topic Re: set attribute value in matrix type in Maya Programming Forum

set attribute value in matrix type

egoldid1 — Mon, 13 Nov 2023 18:48:49 GMT

Hello, How I can create a matrix for control position of an object and save it in attributes?

I write this codes but it crashed. i have rotate and translate:

MPlug outMatrixAttrPlug(oThis, outMatrixAttr);

MDataHandle outMatrixHandle = outMatrixAttrPlug.asMDataHandle();

MTransformationMatrix m;

double scale[3] = { 1,1,1 };

m.setScale(scale, MSpace::kTransform);

MEulerRotation rr(MVector(0,45,0), MEulerRotation::RotationOrder::kXYZ);

m.rotateTo(rr);

MVector translate(0, 11, 0);

m.setTranslation(translate, MSpace::kTransform);

outMatrixHandle.setMMatrix(m.asMatrix());

Re: set attribute value in matrix type

jmreinhart — Tue, 14 Nov 2023 18:05:44 GMT

What's the context for this code? Is this code from the ::compute method of a custom node or something like that? If so you should be using the MDataBlock class to get your dataHandles.

Re: set attribute value in matrix type

egoldid1 — Tue, 14 Nov 2023 22:19:34 GMT

hi, yes I wrote it in ::compute method of a custom node.

at first I wrote below code:
outMatrixAttr= matAttr.create("outCCMatrix", "outCCMatrix", MFnMatrixAttribute::kFloat);

when I change MFnMatrixAttribute::kFloat in to MFnMatrixAttribute::kDouble, it now does not crash.

outMatrixAttr = matAttr.create("outCCMatrix", "outCCMatrix", MFnMatrixAttribute::kDouble);

but now in the outMatrixAttr attribute only saving zero values.

Re: set attribute value in matrix type

jmreinhart — Wed, 15 Nov 2023 03:12:17 GMT

Could you please share the full code?

Re: set attribute value in matrix type

egoldid1 — Wed, 15 Nov 2023 13:54:09 GMT

the full code is so long.

-------------

I wrote below code for create attribute:

#...

MFnMatrixAttribute matAttr;

outMatrixAttr = matAttr.create("outCCMatrix", "outCCMatrix", MFnMatrixAttribute::kDouble);

matAttr.setStorable(true);

matAttr.setReadable(true);

matAttr.setKeyable(true);

matAttr.setWritable(false);

matAttr.setHidden(false);

stat = addAttribute(outMatrixAttr );

if (!stat) { stat.perror("addAttribute"); return stat; }

-----------

and in the compute part I wrote below code:

MPlug outMatrixAttrPlug(oThis, outMatrixAttr);

MDataHandle outMatrixHandle = outMatrixAttrPlug.asMDataHandle();

MTransformationMatrix m;
double scale[3] = { 1.0,21.0,1.0 };
m.setScale(scale, MSpace::kTransform);
MEulerRotation rr(MVector(0.0, 20.0, 0.0), MEulerRotation::RotationOrder::kXYZ);
m.rotateTo(rr);
MVector translate(110.0, 11.0, 22.0);
m.setTranslation(translate, MSpace::kTransform);

outMatrixHandle .setMMatrix(m.asMatrix());

and result is zero value:

I am not sure that I can share full code. so much thanks.

Re: set attribute value in matrix type

jmreinhart — Wed, 15 Nov 2023 14:52:26 GMT

I think that you might be misunderstanding how the compute function works. This is a good example to look at https://help.autodesk.com/view/MAYAUL/2022/ENU/?guid=Maya_SDK_Dependency_graph_plug_ins_Implementing_the_compute_method_html

The important bit is this. This is the usual way of getting the dataHandle for a plug during the compute method.

MDataHandle stateData = data.outputValue( state, &status );

I've never used

MPlug().asMDataHandle();

but the documentation says:

Value of plug as an MDataHandle. When done using the returned handle, the caller must destroy it using MPlug::destructHandle().

Hopefully one of those two things will resolve your problem.

Re: set attribute value in matrix type

egoldid1 — Wed, 15 Nov 2023 19:03:17 GMT

thank you. I sued this code and it worked.

MDataHandle outMatrixHandle = data.outputValue(outMatrixAttr);
outMatrixHandle.setMMatrix(m.asMatrix());

Re: set attribute value in matrix type

egoldid1 — Wed, 15 Nov 2023 21:07:52 GMT

now if the outMatrixAttr be child of the outMatrixGRPAttr , how I can write values or how I can use data.outputValue()?

outMatrixGRPAttr = compoundAttr.create("outMatrixGRP", "outMatrixGRP");
compoundAttr.setArray(true);
compoundAttr.setReadable(true);
compoundAttr.setWritable(false);
compoundAttr.setKeyable(true);
compoundAttr.setStorable(true);
compoundAttr.setHidden(false);

outMatrixAttr= matAttr.create("outCCMatrix", "outCCMatrix", MFnMatrixAttribute::kDouble);
matAttr.setStorable(true);
matAttr.setReadable(true);
matAttr.setKeyable(true);
matAttr.setWritable(false);
matAttr.setHidden(false);
compoundAttr.addChild(outMatrixAttr);

stat = addAttribute(outMatrixGRPAttr);
if (!stat) { stat.perror("addAttribute"); return stat; }

Re: set attribute value in matrix type

jmreinhart — Wed, 15 Nov 2023 21:20:49 GMT

It should work the same way. I would recommend clicking on the link and reading about the compute function. Your question is really general, and you'll make more progress referring to the documentation and making an attempt on your own, and posting to the forum if that doesn't work.

Also, small tip if you use the "</>" when making a post that contains code it makes it more readable. Best of luck