From ca491836396d955189251af6e1c4ba781dcd9e27 Mon Sep 17 00:00:00 2001 From: Richard Fabian Date: Sun, 14 Jan 2018 14:21:46 +0000 Subject: [PATCH] added ear clipping triangulation --- tiny_obj_loader.h | 167 ++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 162 insertions(+), 5 deletions(-) diff --git a/tiny_obj_loader.h b/tiny_obj_loader.h index 65a9d62..50a45b5 100644 --- a/tiny_obj_loader.h +++ b/tiny_obj_loader.h @@ -971,10 +971,22 @@ static void InitMaterial(material_t *material) { material->unknown_parameter.clear(); } +// code from https://wrf.ecse.rpi.edu//Research/Short_Notes/pnpoly.html +static int pnpoly(int nvert, float *vertx, float *verty, float testx, float testy) +{ + int i, j, c = 0; + for (i = 0, j = nvert-1; i < nvert; j = i++) { + if ( ((verty[i]>testy) != (verty[j]>testy)) && + (testx < (vertx[j]-vertx[i]) * (testy-verty[i]) / (verty[j]-verty[i]) + vertx[i]) ) + c = !c; + } + return c; +} + static bool exportFaceGroupToShape( shape_t *shape, const std::vector > &faceGroup, const std::vector &tags, const int material_id, - const std::string &name, bool triangulate) { + const std::string &name, bool triangulate, const std::vector &v) { if (faceGroup.empty()) { return false; } @@ -990,6 +1002,150 @@ static bool exportFaceGroupToShape( size_t npolys = face.size(); if (triangulate) { +#define ENABLE_EAR_CLIPPING 1 +#if ENABLE_EAR_CLIPPING + // find the two axes to work in + float min_values[3], max_values[3]; + for( size_t k = 0; k < 3; k++ ) { + min_values[k] = (HUGE_VAL); + max_values[k] = -(HUGE_VAL); + } + + for(size_t f = 0; f < npolys; ++f) { + int vi = face[f].v_idx; + for(size_t k = 0; k < 3; k++ ) { + float value = v[size_t(vi)*3+k]; + if( value < min_values[k] ) min_values[k] = value; + if( value > max_values[k] ) max_values[k] = value; + } + } + for(size_t k = 0; k < 3; k++ ) { + max_values[k] -= min_values[k]; + } + size_t axes[2] = { 1, 2 }; + if( max_values[0] > max_values[1] || max_values[0] > max_values[2] ) { + axes[0] = 0; + if( max_values[1] > max_values[2] ) + axes[1] = 1; + } + + real_t area = 0; + for(size_t k = 0; k < npolys; ++k) { + i0 = face[(k+0)%npolys]; + i1 = face[(k+1)%npolys]; + i2 = face[(k+2)%npolys]; + size_t vi0 = size_t(i0.v_idx); + size_t vi1 = size_t(i1.v_idx); + size_t vi2 = size_t(i2.v_idx); + real_t v0x = v[vi0*3+axes[0]]; + real_t v0y = v[vi0*3+axes[1]]; + real_t v1x = v[vi1*3+axes[0]]; + real_t v1y = v[vi1*3+axes[1]]; + real_t v2x = v[vi2*3+axes[0]]; + real_t v2y = v[vi2*3+axes[1]]; + real_t e0x = v1x - v0x; + real_t e0y = v1y - v0y; + real_t e1x = v2x - v1x; + real_t e1y = v2y - v1y; + area += e0x*e1y - e0y*e1x; + } + + int maxRounds = 10; // arbitrary max loop count to protect against unexpected errors + + std::vector remainingFace = face; + size_t guess_vert = 0; + vertex_index ind[3]; + real_t vx[3]; + real_t vy[3]; + while( remainingFace.size() > 3 && maxRounds > 0 ) { + npolys = remainingFace.size(); + if( guess_vert >= npolys ) { + maxRounds -= 1; + guess_vert -= npolys; + } + for( size_t k = 0; k < 3; k++ ) { + ind[k] = remainingFace[(guess_vert+k)%npolys]; + size_t vi = size_t(ind[k].v_idx); + vx[k] = v[vi*3+axes[0]]; + vy[k] = v[vi*3+axes[1]]; + } + real_t e0x = vx[1] - vx[0]; + real_t e0y = vy[1] - vy[0]; + real_t e1x = vx[2] - vx[1]; + real_t e1y = vy[2] - vy[1]; + real_t cross = e0x*e1y - e0y*e1x; + // if an internal angle + if( cross * area < 0.0f ) { guess_vert += 1; continue; } + + // check all other verts in case they are inside this triangle + bool overlap = false; + for( size_t otherVert = 3; otherVert < npolys; ++otherVert ) { + size_t ovi = size_t(remainingFace[(guess_vert+otherVert)%npolys].v_idx); + real_t tx = v[ovi*3+axes[0]]; + real_t ty = v[ovi*3+axes[1]]; + if( pnpoly( 3, vx, vy, tx, ty ) ) { + overlap = true; + break; + } + } + + if( overlap ) { guess_vert += 1; continue; } + + // this triangle is an ear + { + index_t idx0, idx1, idx2; + idx0.vertex_index = ind[0].v_idx; + idx0.normal_index = ind[0].vn_idx; + idx0.texcoord_index = ind[0].vt_idx; + idx1.vertex_index = ind[1].v_idx; + idx1.normal_index = ind[1].vn_idx; + idx1.texcoord_index = ind[1].vt_idx; + idx2.vertex_index = ind[2].v_idx; + idx2.normal_index = ind[2].vn_idx; + idx2.texcoord_index = ind[2].vt_idx; + + shape->mesh.indices.push_back(idx0); + shape->mesh.indices.push_back(idx1); + shape->mesh.indices.push_back(idx2); + + shape->mesh.num_face_vertices.push_back(3); + shape->mesh.material_ids.push_back(material_id); + } + + // remove v1 from the list + size_t removed_vert_index = (guess_vert+1)%npolys; + while( removed_vert_index + 1 < npolys ) { + remainingFace[removed_vert_index] = remainingFace[removed_vert_index+1]; + removed_vert_index += 1; + } + remainingFace.pop_back(); + } + + if( remainingFace.size() == 3 ) { + i0 = remainingFace[0]; + i1 = remainingFace[1]; + i2 = remainingFace[2]; + { + index_t idx0, idx1, idx2; + idx0.vertex_index = i0.v_idx; + idx0.normal_index = i0.vn_idx; + idx0.texcoord_index = i0.vt_idx; + idx1.vertex_index = i1.v_idx; + idx1.normal_index = i1.vn_idx; + idx1.texcoord_index = i1.vt_idx; + idx2.vertex_index = i2.v_idx; + idx2.normal_index = i2.vn_idx; + idx2.texcoord_index = i2.vt_idx; + + shape->mesh.indices.push_back(idx0); + shape->mesh.indices.push_back(idx1); + shape->mesh.indices.push_back(idx2); + + shape->mesh.num_face_vertices.push_back(3); + shape->mesh.material_ids.push_back(material_id); + } + } +#else // Polygon -> triangle fan conversion for (size_t k = 2; k < npolys; k++) { i1 = i2; @@ -1013,6 +1169,7 @@ static bool exportFaceGroupToShape( shape->mesh.num_face_vertices.push_back(3); shape->mesh.material_ids.push_back(material_id); } +#endif } else { for (size_t k = 0; k < npolys; k++) { index_t idx; @@ -1657,7 +1814,7 @@ bool LoadObj(attrib_t *attrib, std::vector *shapes, // this time. // just clear `faceGroup` after `exportFaceGroupToShape()` call. exportFaceGroupToShape(&shape, faceGroup, tags, material, name, - triangulate); + triangulate, v); faceGroup.clear(); material = newMaterialId; } @@ -1712,7 +1869,7 @@ bool LoadObj(attrib_t *attrib, std::vector *shapes, if (token[0] == 'g' && IS_SPACE((token[1]))) { // flush previous face group. bool ret = exportFaceGroupToShape(&shape, faceGroup, tags, material, name, - triangulate); + triangulate, v); (void)ret; // return value not used. if (shape.mesh.indices.size() > 0) { @@ -1749,7 +1906,7 @@ bool LoadObj(attrib_t *attrib, std::vector *shapes, if (token[0] == 'o' && IS_SPACE((token[1]))) { // flush previous face group. bool ret = exportFaceGroupToShape(&shape, faceGroup, tags, material, name, - triangulate); + triangulate, v); if (ret) { shapes->push_back(shape); } @@ -1799,7 +1956,7 @@ bool LoadObj(attrib_t *attrib, std::vector *shapes, } bool ret = exportFaceGroupToShape(&shape, faceGroup, tags, material, name, - triangulate); + triangulate, v); // exportFaceGroupToShape return false when `usemtl` is called in the last // line. // we also add `shape` to `shapes` when `shape.mesh` has already some