assimp/code/SkeletonMeshBuilder.cpp

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Open Asset Import Library (assimp)
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/** @file  SkeletonMeshBuilder.cpp
 *  @brief Implementation of a little class to construct a dummy mesh for a skeleton 
 */

#include "AssimpPCH.h"
#include "../include/assimp/scene.h"
#include "SkeletonMeshBuilder.h"

using namespace Assimp;

// ------------------------------------------------------------------------------------------------
// The constructor processes the given scene and adds a mesh there. 
SkeletonMeshBuilder::SkeletonMeshBuilder( aiScene* pScene, aiNode* root, bool bKnobsOnly)
{
	// nothing to do if there's mesh data already present at the scene
	if( pScene->mNumMeshes > 0 || pScene->mRootNode == NULL)
		return;

	if (!root)
		root = pScene->mRootNode;

	mKnobsOnly = bKnobsOnly;

	// build some faces around each node 
	CreateGeometry( root );

	// create a mesh to hold all the generated faces
	pScene->mNumMeshes = 1;
	pScene->mMeshes = new aiMesh*[1];
	pScene->mMeshes[0] = CreateMesh();
	// and install it at the root node
	root->mNumMeshes = 1;
	root->mMeshes = new unsigned int[1];
	root->mMeshes[0] = 0;

	// create a dummy material for the mesh
	pScene->mNumMaterials = 1;
	pScene->mMaterials = new aiMaterial*[1];
	pScene->mMaterials[0] = CreateMaterial();
}

// ------------------------------------------------------------------------------------------------
// Recursively builds a simple mesh representation for the given node 
void SkeletonMeshBuilder::CreateGeometry( const aiNode* pNode)
{
	// add a joint entry for the node. 
	const unsigned int vertexStartIndex = mVertices.size();

	// now build the geometry. 
	if( pNode->mNumChildren > 0 && !mKnobsOnly)
	{
		// If the node has children, we build little pointers to each of them
		for( unsigned int a = 0; a < pNode->mNumChildren; a++)
		{
			// find a suitable coordinate system
			const aiMatrix4x4& childTransform = pNode->mChildren[a]->mTransformation;
			aiVector3D childpos( childTransform.a4, childTransform.b4, childTransform.c4);
			float distanceToChild = childpos.Length();
			if( distanceToChild < 0.0001f)
				continue;
			aiVector3D up = aiVector3D( childpos).Normalize();

			aiVector3D orth( 1.0f, 0.0f, 0.0f);
			if( fabs( orth * up) > 0.99f)
				orth.Set( 0.0f, 1.0f, 0.0f);

			aiVector3D front = (up ^ orth).Normalize();
			aiVector3D side = (front ^ up).Normalize();

			unsigned int localVertexStart = mVertices.size();
			mVertices.push_back( -front * distanceToChild * 0.1f);
			mVertices.push_back( childpos);
			mVertices.push_back( -side * distanceToChild * 0.1f);
			mVertices.push_back( -side * distanceToChild * 0.1f);
			mVertices.push_back( childpos);
			mVertices.push_back( front * distanceToChild * 0.1f);
			mVertices.push_back( front * distanceToChild * 0.1f);
			mVertices.push_back( childpos);
			mVertices.push_back( side * distanceToChild * 0.1f);
			mVertices.push_back( side * distanceToChild * 0.1f);
			mVertices.push_back( childpos);
			mVertices.push_back( -front * distanceToChild * 0.1f);

			mFaces.push_back( Face( localVertexStart + 0, localVertexStart + 1, localVertexStart + 2));
			mFaces.push_back( Face( localVertexStart + 3, localVertexStart + 4, localVertexStart + 5));
			mFaces.push_back( Face( localVertexStart + 6, localVertexStart + 7, localVertexStart + 8));
			mFaces.push_back( Face( localVertexStart + 9, localVertexStart + 10, localVertexStart + 11));
		}
	} 
	else
	{
		// if the node has no children, it's an end node. Put a little knob there instead
		aiVector3D ownpos( pNode->mTransformation.a4, pNode->mTransformation.b4, pNode->mTransformation.c4);
		float sizeEstimate = ownpos.Length() * 0.18f;

		mVertices.push_back( aiVector3D( -sizeEstimate, 0.0f, 0.0f));
		mVertices.push_back( aiVector3D( 0.0f, sizeEstimate, 0.0f));
		mVertices.push_back( aiVector3D( 0.0f, 0.0f, -sizeEstimate));
		mVertices.push_back( aiVector3D( 0.0f, sizeEstimate, 0.0f));
		mVertices.push_back( aiVector3D( sizeEstimate, 0.0f, 0.0f));
		mVertices.push_back( aiVector3D( 0.0f, 0.0f, -sizeEstimate));
		mVertices.push_back( aiVector3D( sizeEstimate, 0.0f, 0.0f));
		mVertices.push_back( aiVector3D( 0.0f, -sizeEstimate, 0.0f));
		mVertices.push_back( aiVector3D( 0.0f, 0.0f, -sizeEstimate));
		mVertices.push_back( aiVector3D( 0.0f, -sizeEstimate, 0.0f));
		mVertices.push_back( aiVector3D( -sizeEstimate, 0.0f, 0.0f));
		mVertices.push_back( aiVector3D( 0.0f, 0.0f, -sizeEstimate));

		mVertices.push_back( aiVector3D( -sizeEstimate, 0.0f, 0.0f));
		mVertices.push_back( aiVector3D( 0.0f, 0.0f, sizeEstimate));
		mVertices.push_back( aiVector3D( 0.0f, sizeEstimate, 0.0f));
		mVertices.push_back( aiVector3D( 0.0f, sizeEstimate, 0.0f));
		mVertices.push_back( aiVector3D( 0.0f, 0.0f, sizeEstimate));
		mVertices.push_back( aiVector3D( sizeEstimate, 0.0f, 0.0f));
		mVertices.push_back( aiVector3D( sizeEstimate, 0.0f, 0.0f));
		mVertices.push_back( aiVector3D( 0.0f, 0.0f, sizeEstimate));
		mVertices.push_back( aiVector3D( 0.0f, -sizeEstimate, 0.0f));
		mVertices.push_back( aiVector3D( 0.0f, -sizeEstimate, 0.0f));
		mVertices.push_back( aiVector3D( 0.0f, 0.0f, sizeEstimate));
		mVertices.push_back( aiVector3D( -sizeEstimate, 0.0f, 0.0f));

		mFaces.push_back( Face( vertexStartIndex + 0, vertexStartIndex + 1, vertexStartIndex + 2));
		mFaces.push_back( Face( vertexStartIndex + 3, vertexStartIndex + 4, vertexStartIndex + 5));
		mFaces.push_back( Face( vertexStartIndex + 6, vertexStartIndex + 7, vertexStartIndex + 8));
		mFaces.push_back( Face( vertexStartIndex + 9, vertexStartIndex + 10, vertexStartIndex + 11));
		mFaces.push_back( Face( vertexStartIndex + 12, vertexStartIndex + 13, vertexStartIndex + 14));
		mFaces.push_back( Face( vertexStartIndex + 15, vertexStartIndex + 16, vertexStartIndex + 17));
		mFaces.push_back( Face( vertexStartIndex + 18, vertexStartIndex + 19, vertexStartIndex + 20));
		mFaces.push_back( Face( vertexStartIndex + 21, vertexStartIndex + 22, vertexStartIndex + 23));
	}

	unsigned int numVertices = mVertices.size() - vertexStartIndex;
	if( numVertices > 0)
	{
		// create a bone affecting all the newly created vertices
		aiBone* bone = new aiBone;
		mBones.push_back( bone);
		bone->mName = pNode->mName;

		// calculate the bone offset matrix by concatenating the inverse transformations of all parents
		bone->mOffsetMatrix = aiMatrix4x4( pNode->mTransformation).Inverse();
		for( aiNode* parent = pNode->mParent; parent != NULL; parent = parent->mParent)
			bone->mOffsetMatrix = aiMatrix4x4( parent->mTransformation).Inverse() * bone->mOffsetMatrix;

		// add all the vertices to the bone's influences
		bone->mNumWeights = numVertices;
		bone->mWeights = new aiVertexWeight[numVertices];
		for( unsigned int a = 0; a < numVertices; a++)
			bone->mWeights[a] = aiVertexWeight( vertexStartIndex + a, 1.0f);

		// HACK: (thom) transform all vertices to the bone's local space. Should be done before adding
		// them to the array, but I'm tired now and I'm annoyed.
		aiMatrix4x4 boneToMeshTransform = aiMatrix4x4( bone->mOffsetMatrix).Inverse();
		for( unsigned int a = vertexStartIndex; a < mVertices.size(); a++)
			mVertices[a] = boneToMeshTransform * mVertices[a];
	}

	// and finally recurse into the children list
	for( unsigned int a = 0; a < pNode->mNumChildren; a++)
		CreateGeometry( pNode->mChildren[a]);
}

// ------------------------------------------------------------------------------------------------
// Creates the mesh from the internally accumulated stuff and returns it.
aiMesh* SkeletonMeshBuilder::CreateMesh()
{
	aiMesh* mesh = new aiMesh();

	// add points
	mesh->mNumVertices = mVertices.size();
	mesh->mVertices = new aiVector3D[mesh->mNumVertices];
	std::copy( mVertices.begin(), mVertices.end(), mesh->mVertices);

	mesh->mNormals = new aiVector3D[mesh->mNumVertices];

	// add faces
	mesh->mNumFaces = mFaces.size();
	mesh->mFaces = new aiFace[mesh->mNumFaces];
	for( unsigned int a = 0; a < mesh->mNumFaces; a++)
	{
		const Face& inface = mFaces[a];
		aiFace& outface = mesh->mFaces[a];
		outface.mNumIndices = 3;
		outface.mIndices = new unsigned int[3];
		outface.mIndices[0] = inface.mIndices[0];
		outface.mIndices[1] = inface.mIndices[1];
		outface.mIndices[2] = inface.mIndices[2];

		// Compute per-face normals ... we don't want the bones to be smoothed ... they're built to visualize
		// the skeleton, so it's good if there's a visual difference to the rest of the geometry
		aiVector3D nor = ((mVertices[inface.mIndices[2]] - mVertices[inface.mIndices[0]]) ^ 
			(mVertices[inface.mIndices[1]] - mVertices[inface.mIndices[0]]));

		if (nor.Length() < 1e-5f) /* ensure that FindInvalidData won't remove us ...*/
			nor = aiVector3D(1.f,0.f,0.f);

		for (unsigned int n = 0; n < 3; ++n)
			mesh->mNormals[inface.mIndices[n]] = nor;
	}

	// add the bones
	mesh->mNumBones = mBones.size();
	mesh->mBones = new aiBone*[mesh->mNumBones];
	std::copy( mBones.begin(), mBones.end(), mesh->mBones);

	// default
	mesh->mMaterialIndex = 0;

	return mesh;
}

// ------------------------------------------------------------------------------------------------
// Creates a dummy material and returns it.
aiMaterial* SkeletonMeshBuilder::CreateMaterial()
{
	aiMaterial* matHelper = new aiMaterial;

	// Name
	aiString matName( std::string( "SkeletonMaterial"));
	matHelper->AddProperty( &matName, AI_MATKEY_NAME);

	// Prevent backface culling
	const int no_cull = 1;
	matHelper->AddProperty(&no_cull,1,AI_MATKEY_TWOSIDED);

	return matHelper;
}