simple fbx creation / export

[flugi]

Hello, I would like to ask what do I wrong. My goal is to reproduce an FBX file exported from Unreal in FBX format, it looks like this in ASSXML:

<?xml version="1.0" encoding="utf-8"?>
<ASSIMP format_id="1">

<!-- XML Model dump produced by assimp dump
  Library version: 5.1.1784941101
  Source: fromUe01.assxml
  Command line: 
  Thu Jan 13 16:40:46 2022

--> 

<Scene flags="1" postprocessing="0">
<Node name="RootNode"> 
        <Matrix4> 
                 1.000000  0.000000  0.000000  0.000000
                 0.000000  1.000000  0.000000  0.000000
                 0.000000  0.000000  1.000000  0.000000
                 0.000000  0.000000  0.000000  1.000000
        </Matrix4> 
        <NodeList num="1">
                <Node name="Transform"> 
                        <Matrix4> 
                                 1.000000  0.000000  0.000000  0.000000
                                 0.000000  1.000000  0.000000  0.000000
                                 0.000000  0.000000  1.000000  0.000000
                                 0.000000  0.000000  0.000000  1.000000
                        </Matrix4> 
                </Node>
        </NodeList>
</Node>
<AnimationList num="1">
        <Animation name="Unreal Take" duration="1.970000e+02" tick_cnt="3.000000e+01">
                <NodeAnimList num="1">
                        <NodeAnim node="Transform">
                                <PositionKeyList num="6">
                                        <PositionKey time="0.000000e+00">
                                                 75.859131  23.375469  141.611603
                                        </PositionKey>
                                        <PositionKey time="1.000000e+00">
                                                 75.975891  23.503031  141.917999
                                        </PositionKey>
                                        <PositionKey time="2.000000e+00">
                                                 76.053589  23.599880  142.232193
                                        </PositionKey>
                                        <PositionKey time="3.000000e+00">
                                                 76.133949  23.694901  142.548706
                                        </PositionKey>
                                        <PositionKey time="4.000000e+00">
                                                 76.351929  23.783800  142.797699
                                        </PositionKey>
                                        <PositionKey time="1.970000e+02">
                                                 74.607674  26.636080  164.361298
                                        </PositionKey>
                                </PositionKeyList>
                                <ScalingKeyList num="6">
                                        <ScalingKey time="0.000000e+00">
                                                 1.000000  1.000000  1.000000
                                        </ScalingKey>
                                        <ScalingKey time="1.000000e+00">
                                                 1.000000  1.000000  1.000000
                                        </ScalingKey>
                                        <ScalingKey time="2.000000e+00">
                                                 1.000000  1.000000  1.000000
                                        </ScalingKey>
                                        <ScalingKey time="3.000000e+00">
                                                 1.000000  1.000000  1.000000
                                        </ScalingKey>
                                        <ScalingKey time="4.000000e+00">
                                                 1.000000  1.000000  1.000000
                                        </ScalingKey>
                                        <ScalingKey time="1.970000e+02">
                                                 1.000000  1.000000  1.000000
                                        </ScalingKey>
                                </ScalingKeyList>
                                <RotationKeyList num="6">
                                        <RotationKey time="0.000000e+00">
                                                 0.000000  0.000000  0.000000  1.000000
                                        </RotationKey>
                                        <RotationKey time="1.000000e+00">
                                                 0.000000  0.000000  0.000000  1.000000
                                        </RotationKey>
                                        <RotationKey time="2.000000e+00">
                                                 0.000000  0.000000  0.000000  1.000000
                                        </RotationKey>
                                        <RotationKey time="3.000000e+00">
                                                 0.000000  0.000000  0.000000  1.000000
                                        </RotationKey>
                                        <RotationKey time="4.000000e+00">
                                                 0.000000  0.000000  0.000000  1.000000
                                        </RotationKey>
                                        <RotationKey time="1.970000e+02">
                                                 0.000000  0.000000  0.000000  1.000000
                                        </RotationKey>
                                </RotationKeyList>
                        </NodeAnim>
                </NodeAnimList>
        </Animation>
</AnimationList>
</Scene>

So I tried to mimic this structure with the following code:

#include <iostream>
#include <vector>
#include <assimp/scene.h>
#include <assimp/anim.h>
#include <assimp/Exporter.hpp>

using namespace std;
using namespace Assimp;

int main() {
	aiScene * scene = new aiScene;
	scene->mRootNode = new aiNode();
	aiAnimation * anim = new aiAnimation; 
	anim->mDuration = 10;
	scene->mAnimations = &anim;
	scene->mNumAnimations = 1;
	
	aiNode * trnode = new aiNode("Transform");
	trnode->mTransformation = aiMatrix4x4();
	scene->mRootNode->addChildren(1,&trnode);
	
	aiNodeAnim * nodeanim = new aiNodeAnim;
	nodeanim->mNodeName = "Transform";
	vector<aiVectorKey *> vec;
	vector<aiVectorKey *> svec;
	vector<aiQuatKey *> qvec;

	for (int i=0;i<10;i++) {
		aiVectorKey * newkey = new aiVectorKey;
		aiQuatKey * qkey = new aiQuatKey;
		aiVectorKey * skey = new aiVectorKey;
		
		newkey -> mTime = i;
		newkey -> mValue = aiVector3D(i,0,0);;
		
		qkey ->mTime = i;
		qkey ->mValue = aiQuaternion(0,0,0);

		skey -> mTime = i;
		skey -> mValue = aiVector3D(1.0,1.0,1.0);
		
		
		vec.push_back(newkey);
		qvec.push_back(qkey);
		svec.push_back(skey);
	}
	aiVectorKey * ptr = (vec[0]);
	nodeanim->mPositionKeys = ptr;

	aiQuatKey * qptr = (qvec[0]);
	nodeanim->mRotationKeys = qptr;

	aiVectorKey * sptr = (svec[0]);
	nodeanim->mScalingKeys = sptr;

	nodeanim->mNumPositionKeys = 10;
	nodeanim->mNumRotationKeys = 10;
	nodeanim->mNumScalingKeys = 10;
	
	std::cout <<"HasAnimations:" << scene->HasAnimations() << std::endl;
	
	Exporter exp;
	exp.Export(scene, "fbx", "test.fbx");
}

but the output is only the root node despite it prints a "1" for the question HasAnimations() :

<?xml version="1.0" encoding="utf-8"?>
<ASSIMP format_id="1">

<!-- XML Model dump produced by assimp dump
  Library version: 5.1.1784941101
  Source: test.assxml
  Command line: 
  Thu Jan 20 16:21:06 2022

--> 

<Scene flags="1" postprocessing="0">
<Node name="RootNode"> 
        <Matrix4> 
                 1.000000  0.000000  0.000000  0.000000
                 0.000000  1.000000  0.000000  0.000000
                 0.000000  0.000000  1.000000  0.000000
                 0.000000  0.000000  0.000000  1.000000
        </Matrix4> 
        <NodeList num="1">
                <Node name="Transform"> 
                        <Matrix4> 
                                 1.000000  0.000000  0.000000  0.000000
                                 0.000000  1.000000  0.000000  0.000000
                                 0.000000  0.000000  1.000000  0.000000
                                 0.000000  0.000000  0.000000  1.000000
                        </Matrix4> 
                </Node>
        </NodeList>
</Node>
</Scene>
</ASSIMP>

[kimkulling]

First thing I saw: the number of animation keys for transformations, rotations and scaling are 10 in your example, but 6 in the xml-file. And the nodeanim-instances are not connected to your model. You need to add the to a NodeAnim and add them to the aiScene instance.

Then you will be able to see it in your exported XML-File.

[flugi]

Thanks for the help!

The first xml is the dump of the desired content which I want to mimic in format, so the length is not interesting, I don't want to reproduce the content but the format only.

I tried to connect the nodeanim instance, you are right it was missing, but adding the following right before the export part:

    anim->mChannels = &nodeanim;
    anim->mName = "anim";
    anim->mNumChannels = 1;
    anim->mTicksPerSecond = 30;

did not solve the issue.

[flugi]

I finally found a solution, the ** meaning was different than I assumed, no need for array of pointers, instead of that you may have multiple plain arrays of pod.

My bad!