Part Modding: Error: SubPartTemplate is null for ''

[Spaceman3d]

When I try to laod my Part Mod, KSA crashes and I get the following Error:

Preparing Part Thumbnails...
System.NullReferenceException: SubPartTemplate is null for ''
at KSA.ModLibrary.Get[T](String id)
at KSA.SubPartReference.GetTemplate()
at KSA.SubPart..ctor(SubPartReference inReference, Part inParent)
at KSA.Part..ctor(PartTemplate inTemplate, Vehicle inVehicle, String inName)
at KSA.Rendering.ThumbnailEditor.PreparePartThumbnails(Loading inLoader, Viewport inRenderedViewport)
at KSA.Program.PreparePartThumbnails(Loading loader)
at KSA.Program..ctor(IReadOnlyList`1 inArgs)
at KSA.Program.Main(String[] inArgs) .ctor (in C:\prototype-planet\KSA\Program.cs:300)

 

[Casellina X]

I haven't done any part modding, I've just been looking through the code. Does the XML for you part contain the Id attribute for the subpart? From ../Content/Core/PartAssets.xml line 845 (I went deeper for something maybe more representative?):

    <SubPart Id="ApolloCSMDetailsSubPart">
        <SubPartModel Id="ApolloCSMDetailsSubPartModel">
            <Mesh Id="ApolloCSMDetails"/>
            <Material Id="Apollo2Mat"/>
        </SubPartModel>

        <Engine Id="AJ10-137">
            <Location X="-6.5" Y="0.0" Z="0.0" />
            <ExhaustDirection X="-1" Y="0" Z="0" />
            <!-- Realistic values -->
            <!-- <Thrust KN="43.7" /> -->
            <!-- <SpecificImpulse Seconds="319" /> -->
            <!-- <MinimumThrottle Value="1" /> -->
            <Thrust KN="650" />
            <SpecificImpulse Seconds="100000" />
            <MinimumThrottle Value="0.05" />
            <VolumetricExhaust Id="ApolloCSM" />
            <SoundEvent Action="On" SoundId="DefaultEngineSoundBehavior"/>
        </Engine>
    </SubPart>

And the decompiled code for ModLibary:

        if (typeFromHandle == typeof(SubPartTemplate) || typeFromHandle.IsSubclassOf(typeof(SubPartTemplate)))
        {
            if (!(AllSubParts.Find(KeyHash.Make(id)) is T result9) || 1 == 0)
            {
                throw new NullReferenceException(typeFromHandle.Name + " is null for '" + id + "'");
            }

            return result9;
        }

This may be the cause.

 

[Spaceman3d]

I have the id attribute but is still brings up the same Error

<Assets>

  <MeshFile Id="MCRN TachiMeshFile" Path="Meshes/MCRN_Tachi.glb" Category="Vessel" />
 
  <PbrMaterial Id="TachiMat">
        <Diffuse Path="Textures/Tachi_DIffuse.png" Category="Vessel"/>
        <Normal Path="Textures/Tachi_Normal.png" Category="Vessel"/>
        <RoughMetalAo Path="Textures/Tachi_ORM.png" Category="Vessel"/>
    </PbrMaterial>

  <Part Id="MCRN-Tachi">
    <SubPart Id="MCRN Tachi">
        <SubPartModel Id="MCRN_TachiModel">
            <Mesh Id="MCRN TachiMeshFile"/>
            <Material Id="TachiMat"/>
        </SubPartModel>     
    </SubPart>
    
  </Part>

</Assets>

 

[UriahGnu]

Hi, so here's the change that caused this, and the fix:

Revision 2859

• Separated references to SubParts from their definitions. This helps prevent duplicate definitions and allows us to give each SubPart instance its own ID separate from the template ID.
• Moved all inline-defined SubParts out into their own definitions.

Previously you could define a SubPart Id inside a Part, but now you must instead define it byself and then use SubPart InstanceOf inside the part like below, hope that helps.

    <SubPart Id="Axis_SubPart">
        <SubPartModel Id="Axis_SubPartModel">
            <Mesh Id="Axis_Mesh"/>
            <Material Id="RGB_Test_Mat"/>
        </SubPartModel>
    </SubPart>

    <Part Id="Axis_Part">
        <SubPart InstanceOf="Axis_SubPart"/>
        <Connector>
            <Transform>
                <Position X="0.0"/>
            </Transform>
        </Connector>
    </Part>

 

[Spaceman3d]

So I copyed your code above and replaced all file paths with my model file paths and now get this Error:

System.NullReferenceException: Object reference not set to an instance of an object.
at KSA.SubPartModel..ctor(SubPartModelReference inModelReference)
at KSA.SubPartModel.Get(SubPartModelReference inModelReference)
at KSA.SubPart..ctor(String inName, SubPartTemplate inTemplate, Part inParent, Nullable`1 inTransform, Nullable`1 inGimbal)
at KSA.SubPart..ctor(SubPartReference inReference, Part inParent)
at KSA.Part..ctor(PartTemplate inTemplate, Vehicle inVehicle, String inName)
at KSA.Rendering.ThumbnailEditor.PreparePartThumbnails(Loading inLoader, Viewport inRenderedViewport)
at KSA.Program.PreparePartThumbnails(Loading loader)
at KSA.Program..ctor(IReadOnlyList`1 inArgs)
at KSA.Program.Main(String[] inArgs) .ctor (in C:\prototype-planet\KSA\Program.cs:300)

Code:

<Assets>
    <MeshFile Id="MCRN-Tachi_Mesh" Path="Meshes/MCRN_Tachi.glb" Category="Vessel"/>
    
    <PbrMaterial Id="MCRN-Tachi_Mat">
        <Diffuse Path="Textures/Tachi_DIffuse.png" Category="Vessel"/>
        <Normal Path="Textures/Tachi_Normal.png" Category="Vessel"/>
        <RoughMetalAo Path="Textures/Tachi_ORM.png" Category="Vessel"/>
    </PbrMaterial>

    <SubPart Id="MCRN-Tachi_SubPart">
        <SubPartModel Id="MCRN-Tachi_SubPartModel">
            <Mesh Id="MCRN-Tachi_Mesh"/>
            <Material Id="MCRN-Tachi_Mat"/>
        </SubPartModel>
    </SubPart>

    <Part Id="MCRN-Tachi_Part">
        <SubPart InstanceOf="MCRN-Tachi_SubPart"/>
        <Connector>
            <Transform>
                <Position X="0.0"/>
            </Transform>
        </Connector>
    </Part>
</Assets>

 

[UriahGnu]

Yeah sorry not sure what your issue is. That should be correct. KSA is very sensitive to naming, is this your only SubPart in the entire mod?

 

[Casellina X]

I guess my Software Engineering problem-solving skills need yet more work. I tried following your latest stack trace in v2025.11.11.2924 and I'm at a loss. Your XML looks fine - you give it everything it's asking for.

Could it maybe a typo in your Diffuse path? :
<Diffuse Path="Textures/Tachi_DIffuse.png" Category="Vessel"/>
vs
<Diffuse Path="Textures/Tachi_Diffuse.png" Category="Vessel"/>

 

[UriahGnu]

Nice catch, upper case I in DIffuse.

 

[Spaceman3d]

Welp same Errot still. I checked the typo was also in the texture file name,as I copied the texture file name. wold not have made a diffrence bur tried annyway
only subpart

 

[UriahGnu]

Upload your files

 

[Spaceman3d]

Here is the file. meshes and textures included. Its just a part without anny RCS or engines. Also I havent created a Vehicle. My idea is to use the Editor to place it into the world and the use the "Create new Vehicle button" to make it a seperate vehicle

 

[UriahGnu]

Your problem is <RoughMetalAo> they switched to the more standard ORM format, which is now <AoRoughMetal>, I know, I know

Also, you have some duplicate IDs in your mod that will conflict with Core, including the following, you'll want to remove/rename these.

ApolloRCS
ApolloCSM
EngineA
MmuRcsVac

Hope that helps!

 

[Spaceman3d]

updated the ORM texture and removed the "exhaustAssets.xml" file. still crashes same error. Attached Updated the Mod file

 

[UriahGnu]

Your material still says <RoughMetalAo>, it should be <AoRoughMetal>

 

[Spaceman3d]

IT'S WORKING!!!!!!!!! Thanks for the Help. great Comunity here!