How Do I Add a Blend Shape to a Mesh Array?

[ewoud]

Godot Version

Godot 4.5

Question

In my project I’m making great use of ArrayMeshes. But now I want to use blendshapes, however, I don’t understand how they are supposed to be used. And I cannot really find examples of them online.

Below is a snippet where I try to morph a square to a triangle using Blend Shapes, you can find the full example here.

func generate():
	var square_mesh := square_array()
	var triangle_mesh := triangle_array()

	var a_mesh := ArrayMesh.new()
	a_mesh.add_blend_shape("Triangle Shape")
	a_mesh.add_surface_from_arrays(Mesh.PRIMITIVE_TRIANGLES, square_mesh, [triangle_mesh])
	mesh = a_mesh

However, this results in this error:

ERROR: Blend shape format must match the main array format for Vertex, Normal and Tangent arrays.
ERROR: scene/resources/mesh.cpp:1825 - Condition “err != OK” is true.

[normalized]

Why [triangle_mesh] when triangle_mesh is already properly formatted array?

[ewoud]

Because it’s expecting an array of MeshArrays, check out the docs.

What happens if you use the already properly formatted array? You get a different error:

ERROR: Unable to convert array index 2 from “Nil” to “Array”.
ERROR: scene/resources/mesh.cpp:1819 - Condition “p_blend_shapes.size() != blend_shapes.size()” is true.

[normalized]

Try adding the tangents array in both.

[ewoud]

Tried that too, you can find my attempt here. I’m not too familiar with how tangents work, but it spits out the same error again:

ERROR: Blend shape format must match the main array format for Vertex, Normal and Tangent arrays.
ERROR: scene/resources/mesh.cpp:1825 - Condition “err != OK” is true.

[normalized]

Tangents should be a vector3 array

[ewoud]

According to the docs that I am reading, it’s a PackedFloat32Array.

[normalized]

Have you tried with a non-indexed mesh?

[ewoud]

Hey now it’s working! Simply removing the indices from the blend shape mesh made it work. Thanks!