Subdivided Cube

[Clyde]

Hiya!

I've made some progress on a subdivided / segmented cube that's made out of the idea of a segmented quad to form the sides. But the texture on the left side doesn't look right. I've compared this with a regular cube, and I believe the u's or v's need rotating 90 degrees to the right.

As far as I know the for loops are fine and don't need dabbling with. I've mucked about with al-sorts of ordering of the u and v positions in the addvertex parts, though not much luck.

Hopefully it's a case of altering the stuff to do with the pos_u0# and pos_v0#.

Code: [Select]

;=================================
; Sub Divided Cube V9.9
; Created By Clyde^GVY 20/05/2012
;=================================
Graphics3D 800,600,32,2
SetBuffer BackBuffer()


Dim textures(2)


Global camera
Global light
Global seg_cube


Global texture_image
Global texture_file$="media\this way up.bmp"


init()
main()




Function init()
   
                   camera=CreateCamera()
   PositionEntity    ( camera, 0.0, 0.0, -10.0 )
   light=CreateLight( camera )
   
   texture_image   =LoadImage      ( texture_file$ )
   textures(0)      =LoadTexture   ( texture_file$ )
   textures(1)      =create_texture   ( 1, 1, $f0f0f0 )
   
   seg_cube      =create_segmented_cube   ( 4, 2, 3, 10.0, 10.0, 10.0 )
   
   PositionEntity   ( seg_cube, 0.0, 0.0, 50.0 )
   EntityTexture   ( seg_cube, textures(0) )


End Function






Function main()


   Local rx#= -45.0
   Local ry#=  45.0
   Local rz#=   0.0
   
   Local wire_mode%=0


   While Not KeyHit(1)
   
      WireFrame( wire_mode% )
   
      EntityTexture( seg_cube, textures( wire_mode% ) )
     
      RotateEntity( seg_cube, rx#, ry#, rz# )
     
      ;==================
      ; a = turn z axis.
      ;==================
      If KeyDown(30) Then rz#=rz#-0.25
     
      ;==================
      ; d = turn z axis.
      ;==================
      If KeyDown(32) Then rz#=rz#+0.25
     
      ;=================
      ; cursor up = up.
      ;=================
      If KeyDown(200) Then rx#=rx#+0.25
     
      ;=====================
      ; cursor down = down.
      ;=====================
      If KeyDown(208) Then rx#=rx#-0.25
     
      ;=====================
      ; cursor left = left.
      ;=====================
      If KeyDown(203) Then ry#=ry#-0.25
     
      ;=======================
      ; cursor right = right.
      ;=======================
      If KeyDown(205) Then ry#=ry#+0.25
     
      ;=======================
      ; w = toggle wireframe.
      ;=======================
      If KeyHit(17) Then wire_mode%=Not wire_mode%
     
      RenderWorld()
     
      DrawImage( texture_image, 0, 0 )
     
      Flip
   Wend


End Function




Function create_segmented_cube( segs_x%, segs_y%, segs_z%, scale_x#, scale_y#, scale_z# )


   Local entity=CreateMesh()
   Local cube   =CreateSurface(entity)
   
   ;=========
   ; floats.
   ;=========
   Local pos_x0#=0.0, pos_y0#=0.0, pos_z0#=0.0
   Local pos_x1#=0.0, pos_y1#=0.0, pos_z1#=0.0
   
   Local pos_u0#=0.0, pos_v0#=0.0
   Local pos_u1#=0.0, pos_v1#=0.0
   
   Local div_u#=0.0
   Local div_v#=0.0
   
   Local xx#=0.0, yy#=0.0, zz#=0.0
   
   Local segs_xx#=Float(segs_x%)
   Local segs_yy#=Float(segs_y%)
   Local segs_zz#=Float(segs_z%)


   ;===========
   ; integers.
   ;===========   
   Local x%=0, y%=0, z%=0
   
   Local v0%=0, v1%=0, v2%=0, v3%=0
   
   ;============
   ; centering.
   ;============
   Local cent_x#=-(( segs_xx# * scale_x# ) / 2.0 )
   Local cent_y#=-(( segs_yy# * scale_y# ) / 2.0 )
   Local cent_z#=-(( segs_zz# * scale_z# ) / 2.0 )
   
   Local left_side%   =1
   Local front_side%   =1
   Local top_side%      =1
   
   ;============
   ; left side.
   ;============
   If ( left_side%=1 ) Then
     
      div_u#= ( 1.0 / segs_yy# )
      div_v#= ( 1.0 / segs_zz# )


      For z%=0 To segs_z%-1
       
           zz#=Float(z%)
       
           For y%=0 To segs_y%-1
       
               yy#=Float(y%)
           
               pos_y0#=cent_y# + ( yy# * scale_y# )
               pos_z0#=cent_z# + ( zz# * scale_z# )
           
               pos_y1#=cent_y# + (( yy# + 1.0 ) * scale_y# )
               pos_z1#=cent_z# + (( zz# + 1.0 ) * scale_z# )


            pos_u0#=div_u# * yy#
            pos_v0#=div_v# * zz#
         
            pos_u1#=div_u# * ( yy# + 1.0 )
            pos_v1#=div_v# * ( zz# + 1.0 )
           
            v0%=AddVertex( cube, cent_x#, -pos_y1#, pos_z0#, -pos_u1#, -pos_v0# )
               v1%=AddVertex( cube, cent_x#, -pos_y0#, pos_z0#, -pos_u0#, -pos_v0# )
           
            v2%=AddVertex( cube, cent_x#, -pos_y0#, pos_z1#, -pos_u0#, -pos_v1# )
               v3%=AddVertex( cube, cent_x#, -pos_y1#, pos_z1#, -pos_u1#, -pos_v1# )


            AddTriangle( cube, v2%, v1%, v0% )
            AddTriangle( cube, v3%, v2%, v0% )
         
         Next
     
       Next
   
   End If
   
   ;============
    ; front side.
    ;============
   If ( front_side%=1 ) Then
   
      div_u#=( 1.0 / segs_xx# )
      div_v#=( 1.0 / segs_yy# )
   
      For y%=0 To segs_y%-1
       
           yy#=Float(y%)
       
           For x%=0 To segs_x%-1
           
               xx#=Float(x%)
           
               pos_x0#=cent_x#+ ( xx#        * scale_x# )
               pos_y0#=cent_y#+ ( yy#        * scale_y# )
           
               pos_x1#=cent_x#+(( xx#+1.0 ) * scale_x# )
               pos_y1#=cent_y#+(( yy#+1.0 ) * scale_y# )
           
               pos_u0#=div_u# * xx#
            pos_v0#=div_v# * yy#
         
            pos_u1#=div_u# * (xx#+1.0)
            pos_v1#=div_v# * (yy#+1.0)
           
               v0=AddVertex( cube, -pos_x0, -pos_y1, cent_z, -pos_u0, pos_v1 )
               v1=AddVertex( cube, -pos_x0, -pos_y0, cent_z, -pos_u0, pos_v0 )
               v2=AddVertex( cube, -pos_x1, -pos_y0, cent_z, -pos_u1, pos_v0 )
               v3=AddVertex( cube, -pos_x1, -pos_y1, cent_z, -pos_u1, pos_v1 )
         
            AddTriangle( cube, v2%, v1%, v0% )
            AddTriangle( cube, v3%, v2%, v0% )
         
         Next
      Next
   
   End If
   
   ;===========
    ; top side.
    ;===========
   If ( top_side%=1 ) Then


      div_u#=( 1.0 / segs_xx# )
      div_v#=( 1.0 / segs_zz# )


      For z%=0 To segs_z%-1
       
           zz#=Float(z%)
       
           For x%=0 To segs_x%-1
           
               xx#=Float(x%)
           
               pos_x0#=cent_x#+(  xx#        * scale_x# )
               pos_z0#=cent_z#+(  zz#        * scale_z# )
           
               pos_x1#=cent_x#+(( xx#+1.0 ) * scale_x# )
               pos_z1#=cent_z#+(( zz#+1.0 ) * scale_z# )
           
                pos_u0#=div_u# * xx#
            pos_v0#=div_v# * zz#
         
            pos_u1#=div_u# * (xx#+1.0)
            pos_v1#=div_v# * (zz#+1.0)




               v0%=AddVertex( cube, pos_x1#, -cent_y#, pos_z0#, pos_u1#, -pos_v0# )
               v1%=AddVertex( cube, pos_x0#, -cent_y#, pos_z0#, pos_u0#, -pos_v0# )
               v2%=AddVertex( cube, pos_x0#, -cent_y#, pos_z1#, pos_u0#, -pos_v1# )
               v3%=AddVertex( cube, pos_x1#, -cent_y#, pos_z1#, pos_u1#, -pos_v1# )
           
              AddTriangle( cube, v0%, v1%, v2% )
            AddTriangle( cube, v0%, v2%, v3% )


           Next
       Next
   End If
   
   UpdateNormals( entity )
   Return        ( entity )
   
End Function




Function create_texture( wwidth%, height%, colour% )
   
   Local x%=0, y%=0
   
   Local texture=CreateTexture( wwidth%, height% )


   SetBuffer       TextureBuffer( texture )
   LockBuffer       TextureBuffer( texture )
   
   For y%=0 To height%-1
      For x%=0 To wwidth%-1
         WritePixelFast( x%,y%, colour%, TextureBuffer( texture ) )
      Next
   Next
   
   UnlockBuffer    TextureBuffer( texture )
   SetBuffer       BackBuffer()


   Return texture


End Function

I know I've used b3d to illustrate the problem, but I shall be converting this over into a different language once sussed, so please no inbuilt b3d commands.

Cheers For The Help - Much Appreciated!!!
Clyde.

[Jim]

If you just use 8 vertices and 8 uvs and try to link them up it can't work. Try using 4 vertices per face.
Jim

[Hotshot]

So simple looking 3D Cube on Small code of Blitz 3D as show how simple it is 

[Clyde]

I don't quite follow. Surely if I use less verts, I'll have missing adjacent triangles?

I also need to do my own rotate verts routine ( rather than the built in blitz command ) as I hope to use this in another lingo, but not sure on doing that. And it will make creating the segmented quads / subdivided cube easier.

Thanks in advance.

[Jim]

You need more vertices, not less.  A cube has 8 corners and you can join these up using triangles to make all the faces.  What you can't do with only 8 vertices is get the uvs right on all faces at the same time.  Some will be jumbled up and I thought this was probably your problem.
To get the uvs right, you need 4 vertices per cube face, i.e. 24 vertices.  Each corner then has 3 vertices at exactly the same location, but now they have the possibility of having distinct uv coordinates.

Jim

[hellfire]

I think he's already generating an NxM grid for each side of the cube.
And the problem is the orientation of the grids (which is easy to fix with a bit of effort).
Just had a rough look over the code, though, so I can be totally wrong...

[Clyde]

I think that sounds promising & thanks.
Is any part of if near to what you'd usually do for this type of object?

I'd really love a hand or two in pulling this off!!

Cheers and respect,
Clyde.

[hellfire]

Just to get it right, you're trying to create this kind of thing?

[hellfire]

You can only get the uvs for four neighbouring sides right.
The top and bottom face can't match, no matter how you rotate them.