Mfnmesh Initialgroupshading

[pelotoescogorciao]

Hello, i'm new to the forums and Maya API!

I'm finishing a mesh importer translator... but I noticed the mesh I created does not have a default material nor shader assigned.
I've searched a lot on the Internet and forums... but nobody seems to be able to give a clear and specific answer ( with code ).
How can I assign it a material or a initialShadingGroup, please?

Here is my code:

CODE
MFnMesh l_fnMesh;
MObject l_mayaMesh = l_fnMesh.create (lc_iNVerts, lc_iNFaces, l_arrVerts, l_arrNPolys,  l_arrVIndices );

MFnDagNode dagNode ( l_mayaMesh );

The l_arrVerts, l_arrNPolys, l_arrVIndices are filled with the vertices and indices. The mesh is created and visualized well in Maya... but it has no material assigned.
I tried using MGlobal::ExecuteCommand("sets -e -fe initialShadingGroup " ) + l_fnMesh.name() and with a MDGModifier but it does not work ( my plugin is a MPxFileTranslator btw ).

How can I assign, for example, a MFnLambertShader or a MFnPhongShader to the mesh, pls? I would prefer not to call MEL if possible.
I think I need to use a MFnSet and the FnLambershader.create() method ... but I'm a noob and the Maya documentation is not very clear!

thanks.

[joojaa]

QUOTE
I've searched a lot on the Internet and forums... but nobody seems to be able to give a clear and specific answer ( with code ).

thets because theres usually no simple answer.

But yes to help you to think right MFnLambertShader is NOT the shader itself its a accessory object to manipulating the shader, this si a bit unusual about mayas api, so you cant assign it to anything. But yes you can use the MFn t create and manipulate the object you need.

So pseudocode would be.. (too lazy to test code and have nothing to copy paste it from at the moment)

create a new mobject withh your mFNXX type.
create a shading engine node
connect the shaders out color to the newly create shading group
assign objects to the shading group set

QUOTE
MGlobal::ExecuteCommand("sets -e -fe initialShadingGroup " ) + l_fnMesh.name()

chek if l_fnMesh.name() is a valid and unique name. Anyway use MFnSet on initialShadingGroup to add the mobject directly less error prone.

[pelotoescogorciao]

QUOTE(Joojaa @ 12/15/08, 01:19 AM) [snapback]297071[/snapback]
create a new mobject withh your mFNXX type.
create a shading engine node
connect the shaders out color to the newly create shading group
assign objects to the shading group set

Like this?

CODE
//create a new mobject withh your mFNXX type.
MFnMesh l_fnMesh;
MFnMesh l_mayaMesh = l_fnMesh.create (lc_iNVerts, lc_iNFaces, l_arrVerts, l_arrNPolys,  l_arrVIndices );

l_mayaMesh.updateSurface();

MFnDagNode dagNode ( l_mayaMesh );

//create a shading engine node
MfnLambertShader lambert;
MfnLambertShader shader = lambert.create(true);

//connect the shaders out color to the newly create shading group
MPlug pinOut = shader.findPlug("outColor");
MPlug pinIn = l_mayaMesh.findPlug("surfaceColor");
MDGModifier mod;
mod.Connect(pinIn,pinOut);

Ofc, it does not work 8(

[joojaa]

QUOTE(pelotoescog @ 12/15/08, 12:43 PM) [snapback]297081[/snapback]
Like this?

No. See:

QUOTE
//create a shading engine node
MfnLambertShader lambert;
MfnLambertShader shader = lambert.create(true);

You didn't create a shading engine node! you just created a shader. the shader is still MISSING the shading engine node in other words shading group. It still need to be created

So basically you did only the step:

create a new mobject withh your mFNXX type.

Also please read carefully i said "connect the shaders out color to the newly create shading group" NOT the surface or even the dag object. But the shading engine node. Wich if you look carefully you did not do, just the shader.

[pelotoescogorciao]

And how can I create a shading group, pls?
And... why the Maya docs are so poor documented? Is there no quick guide explaining all this stuff? All I see are very complicated and poorly documented examples 8(

[rob-bateman]

QUOTE
And... why the Maya docs are so poor documented?

The Maya docs are extremely well written, and actually provide all of the information you will ever require. There is however one caveat to that - you actually have to read them first. Read the docs for MFnSet, and the node+attr reference for shading engine and you'll have all the information you need.

QUOTE
And how can I create a shading group, pls?

Sorry, but i have to ask. How the hell have you managed to write an importer if you can't figure out how to create a node?

CODE
MFnDependencyNode fn;
MObject oMesh = fn.create("mesh");
MObject oTransform = fn.create("transform");
MObject oEngine = fn.create("shadingEngine");   ///< subtle hint!
MObject oLambert = fn.create("lambert");

QUOTE
Is there no quick guide explaining all this stuff?

Node & Attr reference.

QUOTE
All I see are very complicated and poorly documented examples 8(

Maya is by nature a very complex program, with it's own philosophies. you are not going to find examples that break with those conventions no.

[joojaa]

Well yes but its not self evident that a person has time to read all of the rest for the documentation. mainly because they think api section is self contained.

QUOTE(Rob Bateman @ 12/15/08, 05:32 PM) [snapback]297103[/snapback]
Node & Attr reference.

I want to add one thing here, the node and attr reference contains the information but its often hard to know what node is where. But theres a tool that helps on this or actually 2 tools:

Hypergraph

export selection out as ma file and read what nodes were used in particular scenarios

[pelotoescogorciao]

QUOTE(Rob Bateman @ 12/15/08, 07:32 AM) [snapback]297103[/snapback]
The Maya docs are extremely well written, and actually provide all of the information you will ever require.

Oh well... I require a simple, clear and easy example about how to select a group of faces and then assign a lambert or phong shader...
I'm alone and rounded by lots of foreign words... it's hard to know where to start finding these basic things.

QUOTE
Sorry, but i have to ask. How the hell have you managed to write an importer if you can't figure out how to create a node?

Hey! I'm just learning! I couldn't find the MFnShadingEngine in the docs... that's why I asked how to create a shading engine.
The ::create("shadingEngine") didn't sound very... intuitive. I was expecting a MfnShadingEngine class or A MfnMesh::assignMaterial() method... or something similar.

QUOTE
Well yes but its not self evident that a person has time to read all of the rest for the documentation.

Exactly. On the other hand I would prefer to learn by a concrete, simple and clear code sniplet

[joojaa]

Most of the MFn is a optical illususions of sorts. MFn does not reflect what maya is doing so just reading the api reference will not teach you what maya does. Most MFn's kindof only wraps up the general parts wich may be of special interest. In reality one does not really need much more than only a tiny subset of the MFn mainly because you could in practice do everything with making nodes and accessing their plugs directly, so for example theres really no significant reason for MFnLambert to exist its just a sort of training wheel wrapper around things.

The only way to know for sure is to make maya do it and look at the node graph maya makes. Then mimic that. So you cant learn maya api porgramming by just looking at the maya api, you must know maya.

QUOTE
it's hard to know where to start finding these basic things.

Well no its not you start at the beginning of the maya manual and end up in the api section (well you can skip whats new and tutorials). Truly it is assumed that once you read the api docs you are familiiar with all the other docs. Its kindof important that you know atleast the sections:

• General -> Basics (it teaches you how maya is used and the pihilosphy of its gui, wich lets face it is not the normal gui you often see). Note whole general is important but i cut out the bare bone minimum requirements
• General -> MEL and Expressions
• Animation, Character Setup, and Deformers
• Developer Resources (you can omit reafding all the references but you should skim them trough)

and last but leasta quote highlighted form the manual:

QUOTE
Write file translators
To the Maya ASCII format

If you are writing a program to translate other kinds of files to Maya ASCII file format, the work is fairly straightforward. The bulk of what you need to do is find Maya node and attribute equivalences to the foreign data types. For this you will probably want to construct your own sample Maya files and refer to the document called Node and Attribute Reference.

This holds true even if you do it straight in the api

[pelotoescogorciao]

Thanks, Joojaa. Now I know where to find.

Meanwhile... could anybody provide a small and concrete code sniplet with this simple operations, pls?

1. Assign the initialShading group to an imported mesh
2. Select some random mesh faces and assign a phong shader to them

thx

[rob-bateman]

Whilst i appreciate the maya API can be a bit daunting, you must start to appreciate that you are actually going to have to start reading the documentation to be able to achieve anything in the API. As joojaa has said, you need to cross reference the documentation with what you see in the hypergraph. If you do that, the Maya API becomes a hell of a lot easier.

So i'll start by repeating myself, but all of the required information you need is to be found in the docs for MFnSet, and the node+attr reference for shadingEngine.. Please spend some time reading that documentation - for it contains all of the answers you seek.....

QUOTE
Meanwhile... could anybody provide a small and concrete code sniplet with this simple operations, pls?

What you are asking for is not often going to happen. Maya is huge, and you'll very quickly find that very few people - if any at all - will have ever done what you are attempting. So source examples - barring extremely common cases - are very rare to come by.

I will be nice to you just this once, but please understand that this is not a code example i've have lying around somewhere. It is a piece of code knocked up in the last couple of minutes after having read the documentation.

CODE
MFnMesh fnMesh;
MFnSet fnSet;
MFnTransform fnTransform;

MObject oParent = fnTransform.create();
MObject oMesh = fnMesh.create( /* stuff */, oParent );
MObject oSet = fnSet.create("shadingEngine");
fnSet.addMember(oMesh);

bool toggle=false;

// or add the face seperately....
MItMeshPolygon iter(oMesh);
for(;!iter.isDone();iter.next())
{
  if(toggle)
  {
    fnSet.addMember(oMesh,iter.currentItem());
  }
  toggle = !toggle;
}

MFnPhong fnPhong;
MObject oPhong = fnPhong.create();

MPlug ss = fnSet.findPlug("ss");
MPlug oc = fnPhong.findPlug("outColor");
MDgModifier mod;
mod.connect(oc,ss);
mod.doIt();

[pelotoescogorciao]

Thanks a lot, Rob! That's exactly what I was looking for!
Btw, you should add that piece of code to your excellent Maya tutorials on your web. A lot of people will be thankful!
And yep... now that I know where and what to find, I'll explore deeper the docs.

Thanks!

[pelotoescogorciao]

Just another question related with this:

Why

CODE
MSelectionList selList;
MStatus status = MGlobal::getSelectionListByName( "initialShadingGroup", selList );

the status get a fail? I see that the initialShadingGroup is present even when the Maya scene is empty, so...

[joojaa]

try:

CODE
MSelectionList selList;
MString toMatch ("initialShadingGroup");
MStatus status = selList.add(toMatch );

[pelotoescogorciao]

QUOTE(Joojaa @ 12/17/08, 05:04 AM) [snapback]297242[/snapback]
try:
CODE
MSelectionList selList;
MString toMatch ("initialShadingGroup");
MStatus status = selList.add(toMatch );

fails also

[joojaa]

Seems to work for me. However your doing a importer the secene is not necceserily yet initialized.

[pelotoescogorciao]

QUOTE(Joojaa @ 12/17/08, 06:41 AM) [snapback]297247[/snapback]
Seems to work for me. However your doing a importer the secene is not necceserily yet initialized.

So I bet I can't assume there is a initialShadingGroup created...
Any idea or suggestion about how to assign the default lambert shading group to a mesh without having to create a new one(!=initialShadingGroup), pls?
What I cannot understand is why Maya does not assign a default shading group to the imported meshes by default ( if no shader is specified programatically... )

[joojaa]

Well, there's plenty of valid reasons for not having any shading associated with a mesh (half of all my scenes contain meshes with no shading associated with them). So if you need the overhead of attaching something then do attach it but if not save that time (and not make less work last longer)

But yes they could do this then again its not big deal to make the shading group either. Atfter all its just copy paste form ma file. But the point is if you indtend to do things with a c++ api you should understand its lowlevel if you want higher level representation of maya use mel/python

[pelotoescogorciao]

It seems if I use the MfnDependencyNode.create("shadingEngine") it does not set the renderable attribute 8(
On the other hand the MGlobal::getSelectionListByName("initialShadingGroup") does not work in any way.

The problem is that, for some reason, the mesh is put inside a temporary namespace when the importer is called... so the scene is not initialized, the initialShadingGroup does not exist, MEL commands won't work because the mesh uses a temporal name, etc...
Perhaps I should implement the importer as a MPxCommand and fire it from the MPxTranslator.... XSilo and Maya2Q3 do that it seems...
but looking at Rob's signature I'm not sure this would be a good idea