Empty mesh causes SurfaceTools::generate_tangents to fail an assertion which doesn't make sense.

[pl7y]

Tested versions

• Reproducible in 4.2 stable

System information

OSX Sonoma 14.4.1 (23E224)

Issue description

The following error is shown in console:

E 0:00:01:0467   test.gd:22 @ _ready(): Condition "!(format & Mesh::ARRAY_FORMAT_TEX_UV)" is true.
  <C++ Source>   scene/resources/surface_tool.cpp:1151 @ generate_tangents()
  <Stack Trace>  test.gd:22 @ _ready()

If empty meshes are allowed, assertion should not be triggered.
If empty meshes are not allowed, assertion should be checked only if there is some mesh set.

Steps to reproduce

Create a node and add this code to the _ready() function:

func _ready():
  var st = SurfaceTool.new()
  st.begin(Mesh.PRIMITIVE_TRIANGLES)
  st.generate_normals()
  st.generate_tangents()
  var mesh = st.commit()  

Minimal reproduction project (MRP)

See "steps to reproduce".

[AThousandShips]

This fails because you need to have UV to generate tangents as they are related to textures

The error message should be made clearer, but this retirement is clearly documented:

Generates a tangent vector for each vertex. Requires that each vertex have UVs and normals set already (see generate_normals).

[clayjohn]

I agree, the error should be expanded to include a clear message saying that UVs are required to generate tangents.

[Maski0]

(This is my First time Contributing) @clayjohn I would like take up this Issue.
Currently for The Error ERR_FAIL_COND(!(format & Mesh::ARRAY_FORMAT_TEX_UV)); Macro is being
I will be simply using ERR_FAIL_COND_MSG Macro with message saying "UVs are required to generate tangents"
is the above approch good, or is there any better approch. And also if we change the above do i have to change anything else(like documentation)

[clayjohn]

(This is my First time Contributing) @clayjohn I would like take up this Issue. Currently for The Error ERR_FAIL_COND(!(format & Mesh::ARRAY_FORMAT_TEX_UV)); Macro is being I will be simply using ERR_FAIL_COND_MSG Macro with message saying "UVs are required to generate tangents" is the above approch good, or is there any better approch. And also if we change the above do i have to change anything else(like documentation)

Your suggested approach is correct and you don't need to change anything else :)

[Maski0]

Your suggested approach is correct and you don't need to change anything else :)

Ok thank you sir, also a rookie question I am guessing I will have to create a pr for the master itself or for 4.2 branch as the tested version mentioned above.

[clayjohn]

You only need to make a PR for the master branch. We can "cherrypick" the change to the 4.2 branch automatically.