383 lines
13 KiB
C++
383 lines
13 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) 2006-2009, ASSIMP Development 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 Development 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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* 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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*/
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#include "AssimpPCH.h"
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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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//#define AI_BUILD_TRIANGULATE_COLOR_FACE_WINDING
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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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DefaultLogger::get()->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( TriangulateMesh( pScene->mMeshes[a]))
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bHas = true;
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}
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if (bHas)DefaultLogger::get()->info ("TriangulateProcess finished. All polygons have been triangulated.");
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else DefaultLogger::get()->debug("TriangulateProcess finished. There was nothing to be done.");
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}
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// ------------------------------------------------------------------------------------------------
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// Test whether a point p2 is on the left side of the line formed by p0-p1
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inline bool OnLeftSideOfLine(const aiVector2D& p0, const aiVector2D& p1,const aiVector2D& p2)
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{
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return ( (p1.x - p0.x) * (p2.y - p0.y) - (p2.x - p0.x) * (p1.y - p0.y) ) > 0;
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}
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// ------------------------------------------------------------------------------------------------
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// Test whether a point is inside a given triangle in R2
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inline bool PointInTriangle2D(const aiVector2D& p0, const aiVector2D& p1,const aiVector2D& p2, const aiVector2D& pp)
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{
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// Point in triangle test using baryzentric coordinates
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const aiVector2D v0 = p1 - p0;
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const aiVector2D v1 = p2 - p0;
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const aiVector2D v2 = pp - p0;
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float dot00 = v0 * v0;
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float dot01 = v0 * v1;
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float dot02 = v0 * v2;
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float dot11 = v1 * v1;
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float dot12 = v1 * v2;
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const float invDenom = 1 / (dot00 * dot11 - dot01 * dot01);
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dot11 = (dot11 * dot02 - dot01 * dot12) * invDenom;
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dot00 = (dot00 * dot12 - dot01 * dot02) * invDenom;
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return (dot11 > 0) && (dot00 > 0) && (dot11 + dot00 < 1);
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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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// 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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// Find out how many output faces we'll get
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unsigned int numOut = 0, max_out = 0;
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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 <= 3)
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numOut++;
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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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assert(numOut != pMesh->mNumFaces);
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aiVector3D* nor_out = NULL;
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if (!pMesh->mNormals && pMesh->mPrimitiveTypes == aiPrimitiveType_POLYGON) {
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nor_out = pMesh->mNormals = new aiVector3D[pMesh->mNumVertices];
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}
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aiFace* out = new aiFace[numOut], *curOut = out;
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std::vector<aiVector3D> temp_verts(max_out+2); /* temporary storage for vertices */
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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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// use boost::scoped_array to avoid slow std::vector<bool> specialiations
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boost::scoped_array<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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// if it's a simple primitive, 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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}
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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 trifanning. However, LightWave is probably the only
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// modeller making extensive use of highly concave monster polygons ...
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// so we need to apply the full 'ear cutting' algorithm.
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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 2d data. Working in R3 would
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// also be possible but it's more difficult to implement.
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// Collect all vertices of of the polygon.
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aiVector3D* verts = pMesh->mVertices;
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for (tmp = 0; tmp < max; ++tmp)
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temp_verts[tmp] = verts[idx[tmp]];
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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_verts.front().x,&temp_verts.front().y,&temp_verts.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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//
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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-1?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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const aiVector2D* pnt1 = (const aiVector2D*)&temp_verts[ear],
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*pnt0 = (const aiVector2D*)&temp_verts[prev],
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*pnt2 = (const aiVector2D*)&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 (OnLeftSideOfLine (*pnt0,*pnt2,*pnt1))
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continue;
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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 refering 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 = * ((aiVector2D*) &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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if (tmp != max)
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continue;
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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 someting wrong ... but we don't give up yet.
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//
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// Instead we're continuting with the standard trifanning algorithm which we'd
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// use if we had only convex polygons. That's life.
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DefaultLogger::get()->error("Failed to triangulate polygon (no ear found). Probably not a simple polygon?");
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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] = idx[0];
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nface.mIndices[1] = idx[tmp+1];
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nface.mIndices[2] = idx[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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// setup indices for the new triangle ...
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nface.mIndices[0] = idx[prev];
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nface.mIndices[1] = idx[ear];
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nface.mIndices[2] = idx[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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nface.mIndices = face.mIndices;
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for (tmp = 0; done[tmp]; ++tmp);
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idx[0] = idx[tmp];
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for (++tmp; done[tmp]; ++tmp);
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idx[1] = idx[tmp];
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for (++tmp; done[tmp]; ++tmp);
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idx[2] = idx[tmp];
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}
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}
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face.mIndices = NULL; /* prevent unintended deletion of our awesome results. would be a pity */
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}
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// kill the old faces
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delete [] pMesh->mFaces;
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// ... and store the new ones
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pMesh->mFaces = out;
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pMesh->mNumFaces = (unsigned int)(curOut-out); /* not necessarily equal to numOut */
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return true;
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}
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#endif // !! ASSIMP_BUILD_NO_TRIANGULATE_PROCESS
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