Texturing a mesh

Hi Folks,

A nice simple question, I suspect.

I've created a shape - in this case an elongated cube - from scratch, ie, AddVertex, AddTriangle, etc, and I want to texture it with a basic wall like texture(possibly a different texture on top of the wall?). Can someone show me the sequence of commands needed to do this? I have no problem with primitives but my own meshes are causing me problems.

I suspect this has to do with UVs, right?

Anyway help much appreciated.

Later,

Jes

You set the UV when you create the vertex.

A U or V co-ord goes from 0 to 1. Zero being the left hand side or top and 1 being the right hand side or bottom depending on if you're dealing with the U or V respectivly.

Hi Folks,

Thanks Rob, but that's not helped much. I understand what you've said but that still hasn't helped me put the texture onto my slab.

Later,

Jes

Well, if you've got your UV's set correctly, you just need to:

tex = LoadTexture("wall_texture.bmp") ;or whatever name it is.
EntityTexture my_mesh,tex

Or am I missing something? :)

You need to decide how you want your texture to wrap around your mesh before you assign the U,V coordinates.

For example, if you only want the 'front' side of the cube to be textured, then you could just assign the 'front' vertices values of
0,0
0,1
1,0
and 1,1.
All other vertices could just remain at 0,0. Then you could apply a texture with an image that is basically square and only the 'front' of the cube would be covered.


But if you wanted to texture every side of the cube with a different image then you would have to assign the vertices U,V coordinates something like:
.333,0 .666,0
0,.25 .333,.25 .666,.25 1,.25
0,.5 .333,.5 .666,.5 1,.5
.333,.75 .666,.75
.333,1 .666,1
and then create a texture with an image that is arranged something like an unfolded box

.1.
234
.5.
.6.

The 1,2,3,4,5,6 represent the different parts of your image that will cover different sides of the cube. The . represent empty areas of the image.
(sorry this couldn't be more clear without images)

Note that this is just one way to do it.

Edit: Putting more thought into this, I realize that the example I showed above actually would use more than 4 vertices. It would require 14 vertices.

I'm sure it can be done using only 4 vertices but maybe this will give you an idea how to go about it.

Hi Folks,

Ok, think I've got it, I'll give it a go.

Later,

Jes

Hi Folks,

Ok, here is the code I'm using at the moment. This builds a cube using vertices and triangles and then applies a texture to it. Simple so far. However, the texture goes well odd across different parts of the faces.

Graphics3D 800,600

Type Systems_Type
	Field cam, cx#, cy#, cz#, cp
	Field lgt, lx#, ly#, lz# 
End Type
Global sys.systems_type

Type entities_Type
	Field brsh
	Field br,bg,bb
	Field ent, ex#, ey#, ez#
	Field surf
	Field er,eg,eb
	Field tex
End Type
Global ent.entities_type
	
; Set up system stuff
sys.systems_type = New systems_type
sys\cam = CreateCamera()
sys\cx = 20 : sys\cy = 30 : sys\cz = 5

sys\lgt = CreateLight(1)
sys\lx = 10 : sys\ly = 40 : sys\cz = 10

AmbientLight 255,255,255

; set up entities 
Ent.entities_type = New entities_type
ent\brsh = CreateBrush()
ent\br = 255 : ent\bg = 0 : ent\bb = 0
BrushColor ent\brsh,ent\br, ent\bg, ent\bb
ent\Ent = CreateMesh()
ent\Surf = CreateSurface(ent\ent, ent\brsh)
ent\tex = LoadTexture("twistedlandscape.bmp")

Restore CubeData
Read num_verts

For i = 1 To num_verts
	Read vx#,vy#,vz#, vu#, vv#
	AddVertex ent\surf, vx,vy,vz, vu, vv
Next

Read num_tris

For i = 1 To num_tris
	Read v1#,v2#,v3#
	AddTriangle ent\surf, v1,v2,v3
Next

UpdateNormals ent\ent

EntityTexture ent\ent, ent\tex
ScaleEntity ent\ent,10,10,10
EntityShininess ent\ent,.75

PositionEntity ent\ent,ent\ex, ent\ey, ent\ez

PositionEntity sys\lgt,sys\lx, sys\ly, sys\lz

;WireFrame True
SetBuffer BackBuffer()

While Not KeyDown(1)
	sys\cp = sys\cp - 1 : If sys\cp<0 Then sys\cp = 359
	Movecamera
	UpdateWorld
	RenderWorld
	Flip
Wend

End

Function MoveCamera()
sys\cx = 20*Sin(sys\cp)
sys\cz = 20*Cos(sys\cp)

PositionEntity sys\cam,sys\cx,sys\cy, sys\cz
PointEntity sys\cam, ent\ent
End Function

.CubeData
; Number of Vertices = 8
Data 8
; Front
Data 0,1,0,0,1 ; 0
Data 1,1,0,1,1  ; 1
Data 1,0,0,1,0 ; 2
Data 0,0,0,0,0; 3
; Back
Data 1,1,1,1,1   ; 4
Data 0,1,1,0,1  ; 5
Data 0,0,1,0,0 ; 6
Data 1,0,1,0,1  ; 7

; Number of Triangles
Data 10
Data 0,1,2 ; Front
Data 0,2,3

Data 4,5,6 ; Back
Data 4,6,7

Data 5,0,3 ; Left
Data 5,3,6

Data 1,4,7 ; Right
Data 1,7,2

Data 5,4,1 ; Top
Data 5,1,0

Whoops, premature posting ;0)

So, the question is, do I have to create multiple vertices at the same location to correctly map the texture to? I don't think that very likely but...? How else can I map the texture presented(a square texture) on each face?

Thanks,

Jes

No need to create multiple verts, you share verts across a face normally.

Just consider each face a flat plane, as that's all it is. And each vert has a uv range of 0 to 1. (Think of this as a percentage of the texture's width/height)

e.g, u=0.5,v=0.5 = Centre of texture.

Now for each face, considering it's just a flat plane, just consider it on a whole, rather than a series of polys.

So for the front face. Two triangles.

Top Left corner(On tri 1) would be 0,0. Top Right Corner(Shared between tri 1 and 2) would be 1,0

Bottom left corner(Shared by tri 1 and 2) would be 0,1

And finally bottom right corner(tri 2) would be 1,1

Now just repeat the same uvs for each face, because they're just flat planes and rotation doesn't affect texture mapping. It can warp it in blitz, in some cases if you're not using even surfaces though.

Also if you want to scale a texture down so it appears smaller yet still tiles across the surface, still use the 0,1 range, and use TextureScale with a number within 0 to 1. and it'll tile it across the face.

Hi Folks,

Yep, I've got that, thanks. The problem are those faces that share verts, so for example, the front face is going to share it's top left vertex with the bottom left vertex of the top face. Where the vertices don't 'clash' like that it's no problem, only where there are multiple faces. Am I making sense or talking baps?

As an example, a di. I have facing me number 3, the top face is number 1. The top left vertex is going to be the top left of the 3 image and at the same time is going to be the bottom left of the 1 image. Does that help or are my baps floured but undercooked?

Later,

Jes

Hi Folks,

Can anyone help me with this?

Later,

Jes