Fix projection from clip to data space (#3909)

* Fix undefined variable in `project` when passing a `Scene`

See https://github.com/HolyLab/FlyThroughPaths.jl/actions/runs/9246991707/job/25435166970?pr=6#step:8:45 for the original error message.

* Add tests to make sure all projections work

* Add changelog

---------

Co-authored-by: Frederic Freyer <frederic481994@hotmail.de>

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## [Unreleased]
 
+- Correct a bug in the `project` function when projecting using a `Scene`. [#3909](https://github.com/MakieOrg/Makie.jl/pull/3909).
+
 ## [0.21.5] - 2024-07-07
 
 - Fixed tuple argument for `WGLMakie.activate!(resize_to=(:parent, nothing))` [#4009](https://github.com/MakieOrg/Makie.jl/pull/4009).

src/camera/projection_math.jl

@@ -401,7 +401,7 @@ function project(scenelike::SceneLike, input_space::Symbol, output_space::Symbol
     output_from_clip = clip_to_space(cam, output_space)
     output_f32c = inv_f32_convert_matrix(scenelike, output_space)
 
-    p4d = to_ndim(Point4{T}, to_ndim(Point3{T}, transformed, 0), 1)
+    p4d = to_ndim(Point4{T}, to_ndim(Point3{T}, pos, 0), 1)
     transformed = output_f32c * output_from_clip * clip_from_input * input_f32c * p4d
     return Point3{T}(transformed[Vec(1, 2, 3)] ./ transformed[4])
 end

test/projection_math.jl

@@ -1,4 +1,33 @@
+using Makie
+
 @testset "Projection math" begin
-    @test eltype(Makie.rotationmatrix_x(1)) == Float64
-    @test eltype(Makie.rotationmatrix_x(1f0)) == Float32
+    @testset "Rotation matrix" begin
+        @test eltype(Makie.rotationmatrix_x(1)) == Float64
+        @test eltype(Makie.rotationmatrix_x(1f0)) == Float32
+    end
+    @testset "Projection between spaces in 3D" begin
+        # Set up an LScene and some points there
+        sc = Scene(size = (650, 400), camera = cam3d!)
+        corner_points_px = [Point3f(0, 0, 0), Point3f(650, 400, 0)]
+
+        @testset "Clip space and pixel space equivalence" begin
+            far_bottom_left_clip = Point3f(-1)
+            near_top_right_clip = Point3f(1)
+
+            fbl_px = Makie.project(sc, :clip, :pixel, far_bottom_left_clip)
+            ntr_px = Makie.project(sc, :clip, :pixel, near_top_right_clip)
+            @test Point2f(fbl_px) == Point2f(0, 0)
+            @test Point2f(ntr_px) == Point2f(650, 400)
+        end
+
+        @testset "No warnings in projections between spaces" begin
+            for (source, dest) in unique(Iterators.product(Makie.spaces(), Makie.spaces()))
+                source == dest && continue
+                current_space_points = Makie.project.(sc, :pixel, source, corner_points_px)
+                @testset "$source → $dest" begin
+                    @test_nowarn Makie.project.(sc, source, dest, current_space_points)
+                end
+            end
+        end
+    end
 end