Drawing solid 3D uvw textures

[danlooo]

Hello,

The texture of a mesh can be expressed as a 3D solid. For example, the OBJ file format allows having uvw coordinates besides of 2D uv ones. This is useful e.g. in complex meshes having a surface that can't be easily wrapped to a 2D texture uv plane.

Providing the texture as a Vector works. Seems that if I use a Matrix, the w coordinate is ignored. Using a 3D array results in an eror. Do I need to flatten a uvw texture into a vector with element order matching to those in msh.uv of mesh msh ?

using MeshIO, Downloads, FileIO, GLMakie

file = Downloads.download("https://raw.githubusercontent.com/JuliaIO/MeshIO.jl/master/test/testfiles/cube_uvw.obj", "shape.obj")
msh = load(file)

mesh(msh; color=1:8) # Vector works
mesh(msh; color=reshape(1:9, (3,3))) # Matrix works
mesh(msh; color=reshape(1:8, (2,2,2)))

The last command results in error

Error showing value of type Makie.FigureAxisPlot:
ERROR: MethodError: no method matching GLMakie.GLAbstraction.GLBuffer(::Array{Float32, 3})

Closest candidates are:
  GLMakie.GLAbstraction.GLBuffer(::Type{T}, ::Int64; buffertype, usage) where T<:Union{Real, ColorTypes.Colorant, StaticArraysCore.StaticArray{Tuple{N}, T, 1} where {N, T}}
   @ GLMakie ~/.julia/packages/GLMakie/yNddL/src/GLAbstraction/GLBuffer.jl:93
  GLMakie.GLAbstraction.GLBuffer(::GLMakie.GLAbstraction.GLBuffer)
   @ GLMakie ~/.julia/packages/GLMakie/yNddL/src/GLAbstraction/GLBuffer.jl:76
  GLMakie.GLAbstraction.GLBuffer(::DenseVector{T}; buffertype, usage) where T<:Union{Real, ColorTypes.Colorant, StaticArraysCore.StaticArray{Tuple{N}, T, 1} where {N, T}}
   @ GLMakie ~/.julia/packages/GLMakie/yNddL/src/GLAbstraction/GLBuffer.jl:52
  ...

with Mesh

julia> msh.uv
8-element Vector{Vec{3, Float32}}:
 [0.0, 0.0, 0.0]
 [1.0, 0.0, 0.0]
 [0.0, 1.0, 0.0]
 [0.0, 0.0, 1.0]
 [1.0, 1.0, 0.0]
 [0.0, 1.0, 1.0]
 [1.0, 0.0, 1.0]
 [1.0, 1.0, 1.0]

[SimonDanisch]

I started this PR to support 3d arrays, but run out of time for tests + clean up:
#2274

[danlooo]

@SimonDanisch thanks very much :) I'll look at the code and see if I can add some tests...

[danlooo]

I could not find any other uvw examples besides the cube above I created manually. Seems thats uvw is not very popular. Mostly used to store pre-computed shading. If we set vt to just the positions v, we have a identity uvw map for sanity checks of the shader code:

mtllib cube.mtl
o Cube
v 1.000000 -1.000000 -1.000000
v 1.000000 -1.000000 1.000000
v -1.000000 -1.000000 1.000000
v -1.000000 -1.000000 -1.000000
v 1.000000 1.000000 -0.999999
v 0.999999 1.000000 1.000001
v -1.000000 1.000000 1.000000
v -1.000000 1.000000 -1.000000

vt 1.000000 -1.000000 -1.000000
vt 1.000000 -1.000000 1.000000
vt -1.000000 -1.000000 1.000000
vt -1.000000 -1.000000 -1.000000
vt 1.000000 1.000000 -0.999999
vt 0.999999 1.000000 1.000001
vt -1.000000 1.000000 1.000000
vt -1.000000 1.000000 -1.000000

usemtl Material
s off
f 1 2 3 4
f 5 8 7 6
f 1 5 6 2
f 2 6 7 3
f 3 7 8 4
f 5 1 4 8

[ffreyer]

Can this be closed?

[asinghvi17]

Mostly - the mesh uv interpolation seems to work, but I'm not sure how the uv coordinates relate to the data that's passed in. A volume plot seems to indicate something fishy is going on...will post a youtube link in a bit.

[asinghvi17]

https://www.youtube.com/watch?v=P5JS9daJZsc