How to access/fiddle with Mesh resource?

slephy

Hi everyone,

I'm looking to fiddle with the Mesh resource but I can't seem to figure out how to access its property and play with its methods. I understand MeshInstance is how you talk to MeshInstance nodes, but I have no idea how to access resources.

Can anyone point me in the right direction? Thanks!!

TwistedTwigleg

I have not used it myself, but I think the MeshDataTool lets you mess around with existing mesh resources. The documentation has a page on using the MeshDataTool that may be worth a look.

slephy

@TwistedTwigleg said: I have not used it myself, but I think the MeshDataTool lets you mess around with existing mesh resources. The documentation has a page on using the MeshDataTool that may be worth a look.

Hey thank you! This is rather what I was looking for, a way to access and modify the vertex data. I'll definitely fiddle with this! :)

On a side note though....I still don't understand how to play with resources. lol. Does anyone have any idea where to start?

TwistedTwigleg

@slephy said:

@TwistedTwigleg said: I have not used it myself, but I think the MeshDataTool lets you mess around with existing mesh resources. The documentation has a page on using the MeshDataTool that may be worth a look.

Hey thank you! This is rather what I was looking for, a way to access and modify the vertex data. I'll definitely fiddle with this! :)

Great! :smile:

On a side note though....I still don't understand how to play with resources. lol. Does anyone have any idea where to start?

I think it depends on the resource in question. Some resources expose data for manipulation, but others do not. The class reference for the Mesh resource shows there is unfortunately not really anything exposed for data manipulation, just converting the Mesh resource to other resources. You can get the surface data, but there does not appear to be any way to set the surface data from the Mesh resource itself. They ArrayMesh resource looks like it offers some data manipulation capabilities though.

slephy

Ah I see, I see. So it looks like accessing some of those resources is done by creating a new version of that resource? (I'm probably not using the proper language because in other documentation it says a resource has only one copy stored of it so loading it once is enough)...but something like:

var arr_mesh = ArrayMesh.new()

...would be a way to access and begin to modify resources

slephy

I figured out how to access the "Mesh" class as a resource!

If you're scripting inside of a MeshInstance node (by using "extends MeshInstance"), then you can of course directly reference MeshInstance's "mesh" property, which returns a "Mesh" value. (Note the difference in lowercase and capital... "mesh" as a property, "Mesh" as a class)

so for instance:

var this_mesh = mesh

"this_mesh" is now stores a "Mesh" value (printing it for me returns [CubeMesh:1187] for my particular mesh)

and since Mesh has its own property, "lightmap_size_hint", and methods, "get_aabb()" for instance, you can then print:

print( this_mesh.lightmap_size_hint )

print( this_mesh.get_aabb() )

if you don't want to first store the "Mesh" value returned from "mesh" property, you could just go straight ahead and do

print( mesh.get_aabb() )

...which prints the AABB from the "Mesh" class

Hope that helps anyone who comes across this post!

slephy

I'm beginning to play with the MeshDataTool and if, like me, you're having trouble using the MeshDataTool's create_from_surface(...), I have some info!

A MeshInstance whose shape is defined with a PrimitiveMesh (see the MeshInstances' Inspector>>Mesh drop down menu), won't satisfy the MeshDataTool's create_from_surface(...) argument

create_from_surface(...) takes an ArrayMesh as an argument, not a PrimitiveMesh (such as CubeMesh, CylinderMesh, etc, and all the PrimitiveMeshes ) .

So, instead of using a PrimitiveMesh, looks like one must first either create an ArrayMesh or import a mesh from Blender, since an imported mesh is also constructed using the ArrayMesh class.

The debug error I was getting over and over was "E 0:00:01.067 create_from_surface: Condition "p_mesh.is_null()" is true. Returned: ERR_INVALID_PARAMETER" in case anyone else is banging their head against the wall.

A lot of this is resolved in this excellent youtube video on mesh manipulation, where he discusses encountering the same initial problem I was facing and how he resolved it: Godot - 3D Mesh Manipulation - 01 - Introduction to using C# with the Rider IDE It's in C# but I had no problem following it as a GDScript user.

Hope that helps anyone on a similar path!

woopdeedoo

Yes, for dealing with meshes through code you'll need an ArrayMesh. You don't necessarily need the MeshDataTool though, but I suppose this depends on what you want to achieve. I haven't used it much, so I'm not sure what it's actually intended for.

I used a mesh, for example, for creating a grid for a map editor (which I never was able to get done), and in that case I just fed the meshes directly with arrays of vertices and colors. Basically it's just a bunch of colored lines stored in three meshes (and performs better than ImmediateGeometry). You can also provide it with arrays of UV coordinates, normals, indices, etc.

Indices allow you to reuse vertices (e.g. a cube can be made out of 8 vertices, instead of 36 (for 12 triangles)), but I only know how to use them in very basic ways. If you need some more (basic) info on indices, I made a (perhaps needlessly over-extensive) answer about it here.

PS: that series of videos helped me a bunch too. :) That and looking at Godot's source code, since the 3D gizmos are also made using meshes.