definition.

I'm currently putting together a "stand alone" example in the hope that someone on the forum knows how to do it. The mesh is the smallest real-world example I have and has 61,640 faces

[Samuel]

Shaders won't make much of a difference if there is something wrong with the object's data.

I'm thinking your file has errors or there might be a mistake in your normal calculations. Because I don't seem to have the same problems with Stl files that you are having.
I threw together a simple Stl importer(only works with Stl's ascii files) that might be of some use to you.

You may need to change ZoomFactor depending on your objects size.

Code: Select all

EnableExplicit

;-STRUCTURES
Structure Long3
  X.l
  Y.l
  Z.l
EndStructure

Structure Vector3
  X.f
  Y.f
  Z.f
EndStructure

Structure ObjectData
  Handle.b
  VertexCTR.l
  VertexLimit.l
  Array Vertex.Vector3(0)
  Array Normal.Vector3(0)
  TriangleCTR.l
  TriangleLimit.l
  Array Triangle.Long3(0)
EndStructure

;-DECLARES
Declare ImportStl(Path.s)
Declare Render()
Declare SetupGL()

Declare MATH_Normalize3D(*Value.Vector3)
Declare MATH_TriangleNormal(*V1.Vector3, *V2.Vector3, *V3.Vector3, *Result.Vector3)

;-DEFINES AND GLOBALS
Define.l Event
Define.l Quit

Global.ObjectData Object

Global.f RollAxisX
Global.f RollAxisY
Global.f RollAxisZ

Global.f RotateSpeedX = 0.0
Global.f RotateSpeedY = 1.0
Global.f RotateSpeedZ = 1.0

Global.f ZoomFactor = -10.0 ;Decrease value to zoom out.

;-MAIN WINDOW
OpenWindow(0, 0, 0, 800, 600, "Stl file import", #PB_Window_SystemMenu | #PB_Window_ScreenCentered)

OpenGLGadget(0, 0, 0, 800, 600)
SetupGL()

If ImportStl("Test.stl") = #False
  MessageRequester("Error", "Failed to import object.")
  End
EndIf

;-MAIN REPEAT
Repeat
  
  Repeat
    Event = WindowEvent()
    
    If Event = #PB_Event_CloseWindow
      Quit = 1
    EndIf
  Until Event = 0
  
  Render()
  
Until Quit = 1
End

;-
;-PROCEDURES
Procedure ImportStl(Path.s)
  
  Define.l Epos
  Define.l File
  Define.l Spos
  
  Define.s Result
  Define.s String
  
  Define.Vector3 Normal
  
  ;Make sure file exists.
  File = ReadFile(#PB_Any, Path)
  If IsFile(File) = 0
    ProcedureReturn #False
  EndIf
  
  ;Begin File Reading
  With Object
    \Handle = 1
    
    While Eof(File) = 0
      Result = ReadString(File, #PB_Ascii)
      
      ;Find triangles
      If Mid(Result, 0, 5) = "facet"
        ;Collect triangle's data
        While Eof(File) = 0
          Result = ReadString(File, #PB_Ascii)
          
          If Mid(Result, 0, 6) = "vertex"
            ;Found vertex data
            If \VertexCTR + 1 >= \VertexLimit
              \VertexLimit + 1000
              ReDim \Vertex(\VertexLimit)
              ReDim \Normal(\VertexLimit)
            EndIf
            
            \VertexCTR + 1
            
            Spos = 8
            Epos = FindString(Result, " ", Spos)
            String = Mid(Result, Spos, Epos-Spos)
            \Vertex(\VertexCTR)\X = ValF(String)
            Spos = Epos + 1
            
            Epos = FindString(Result, " ", Spos)
            String = Mid(Result, Spos, Epos-Spos)
            \Vertex(\VertexCTR)\Y = ValF(String)
            Spos = Epos + 1
            
            Epos = FindString(Result, " ", Spos)
            String = Mid(Result, Spos)
            \Vertex(\VertexCTR)\Z = ValF(String)
          EndIf
          
          ;Found end of triangle
          If Mid(Result, 0, 8) = "endfacet"
            ;Store Triangle data
            If \TriangleCTR + 1 >= \TriangleLimit
              \TriangleLimit + 1000
              ReDim \Triangle(\TriangleLimit)
            EndIf
            
            \TriangleCTR + 1
            
            \Triangle(\TriangleCTR)\X = \VertexCTR-2
            \Triangle(\TriangleCTR)\Y = \VertexCTR-1
            \Triangle(\TriangleCTR)\Z = \VertexCTR
            
            ;Calculate triangle's normal
            MATH_TriangleNormal(@\Vertex(\VertexCTR-2), @\Vertex(\VertexCTR-1), @\Vertex(\VertexCTR), @Normal)
            \Normal(\VertexCTR-2)\X = Normal\X
            \Normal(\VertexCTR-2)\Y = Normal\Y
            \Normal(\VertexCTR-2)\Z = Normal\Z
            
            \Normal(\VertexCTR-1)\X = Normal\X
            \Normal(\VertexCTR-1)\Y = Normal\Y
            \Normal(\VertexCTR-1)\Z = Normal\Z
            
            \Normal(\VertexCTR)\X   = Normal\X
            \Normal(\VertexCTR)\Y   = Normal\Y
            \Normal(\VertexCTR)\Z   = Normal\Z
            
            Break
          EndIf
        Wend
        
        Continue
      EndIf
    Wend
  EndWith

  ProcedureReturn #True
  
EndProcedure

Procedure Render()
  
  Define.l TriCTR
  Define.l VCTR1, VCTR2, VCTR3
  
  Define.Vector3 Nor1, Nor2, Nor3
  Define.Vector3 Vec1, Vec2, Vec3
  
  SetGadgetAttribute(0, #PB_OpenGL_SetContext, #True)
  
  glPushMatrix_()                  ; Save the original Matrix coordinates
  glMatrixMode_(#GL_MODELVIEW)

  glTranslatef_(0, 0, ZoomFactor)  ;  move the camera out

  glRotatef_(RollAxisX, 1.0, 0, 0) ; rotate around X axis
  glRotatef_(RollAxisY, 0, 1.0, 0) ; rotate around Y axis
  glRotatef_(RollAxisZ, 0, 0, 1.0) ; rotate around Z axis
 
  RollAxisX + RotateSpeedX 
  RollAxisY + RotateSpeedY 
  RollAxisZ + RotateSpeedZ 

  ; clear color and depth buffers
  glClearColor_(0.2, 0.4, 0.6, 1.0)
  glClear_(#GL_COLOR_BUFFER_BIT | #GL_DEPTH_BUFFER_BIT)
  
  With Object
    If \Handle = 1
      glEnable_(#GL_LIGHTING)
      glEnable_(#GL_LIGHT0)
      glBegin_(#GL_TRIANGLES)
      
      For TriCTR = 1 To \TriangleCTR
        VCTR1 = \Triangle(TriCTR)\X
        VCTR2 = \Triangle(TriCTR)\Y
        VCTR3 = \Triangle(TriCTR)\Z
        
        Vec1\X = \Vertex(VCTR1)\X
        Vec1\Y = \Vertex(VCTR1)\Y
        Vec1\Z = \Vertex(VCTR1)\Z
        Nor1\X = \Normal(VCTR1)\X
        Nor1\Y = \Normal(VCTR1)\Y
        Nor1\Z = \Normal(VCTR1)\Z
        
        Vec2\X = \Vertex(VCTR2)\X
        Vec2\Y = \Vertex(VCTR2)\Y
        Vec2\Z = \Vertex(VCTR2)\Z
        Nor2\X = \Normal(VCTR2)\X
        Nor2\Y = \Normal(VCTR2)\Y
        Nor2\Z = \Normal(VCTR2)\Z
        
        Vec3\X = \Vertex(VCTR3)\X
        Vec3\Y = \Vertex(VCTR3)\Y
        Vec3\Z = \Vertex(VCTR3)\Z
        Nor3\X = \Normal(VCTR3)\X
        Nor3\Y = \Normal(VCTR3)\Y
        Nor3\Z = \Normal(VCTR3)\Z
        
        glNormal3f_(Nor1\X, Nor1\Y, Nor1\Z)
        glVertex3f_(Vec1\X, Vec1\Y, Vec1\Z)
        
        glNormal3f_(Nor2\X, Nor2\Y, Nor2\Z)
        glVertex3f_(Vec2\X, Vec2\Y, Vec2\Z)
        
        glNormal3f_(Nor3\X, Nor3\Y, Nor3\Z)
        glVertex3f_(Vec3\X, Vec3\Y, Vec3\Z)
      Next
      glEnd_()
    EndIf
  EndWith

  glPopMatrix_()
  glFinish_()

  SetGadgetAttribute(0, #PB_OpenGL_FlipBuffers, #True)
  
EndProcedure

Procedure SetupGL()
    
  glMatrixMode_(#GL_PROJECTION)
  gluPerspective_(30.0, 800/600, 1.0, 1000.0) 
  
  ; position viewer
  glMatrixMode_(#GL_MODELVIEW)
  
  glTranslatef_(0, 0, -5.0)
  
  glEnable_(#GL_DEPTH_TEST)
  
  glEnable_(#GL_CULL_FACE)
  
  glShadeModel_(#GL_SMOOTH)
  
EndProcedure

;-
;-MATH PROCEDURES
Procedure MATH_Normalize3D(*Value.Vector3)
  
  Define.d Length
  
  Length = Sqr(*Value\X * *Value\X + *Value\Y * *Value\Y + *Value\Z * *Value\Z)
  If Length = 0
    Length = 1
  EndIf
  
  *Value\X = *Value\X / Length
  *Value\Y = *Value\Y / Length
  *Value\Z = *Value\Z / Length

EndProcedure

Procedure MATH_TriangleNormal(*V1.Vector3, *V2.Vector3, *V3.Vector3, *Result.Vector3)
  
  *Result\X = (*V1\Y - *V2\Y) * (*V2\Z - *V3\Z) - (*V1\Z - *V2\Z) * (*V2\Y - *V3\Y)
  *Result\Y = (*V1\Z - *V2\Z) * (*V2\X - *V3\X) - (*V1\X - *V2\X) * (*V2\Z - *V3\Z)
  *Result\Z = (*V1\X - *V2\X) * (*V2\Y - *V3\Y) - (*V1\Y - *V2\Y) * (*V2\X - *V3\X)
  
  MATH_Normalize3D(*Result)
  
EndProcedure

[IdeasVacuum]

Hi Samuel

Thanks for your help. A major part of the issue is - I'm running out of coffee.

I have made an Ascii STL, verified it in Mesh_Lab and Space_Claim. Can't see it with your code however - I have tried tweaking the ZoomFactor.

Sample Ascii STL on my website:

https://www.professorcad.co.uk/download.html

[IdeasVacuum]

... actually there might be a code typo somewhere? This small ASCII STL does not work either:

https://people.sc.fsu.edu/~jburkardt/da ... teapot.stl

[Samuel]

Sorry about that, I forgot to LTrim() the string data in the importer. I also updated the ortho matrix and ZoomFactor to better fit your first model.

Code: Select all

EnableExplicit
;-STRUCTURES
Structure Long3
  X.l
  Y.l
  Z.l
EndStructure

Structure Vector3
  X.f
  Y.f
  Z.f
EndStructure

Structure ObjectData
  Handle.b
  VertexCTR.l
  VertexLimit.l
  Array Vertex.Vector3(0)
  Array Normal.Vector3(0)
  TriangleCTR.l
  TriangleLimit.l
  Array Triangle.Long3(0)
EndStructure

;-DECLARES
Declare ImportStl(Path.s)
Declare Render()
Declare SetupGL()

Declare MATH_Normalize3D(*Value.Vector3)
Declare MATH_TriangleNormal(*V1.Vector3, *V2.Vector3, *V3.Vector3, *Result.Vector3)

;-DEFINES AND GLOBALS
Define.l Event
Define.l Quit

Global.ObjectData Object

Global.f RollAxisX
Global.f RollAxisY
Global.f RollAxisZ

Global.f RotateSpeedX = 0.0
Global.f RotateSpeedY = 1.0
Global.f RotateSpeedZ = 1.0

Global.f ZoomFactor = -1000.0 ;Decrease value to zoom out.

;-MAIN WINDOW
OpenWindow(0, 0, 0, 800, 600, "Stl file import", #PB_Window_SystemMenu | #PB_Window_ScreenCentered)

OpenGLGadget(0, 0, 0, 800, 600)
SetupGL()

If ImportStl("SampleMeshAscii.stl") = #False
  MessageRequester("Error", "Failed to import object.")
  End
EndIf

;-MAIN REPEAT
Repeat
  
  Repeat
    Event = WindowEvent()
    
    If Event = #PB_Event_CloseWindow
      Quit = 1
    EndIf
  Until Event = 0
  
  Render()
  
Until Quit = 1
End

;-
;-PROCEDURES
Procedure ImportStl(Path.s)
  
  Define.l Epos
  Define.l File
  Define.l Spos
  
  Define.s Result
  Define.s String
  
  Define.Vector3 Normal
  
  ;Make sure file exists.
  File = ReadFile(#PB_Any, Path)
  If IsFile(File) = 0
    ProcedureReturn #False
  EndIf
  
  ;Begin File Reading
  With Object
    \Handle = 1
    
    While Eof(File) = 0
      Result = LTrim(ReadString(File, #PB_Ascii))
      
      ;Find triangles
      If Mid(Result, 0, 5) = "facet"
        ;Collect triangle's data
        While Eof(File) = 0
          Result = LTrim(ReadString(File, #PB_Ascii))
          
          If Mid(Result, 0, 6) = "vertex"
            ;Found vertex data
            If \VertexCTR + 1 >= \VertexLimit
              \VertexLimit + 1000
              ReDim \Vertex(\VertexLimit)
              ReDim \Normal(\VertexLimit)
            EndIf
            
            \VertexCTR + 1
            
            Spos = 8
            Epos = FindString(Result, " ", Spos)
            String = Mid(Result, Spos, Epos-Spos)
            \Vertex(\VertexCTR)\X = ValF(String)
            Spos = Epos + 1
            
            Epos = FindString(Result, " ", Spos)
            String = Mid(Result, Spos, Epos-Spos)
            \Vertex(\VertexCTR)\Y = ValF(String)
            Spos = Epos + 1
            
            Epos = FindString(Result, " ", Spos)
            String = Mid(Result, Spos)
            \Vertex(\VertexCTR)\Z = ValF(String)
          EndIf
          
          ;Found end of triangle
          If Mid(Result, 0, 8) = "endfacet"
            ;Store Triangle data
            If \TriangleCTR + 1 >= \TriangleLimit
              \TriangleLimit + 1000
              ReDim \Triangle(\TriangleLimit)
            EndIf
            
            \TriangleCTR + 1
            
            \Triangle(\TriangleCTR)\X = \VertexCTR-2
            \Triangle(\TriangleCTR)\Y = \VertexCTR-1
            \Triangle(\TriangleCTR)\Z = \VertexCTR
            
            ;Calculate triangle's normal
            MATH_TriangleNormal(@\Vertex(\VertexCTR-2), @\Vertex(\VertexCTR-1), @\Vertex(\VertexCTR), @Normal)
            \Normal(\VertexCTR-2)\X = Normal\X
            \Normal(\VertexCTR-2)\Y = Normal\Y
            \Normal(\VertexCTR-2)\Z = Normal\Z
            
            \Normal(\VertexCTR-1)\X = Normal\X
            \Normal(\VertexCTR-1)\Y = Normal\Y
            \Normal(\VertexCTR-1)\Z = Normal\Z
            
            \Normal(\VertexCTR)\X   = Normal\X
            \Normal(\VertexCTR)\Y   = Normal\Y
            \Normal(\VertexCTR)\Z   = Normal\Z
            
            Break
          EndIf
        Wend
        
        Continue
      EndIf
    Wend
  EndWith
  
  Debug Object\VertexCTR
  Debug Object\TriangleCTR
  
  ProcedureReturn #True
  
EndProcedure

Procedure Render()
  
  Define.l TriCTR
  Define.l VCTR1, VCTR2, VCTR3
  
  Define.Vector3 Nor1, Nor2, Nor3
  Define.Vector3 Vec1, Vec2, Vec3
  
  SetGadgetAttribute(0, #PB_OpenGL_SetContext, #True)
  
  glPushMatrix_()                  ; Save the original Matrix coordinates
  glMatrixMode_(#GL_MODELVIEW)

  glTranslatef_(0, 0, ZoomFactor)  ;  move the camera out

  glRotatef_(RollAxisX, 1.0, 0, 0) ; rotate around X axis
  glRotatef_(RollAxisY, 0, 1.0, 0) ; rotate around Y axis
  glRotatef_(RollAxisZ, 0, 0, 1.0) ; rotate around Z axis
 
  RollAxisX + RotateSpeedX 
  RollAxisY + RotateSpeedY 
  RollAxisZ + RotateSpeedZ 

  ; clear color and depth buffers
  glClearColor_(0.2, 0.4, 0.6, 1.0)
  glClear_(#GL_COLOR_BUFFER_BIT | #GL_DEPTH_BUFFER_BIT)
  
  With Object
    If \Handle = 1
      glEnable_(#GL_LIGHTING)
      glEnable_(#GL_LIGHT0)
      glBegin_(#GL_TRIANGLES)
      
      For TriCTR = 1 To \TriangleCTR
        VCTR1 = \Triangle(TriCTR)\X
        VCTR2 = \Triangle(TriCTR)\Y
        VCTR3 = \Triangle(TriCTR)\Z
        
        Vec1\X = \Vertex(VCTR1)\X
        Vec1\Y = \Vertex(VCTR1)\Y
        Vec1\Z = \Vertex(VCTR1)\Z
        Nor1\X = \Normal(VCTR1)\X
        Nor1\Y = \Normal(VCTR1)\Y
        Nor1\Z = \Normal(VCTR1)\Z
        
        Vec2\X = \Vertex(VCTR2)\X
        Vec2\Y = \Vertex(VCTR2)\Y
        Vec2\Z = \Vertex(VCTR2)\Z
        Nor2\X = \Normal(VCTR2)\X
        Nor2\Y = \Normal(VCTR2)\Y
        Nor2\Z = \Normal(VCTR2)\Z
        
        Vec3\X = \Vertex(VCTR3)\X
        Vec3\Y = \Vertex(VCTR3)\Y
        Vec3\Z = \Vertex(VCTR3)\Z
        Nor3\X = \Normal(VCTR3)\X
        Nor3\Y = \Normal(VCTR3)\Y
        Nor3\Z = \Normal(VCTR3)\Z
        
        glNormal3f_(Nor1\X, Nor1\Y, Nor1\Z)
        glVertex3f_(Vec1\X, Vec1\Y, Vec1\Z)
        
        glNormal3f_(Nor2\X, Nor2\Y, Nor2\Z)
        glVertex3f_(Vec2\X, Vec2\Y, Vec2\Z)
        
        glNormal3f_(Nor3\X, Nor3\Y, Nor3\Z)
        glVertex3f_(Vec3\X, Vec3\Y, Vec3\Z)
      Next
      glEnd_()
    EndIf
  EndWith

  glPopMatrix_()
  glFinish_()

  SetGadgetAttribute(0, #PB_OpenGL_FlipBuffers, #True)
  
EndProcedure

Procedure SetupGL()
    
  glMatrixMode_(#GL_PROJECTION)
  gluPerspective_(30.0, 800/600, 1.0, 10000.0) 
  
  ; position viewer
  glMatrixMode_(#GL_MODELVIEW)
  
  glTranslatef_(0, 0, -5.0)
  
  glEnable_(#GL_DEPTH_TEST)
  
  glEnable_(#GL_CULL_FACE)
  
  glShadeModel_(#GL_SMOOTH)
  
EndProcedure

;-
;-MATH PROCEDURES
Procedure MATH_Normalize3D(*Value.Vector3)
  
  Define.d Length
  
  Length = Sqr(*Value\X * *Value\X + *Value\Y * *Value\Y + *Value\Z * *Value\Z)
  If Length = 0
    Length = 1
  EndIf
  
  *Value\X = *Value\X / Length
  *Value\Y = *Value\Y / Length
  *Value\Z = *Value\Z / Length

EndProcedure

Procedure MATH_TriangleNormal(*V1.Vector3, *V2.Vector3, *V3.Vector3, *Result.Vector3)
  
  *Result\X = (*V1\Y - *V2\Y) * (*V2\Z - *V3\Z) - (*V1\Z - *V2\Z) * (*V2\Y - *V3\Y)
  *Result\Y = (*V1\Z - *V2\Z) * (*V2\X - *V3\X) - (*V1\X - *V2\X) * (*V2\Z - *V3\Z)
  *Result\Z = (*V1\X - *V2\X) * (*V2\Y - *V3\Y) - (*V1\Y - *V2\Y) * (*V2\X - *V3\X)
  
  MATH_Normalize3D(*Result)
  
EndProcedure

[IdeasVacuum]

Hi Samuel

That does indeed work, good edge definition. It's a totally different approach to the code I was using, glDrawArrays()

[Samuel]

I'd personally recommend sticking with glDrawArrays() or glDrawElements(). Using the old glBegin/glEnd commands are not very efficient for the GPU.
I just used them because it was quicker to write that example.

[applePi]

Thank you Samuel for this nice STL importer, the good normalization makes big difference in the look of the model. as an example now the owl.stl appears like this:

as if it is painted by a metallic spray
Thanks

[IdeasVacuum]

Hi again Samuel

At run time, how can I place a point on the mesh interactively (mouse click) ?