531 lines
19 KiB
C++
531 lines
19 KiB
C++
/*
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---------------------------------------------------------------------------
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Open Asset Import Library (assimp)
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---------------------------------------------------------------------------
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Copyright (c) 2006-2019, assimp team
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All rights reserved.
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Redistribution and use of this software in source and binary forms,
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with or without modification, are permitted provided that the following
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conditions are met:
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* Redistributions of source code must retain the above
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copyright notice, this list of conditions and the
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following disclaimer.
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* Redistributions in binary form must reproduce the above
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copyright notice, this list of conditions and the
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following disclaimer in the documentation and/or other
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materials provided with the distribution.
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* Neither the name of the assimp team, nor the names of its
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contributors may be used to endorse or promote products
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derived from this software without specific prior
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written permission of the assimp team.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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---------------------------------------------------------------------------
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*/
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/** @file TriangulateProcess.cpp
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* @brief Implementation of the post processing step to split up
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* all faces with more than three indices into triangles.
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*
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*
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* The triangulation algorithm will handle concave or convex polygons.
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* Self-intersecting or non-planar polygons are not rejected, but
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* they're probably not triangulated correctly.
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*
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* DEBUG SWITCHES - do not enable any of them in release builds:
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*
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* AI_BUILD_TRIANGULATE_COLOR_FACE_WINDING
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* - generates vertex colors to represent the face winding order.
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* the first vertex of a polygon becomes red, the last blue.
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* AI_BUILD_TRIANGULATE_DEBUG_POLYS
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* - dump all polygons and their triangulation sequences to
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* a file
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*/
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#ifndef ASSIMP_BUILD_NO_TRIANGULATE_PROCESS
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#include "TriangulateProcess.h"
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#include "ProcessHelper.h"
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#include "PolyTools.h"
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#include <memory>
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//#define AI_BUILD_TRIANGULATE_COLOR_FACE_WINDING
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//#define AI_BUILD_TRIANGULATE_DEBUG_POLYS
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#define POLY_GRID_Y 40
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#define POLY_GRID_X 70
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#define POLY_GRID_XPAD 20
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#define POLY_OUTPUT_FILE "assimp_polygons_debug.txt"
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using namespace Assimp;
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// ------------------------------------------------------------------------------------------------
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// Constructor to be privately used by Importer
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TriangulateProcess::TriangulateProcess()
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{
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// nothing to do here
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}
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// ------------------------------------------------------------------------------------------------
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// Destructor, private as well
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TriangulateProcess::~TriangulateProcess()
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{
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// nothing to do here
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}
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// ------------------------------------------------------------------------------------------------
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// Returns whether the processing step is present in the given flag field.
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bool TriangulateProcess::IsActive( unsigned int pFlags) const
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{
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return (pFlags & aiProcess_Triangulate) != 0;
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}
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// ------------------------------------------------------------------------------------------------
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// Executes the post processing step on the given imported data.
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void TriangulateProcess::Execute( aiScene* pScene)
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{
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ASSIMP_LOG_DEBUG("TriangulateProcess begin");
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bool bHas = false;
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for( unsigned int a = 0; a < pScene->mNumMeshes; a++)
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{
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if (pScene->mMeshes[ a ]) {
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if ( TriangulateMesh( pScene->mMeshes[ a ] ) ) {
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bHas = true;
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}
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}
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}
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if ( bHas ) {
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ASSIMP_LOG_INFO( "TriangulateProcess finished. All polygons have been triangulated." );
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} else {
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ASSIMP_LOG_DEBUG( "TriangulateProcess finished. There was nothing to be done." );
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}
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}
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// ------------------------------------------------------------------------------------------------
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// Triangulates the given mesh.
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bool TriangulateProcess::TriangulateMesh( aiMesh* pMesh)
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{
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// Now we have aiMesh::mPrimitiveTypes, so this is only here for test cases
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if (!pMesh->mPrimitiveTypes) {
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bool bNeed = false;
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for( unsigned int a = 0; a < pMesh->mNumFaces; a++) {
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const aiFace& face = pMesh->mFaces[a];
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if( face.mNumIndices != 3) {
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bNeed = true;
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}
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}
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if (!bNeed)
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return false;
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}
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else if (!(pMesh->mPrimitiveTypes & aiPrimitiveType_POLYGON)) {
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return false;
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}
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// Find out how many output faces we'll get
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unsigned int numOut = 0, max_out = 0;
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bool get_normals = true;
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for( unsigned int a = 0; a < pMesh->mNumFaces; a++) {
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aiFace& face = pMesh->mFaces[a];
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if (face.mNumIndices <= 4) {
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get_normals = false;
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}
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if( face.mNumIndices <= 3) {
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numOut++;
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}
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else {
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numOut += face.mNumIndices-2;
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max_out = std::max(max_out,face.mNumIndices);
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}
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}
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// Just another check whether aiMesh::mPrimitiveTypes is correct
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ai_assert(numOut != pMesh->mNumFaces);
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aiVector3D* nor_out = NULL;
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// if we don't have normals yet, but expect them to be a cheap side
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// product of triangulation anyway, allocate storage for them.
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if (!pMesh->mNormals && get_normals) {
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// XXX need a mechanism to inform the GenVertexNormals process to treat these normals as preprocessed per-face normals
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// nor_out = pMesh->mNormals = new aiVector3D[pMesh->mNumVertices];
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}
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// the output mesh will contain triangles, but no polys anymore
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pMesh->mPrimitiveTypes |= aiPrimitiveType_TRIANGLE;
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pMesh->mPrimitiveTypes &= ~aiPrimitiveType_POLYGON;
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aiFace* out = new aiFace[numOut](), *curOut = out;
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std::vector<aiVector3D> temp_verts3d(max_out+2); /* temporary storage for vertices */
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std::vector<aiVector2D> temp_verts(max_out+2);
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// Apply vertex colors to represent the face winding?
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#ifdef AI_BUILD_TRIANGULATE_COLOR_FACE_WINDING
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if (!pMesh->mColors[0])
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pMesh->mColors[0] = new aiColor4D[pMesh->mNumVertices];
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else
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new(pMesh->mColors[0]) aiColor4D[pMesh->mNumVertices];
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aiColor4D* clr = pMesh->mColors[0];
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#endif
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#ifdef AI_BUILD_TRIANGULATE_DEBUG_POLYS
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FILE* fout = fopen(POLY_OUTPUT_FILE,"a");
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#endif
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const aiVector3D* verts = pMesh->mVertices;
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// use std::unique_ptr to avoid slow std::vector<bool> specialiations
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std::unique_ptr<bool[]> done(new bool[max_out]);
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for( unsigned int a = 0; a < pMesh->mNumFaces; a++) {
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aiFace& face = pMesh->mFaces[a];
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unsigned int* idx = face.mIndices;
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int num = (int)face.mNumIndices, ear = 0, tmp, prev = num-1, next = 0, max = num;
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// Apply vertex colors to represent the face winding?
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#ifdef AI_BUILD_TRIANGULATE_COLOR_FACE_WINDING
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for (unsigned int i = 0; i < face.mNumIndices; ++i) {
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aiColor4D& c = clr[idx[i]];
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c.r = (i+1) / (float)max;
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c.b = 1.f - c.r;
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}
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#endif
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aiFace* const last_face = curOut;
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// if it's a simple point,line or triangle: just copy it
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if( face.mNumIndices <= 3)
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{
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aiFace& nface = *curOut++;
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nface.mNumIndices = face.mNumIndices;
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nface.mIndices = face.mIndices;
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face.mIndices = NULL;
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continue;
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}
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// optimized code for quadrilaterals
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else if ( face.mNumIndices == 4) {
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// quads can have at maximum one concave vertex. Determine
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// this vertex (if it exists) and start tri-fanning from
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// it.
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unsigned int start_vertex = 0;
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for (unsigned int i = 0; i < 4; ++i) {
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const aiVector3D& v0 = verts[face.mIndices[(i+3) % 4]];
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const aiVector3D& v1 = verts[face.mIndices[(i+2) % 4]];
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const aiVector3D& v2 = verts[face.mIndices[(i+1) % 4]];
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const aiVector3D& v = verts[face.mIndices[i]];
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aiVector3D left = (v0-v);
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aiVector3D diag = (v1-v);
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aiVector3D right = (v2-v);
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left.Normalize();
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diag.Normalize();
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right.Normalize();
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const float angle = std::acos(left*diag) + std::acos(right*diag);
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if (angle > AI_MATH_PI_F) {
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// this is the concave point
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start_vertex = i;
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break;
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}
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}
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const unsigned int temp[] = {face.mIndices[0], face.mIndices[1], face.mIndices[2], face.mIndices[3]};
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aiFace& nface = *curOut++;
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nface.mNumIndices = 3;
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nface.mIndices = face.mIndices;
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nface.mIndices[0] = temp[start_vertex];
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nface.mIndices[1] = temp[(start_vertex + 1) % 4];
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nface.mIndices[2] = temp[(start_vertex + 2) % 4];
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aiFace& sface = *curOut++;
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sface.mNumIndices = 3;
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sface.mIndices = new unsigned int[3];
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sface.mIndices[0] = temp[start_vertex];
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sface.mIndices[1] = temp[(start_vertex + 2) % 4];
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sface.mIndices[2] = temp[(start_vertex + 3) % 4];
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// prevent double deletion of the indices field
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face.mIndices = NULL;
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continue;
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}
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else
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{
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// A polygon with more than 3 vertices can be either concave or convex.
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// Usually everything we're getting is convex and we could easily
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// triangulate by tri-fanning. However, LightWave is probably the only
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// modeling suite to make extensive use of highly concave, monster polygons ...
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// so we need to apply the full 'ear cutting' algorithm to get it right.
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// RERQUIREMENT: polygon is expected to be simple and *nearly* planar.
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// We project it onto a plane to get a 2d triangle.
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// Collect all vertices of of the polygon.
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for (tmp = 0; tmp < max; ++tmp) {
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temp_verts3d[tmp] = verts[idx[tmp]];
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}
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// Get newell normal of the polygon. Store it for future use if it's a polygon-only mesh
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aiVector3D n;
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NewellNormal<3,3,3>(n,max,&temp_verts3d.front().x,&temp_verts3d.front().y,&temp_verts3d.front().z);
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if (nor_out) {
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for (tmp = 0; tmp < max; ++tmp)
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nor_out[idx[tmp]] = n;
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}
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// Select largest normal coordinate to ignore for projection
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const float ax = (n.x>0 ? n.x : -n.x);
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const float ay = (n.y>0 ? n.y : -n.y);
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const float az = (n.z>0 ? n.z : -n.z);
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unsigned int ac = 0, bc = 1; /* no z coord. projection to xy */
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float inv = n.z;
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if (ax > ay) {
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if (ax > az) { /* no x coord. projection to yz */
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ac = 1; bc = 2;
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inv = n.x;
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}
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}
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else if (ay > az) { /* no y coord. projection to zy */
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ac = 2; bc = 0;
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inv = n.y;
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}
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// Swap projection axes to take the negated projection vector into account
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if (inv < 0.f) {
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std::swap(ac,bc);
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}
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for (tmp =0; tmp < max; ++tmp) {
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temp_verts[tmp].x = verts[idx[tmp]][ac];
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temp_verts[tmp].y = verts[idx[tmp]][bc];
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done[tmp] = false;
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}
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#ifdef AI_BUILD_TRIANGULATE_DEBUG_POLYS
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// plot the plane onto which we mapped the polygon to a 2D ASCII pic
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aiVector2D bmin,bmax;
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ArrayBounds(&temp_verts[0],max,bmin,bmax);
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char grid[POLY_GRID_Y][POLY_GRID_X+POLY_GRID_XPAD];
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std::fill_n((char*)grid,POLY_GRID_Y*(POLY_GRID_X+POLY_GRID_XPAD),' ');
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for (int i =0; i < max; ++i) {
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const aiVector2D& v = (temp_verts[i] - bmin) / (bmax-bmin);
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const size_t x = static_cast<size_t>(v.x*(POLY_GRID_X-1)), y = static_cast<size_t>(v.y*(POLY_GRID_Y-1));
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char* loc = grid[y]+x;
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if (grid[y][x] != ' ') {
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for(;*loc != ' '; ++loc);
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*loc++ = '_';
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}
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*(loc+::ai_snprintf(loc, POLY_GRID_XPAD,"%i",i)) = ' ';
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}
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for(size_t y = 0; y < POLY_GRID_Y; ++y) {
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grid[y][POLY_GRID_X+POLY_GRID_XPAD-1] = '\0';
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fprintf(fout,"%s\n",grid[y]);
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}
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fprintf(fout,"\ntriangulation sequence: ");
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#endif
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//
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// FIXME: currently this is the slow O(kn) variant with a worst case
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// complexity of O(n^2) (I think). Can be done in O(n).
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while (num > 3) {
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// Find the next ear of the polygon
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int num_found = 0;
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for (ear = next;;prev = ear,ear = next) {
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// break after we looped two times without a positive match
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for (next=ear+1;done[(next>=max?next=0:next)];++next);
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if (next < ear) {
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if (++num_found == 2) {
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break;
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}
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}
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const aiVector2D* pnt1 = &temp_verts[ear],
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*pnt0 = &temp_verts[prev],
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*pnt2 = &temp_verts[next];
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// Must be a convex point. Assuming ccw winding, it must be on the right of the line between p-1 and p+1.
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if (OnLeftSideOfLine2D(*pnt0,*pnt2,*pnt1)) {
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continue;
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}
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// and no other point may be contained in this triangle
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for ( tmp = 0; tmp < max; ++tmp) {
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// We need to compare the actual values because it's possible that multiple indexes in
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// the polygon are referring to the same position. concave_polygon.obj is a sample
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//
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// FIXME: Use 'epsiloned' comparisons instead? Due to numeric inaccuracies in
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// PointInTriangle() I'm guessing that it's actually possible to construct
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// input data that would cause us to end up with no ears. The problem is,
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// which epsilon? If we chose a too large value, we'd get wrong results
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const aiVector2D& vtmp = temp_verts[tmp];
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if ( vtmp != *pnt1 && vtmp != *pnt2 && vtmp != *pnt0 && PointInTriangle2D(*pnt0,*pnt1,*pnt2,vtmp)) {
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break;
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}
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}
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if (tmp != max) {
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continue;
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}
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// this vertex is an ear
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break;
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}
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if (num_found == 2) {
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// Due to the 'two ear theorem', every simple polygon with more than three points must
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// have 2 'ears'. Here's definitely something wrong ... but we don't give up yet.
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//
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// Instead we're continuing with the standard tri-fanning algorithm which we'd
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// use if we had only convex polygons. That's life.
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ASSIMP_LOG_ERROR("Failed to triangulate polygon (no ear found). Probably not a simple polygon?");
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#ifdef AI_BUILD_TRIANGULATE_DEBUG_POLYS
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fprintf(fout,"critical error here, no ear found! ");
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#endif
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num = 0;
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break;
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curOut -= (max-num); /* undo all previous work */
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for (tmp = 0; tmp < max-2; ++tmp) {
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aiFace& nface = *curOut++;
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nface.mNumIndices = 3;
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if (!nface.mIndices)
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nface.mIndices = new unsigned int[3];
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nface.mIndices[0] = 0;
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nface.mIndices[1] = tmp+1;
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nface.mIndices[2] = tmp+2;
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}
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num = 0;
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break;
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}
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aiFace& nface = *curOut++;
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nface.mNumIndices = 3;
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if (!nface.mIndices) {
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nface.mIndices = new unsigned int[3];
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}
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// setup indices for the new triangle ...
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nface.mIndices[0] = prev;
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nface.mIndices[1] = ear;
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nface.mIndices[2] = next;
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// exclude the ear from most further processing
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done[ear] = true;
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--num;
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}
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if (num > 0) {
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// We have three indices forming the last 'ear' remaining. Collect them.
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aiFace& nface = *curOut++;
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nface.mNumIndices = 3;
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if (!nface.mIndices) {
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nface.mIndices = new unsigned int[3];
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}
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for (tmp = 0; done[tmp]; ++tmp);
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nface.mIndices[0] = tmp;
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for (++tmp; done[tmp]; ++tmp);
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nface.mIndices[1] = tmp;
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for (++tmp; done[tmp]; ++tmp);
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nface.mIndices[2] = tmp;
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}
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}
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#ifdef AI_BUILD_TRIANGULATE_DEBUG_POLYS
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for(aiFace* f = last_face; f != curOut; ++f) {
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unsigned int* i = f->mIndices;
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fprintf(fout," (%i %i %i)",i[0],i[1],i[2]);
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}
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fprintf(fout,"\n*********************************************************************\n");
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fflush(fout);
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#endif
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for(aiFace* f = last_face; f != curOut; ) {
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unsigned int* i = f->mIndices;
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// drop dumb 0-area triangles - deactivated for now:
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//FindDegenerates post processing step can do the same thing
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|
//if (std::fabs(GetArea2D(temp_verts[i[0]],temp_verts[i[1]],temp_verts[i[2]])) < 1e-5f) {
|
|
// ASSIMP_LOG_DEBUG("Dropping triangle with area 0");
|
|
// --curOut;
|
|
|
|
// delete[] f->mIndices;
|
|
// f->mIndices = nullptr;
|
|
|
|
// for(aiFace* ff = f; ff != curOut; ++ff) {
|
|
// ff->mNumIndices = (ff+1)->mNumIndices;
|
|
// ff->mIndices = (ff+1)->mIndices;
|
|
// (ff+1)->mIndices = nullptr;
|
|
// }
|
|
// continue;
|
|
//}
|
|
|
|
i[0] = idx[i[0]];
|
|
i[1] = idx[i[1]];
|
|
i[2] = idx[i[2]];
|
|
++f;
|
|
}
|
|
|
|
delete[] face.mIndices;
|
|
face.mIndices = NULL;
|
|
}
|
|
|
|
#ifdef AI_BUILD_TRIANGULATE_DEBUG_POLYS
|
|
fclose(fout);
|
|
#endif
|
|
|
|
// kill the old faces
|
|
delete [] pMesh->mFaces;
|
|
|
|
// ... and store the new ones
|
|
pMesh->mFaces = out;
|
|
pMesh->mNumFaces = (unsigned int)(curOut-out); /* not necessarily equal to numOut */
|
|
return true;
|
|
}
|
|
|
|
#endif // !! ASSIMP_BUILD_NO_TRIANGULATE_PROCESS
|