diff --git a/Project.toml b/Project.toml
index 88dee08..eff6939 100644
--- a/Project.toml
+++ b/Project.toml
@@ -7,11 +7,13 @@ version = "1.1.0"
 ColorSchemes = "35d6a980-a343-548e-a6ea-1d62b119f2f4"
 Colors = "5ae59095-9a9b-59fe-a467-6f913c188581"
 DocStringExtensions = "ffbed154-4ef7-542d-bbb7-c09d3a79fcae"
+GeometryBasics = "5c1252a2-5f33-56bf-86c9-59e7332b4326"
 StaticArraysCore = "1e83bf80-4336-4d27-bf5d-d5a4f845583c"
 
 [compat]
 ColorSchemes = "3"
 Colors = "0.12"
 DocStringExtensions = "0.8, 0.9"
+GeometryBasics = "0.4"
 StaticArraysCore = "1.4"
 julia = "1.6"
diff --git a/src/GridVisualizeTools.jl b/src/GridVisualizeTools.jl
index ac91403..d95dc73 100644
--- a/src/GridVisualizeTools.jl
+++ b/src/GridVisualizeTools.jl
@@ -5,6 +5,7 @@ import ColorSchemes
 
 using DocStringExtensions: SIGNATURES, TYPEDEF, TYPEDSIGNATURES
 using StaticArraysCore: SVector
+using GeometryBasics: Point
 
 include("colors.jl")
 export region_cmap, bregion_cmap, rgbtuple
@@ -12,9 +13,16 @@ export region_cmap, bregion_cmap, rgbtuple
 include("extraction.jl")
 export extract_visible_cells3D, extract_visible_bfaces3D
 
+include("linearsimplex.jl")
+export LinearSimplex, LinearSimplexIterator
+export LinearEdge, LinearTriangle, LinearTetrahedron
+export testloop
+
 include("marching.jl")
+include("marching_iterators.jl")
 export marching_tetrahedra, marching_triangles
 
+
 include("markerpoints.jl")
 export markerpoints
 
diff --git a/src/linearsimplex.jl b/src/linearsimplex.jl
new file mode 100644
index 0000000..d533972
--- /dev/null
+++ b/src/linearsimplex.jl
@@ -0,0 +1,95 @@
+struct LinearSimplex{D,N,Tv}
+    points::SVector{N,Point{D,Tv}}
+    values::SVector{N,Tv}
+end
+
+values(s::LinearSimplex)=s.values
+points(s::LinearSimplex)=s.points
+
+
+function LinearSimplex(::Type{Val{D}},points::Union{Vector,Tuple}, values::Union{Vector,Tuple}) where {D}
+    spoints=SVector{D+1,Point{D,Float32}}(points...)
+    svalues=SVector{D+1,Float32}(values...)
+    LinearSimplex(spoints,svalues)
+end
+
+function LinearSimplex(::Type{Val{1}},points::AbstractMatrix, values::AbstractVector)
+    @views spoints=SVector{2,Point{1,Float32}}(points[:,1],points[:,2])
+    svalues=SVector{2,Float32}(values[1],values[2])
+    LinearSimplex(spoints,svalues)
+end
+
+function LinearSimplex(::Type{Val{2}},points::AbstractMatrix, values::AbstractVector)
+    @views spoints=SVector{3,Point{2,Float32}}(points[:,1],points[:,2],points[:,3])
+    svalues=SVector{3,Float32}(values[1],values[2],values[3])
+    LinearSimplex(spoints,svalues)
+end
+
+function LinearSimplex(::Type{Val{3}},points::AbstractMatrix, values::AbstractVector)
+    @views spoints=SVector{4,Point{3,Float32}}(points[:,1],points[:,2],points[:,3],points[:,4])
+    svalues=SVector{4,Float32}(values[1],values[2],values[3],values[4])
+    LinearSimplex(spoints,svalues)
+end
+
+
+function LinearSimplex(::Type{Val{1}},points::AbstractMatrix, values::AbstractVector,coordscale)
+    @views spoints=SVector{2,Point{1,Float32}}(points[:,1]*coordscale,points[:,2]*coordscale)
+    svalues=SVector{2,Float32}(values[1],values[2])
+    LinearSimplex(spoints,svalues)
+end
+
+function LinearSimplex(::Type{Val{2}},points::AbstractMatrix, values::AbstractVector,coordscale)
+    @views spoints=SVector{3,Point{2,Float32}}(points[:,1]*coordscale,points[:,2]*coordscale,points[:,3]*coordscale)
+    svalues=SVector{3,Float32}(values[1],values[2],values[3])
+    LinearSimplex(spoints,svalues)
+end
+
+function LinearSimplex(::Type{Val{3}},points::AbstractMatrix, values::AbstractVector,coordscale)
+    @views spoints=SVector{4,Point{3,Float32}}(points[:,1]*coordscale,points[:,2]*coordscale,points[:,3]*coordscale,points[:,4]*coordscale)
+    svalues=SVector{4,Float32}(values[1],values[2],values[3],values[4])
+    LinearSimplex(spoints,svalues)
+end
+
+LinearEdge(points,values)=LinearSimplex(Val{1},points,values)
+LinearTriangle(points,values)=LinearSimplex(Val{2},points,values)
+LinearTetrahedron(points,values)=LinearSimplex(Val{3},points,values)
+
+
+"""
+    abstract type LinearSimplexIterator{D}
+
+Iterator over D-dimensional linear simplices. 
+
+Any subtype `TSub` should comply with the [iteration interface](https://docs.julialang.org/en/v1/manual/interfaces/#man-interface-iteration)
+and implement
+```julia
+     Base.iterate(vs::TSub{D}, state):: (LinearSimplex{D}, state) where D
+```
+The optional methods (in particular, size, length) are not needed.
+"""
+abstract type LinearSimplexIterator{D} end
+
+"""
+    testloop(iterators::AbstractVector{T}) where T<:LinearSimplexIterator
+
+Sum up all values passed via the iterator. Designed for testing iterators.
+
+Useful for:
+- Consistency test - e.g. when passing constant ones, the sum can be calculated by 
+  other means and compared to the return value of testloop
+- Allocation test. `testloop` itself does allocate only a few (<1000) bytes in
+  very few (<10) allocations. So any allocations beyond this from a
+  call to `testloop` hint at possibilities to improve an iterator implementation.
+"""
+function testloop(iterators::AbstractVector{T}) where T<:LinearSimplexIterator
+    threads=map(iterators) do iterator 
+	begin
+	    local x=0.0
+            for vt in iterator
+            	x+=sum(vt.values)
+            end
+	    x
+	end	 
+    end
+    sum(fetch.(threads))
+end
diff --git a/src/marching_iterators.jl b/src/marching_iterators.jl
new file mode 100644
index 0000000..1a85305
--- /dev/null
+++ b/src/marching_iterators.jl
@@ -0,0 +1,63 @@
+function pushintersection!(intersection_points,triangle::LinearSimplex{2},levels)
+    f = values(triangle)
+    coord=points(triangle)
+    
+    (n1, n2, n3) = (1, 2, 3)
+    
+    f[1] <= f[2] ? (n1, n2) = (1, 2) : (n1, n2) = (2, 1)
+    f[n2] <= f[3] ? n3 = 3 : (n2, n3) = (3, n2)
+    f[n1] > f[n2] ? (n1, n2) = (n2, n1) : nothing
+    
+    dx31 = coord[n3][1] - coord[n1][1]
+    dx21 = coord[n2][1] - coord[n1][1]
+    dx32 = coord[n3][1] - coord[n2][1]
+    
+    dy31 = coord[n3][2] - coord[n1][2]
+    dy21 = coord[n2][2] - coord[n1][2]
+    dy32 = coord[n3][2] - coord[n2][2]
+    
+    df31 = f[n3] != f[n1] ? 1 / (f[n3] - f[n1]) : 0.0
+    df21 = f[n2] != f[n1] ? 1 / (f[n2] - f[n1]) : 0.0
+    df32 = f[n3] != f[n2] ? 1 / (f[n3] - f[n2]) : 0.0
+    
+    for level ∈ levels
+        if (f[n1] <= level) && (level < f[n3])
+            α = (level - f[n1]) * df31
+            x1 = coord[n1][1] + α * dx31
+            y1 = coord[n1][2] + α * dy31
+            
+            if (level < f[n2])
+                α = (level - f[n1]) * df21
+                x2 = coord[n1][1] + α * dx21
+                y2 = coord[n1][2] + α * dy21
+            else
+                α = (level - f[n2]) * df32
+                x2 = coord[n2][1] + α * dx32
+                y2 = coord[n2][2] + α * dy32
+            end
+            push!(intersection_points, Point{2,Float32}(x1, y1))
+            push!(intersection_points, Point{2,Float32}(x2, y2))
+        end
+    end
+end
+
+function intersections(triangles::T,levels) where T<:LinearSimplexIterator{2}
+    local intersection_points = Vector{Point{2,Float32}}(undef, 0)
+    for triangle in triangles
+        pushintersection!(intersection_points,triangle,levels)
+    end
+    intersection_points
+end
+
+function marching_triangles(triangle_iterators::Vector{T},levels) where T<:LinearSimplexIterator{2}
+    if Threads.nthreads()==1
+        map(triangle_iterators) do triangles
+            intersections(triangles,levels)
+        end
+    else
+        threads=map(triangle_iterators) do triangles
+            Threads.@spawn intersections(triangles,levels)
+        end
+        fetch.(threads)
+    end
+end