1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.geometry.io.euclidean.threed.stl;
18
19 import java.io.Writer;
20 import java.util.List;
21
22 import org.apache.commons.geometry.euclidean.internal.EuclideanUtils;
23 import org.apache.commons.geometry.euclidean.threed.PlaneConvexSubset;
24 import org.apache.commons.geometry.euclidean.threed.Triangle3D;
25 import org.apache.commons.geometry.euclidean.threed.Vector3D;
26 import org.apache.commons.geometry.io.core.utils.AbstractTextFormatWriter;
27 import org.apache.commons.geometry.io.euclidean.threed.FacetDefinition;
28
29 /** Class for writing the text-based (i.e., "ASCII") STL format.
30 * @see <a href="https://en.wikipedia.org/wiki/STL_%28file_format%29#ASCII_STL">ASCII STL</a>
31 */
32 public class TextStlWriter extends AbstractTextFormatWriter {
33
34 /** Space character. */
35 private static final char SPACE = ' ';
36
37 /** Name of the current STL solid. */
38 private String name;
39
40 /** True if an STL solid definition has been written. */
41 private boolean started;
42
43 /** Construct a new instance for writing STL content to the given writer.
44 * @param writer writer to write to
45 */
46 public TextStlWriter(final Writer writer) {
47 super(writer);
48 }
49
50 /** Write the start of an unnamed STL solid definition. This method is equivalent to calling
51 * {@code stlWriter.startSolid(null);}
52 * @throws java.io.UncheckedIOException if an I/O error occurs
53 */
54 public void startSolid() {
55 startSolid(null);
56 }
57
58 /** Write the start of an STL solid definition with the given name.
59 * @param solidName the name of the solid; may be null
60 * @throws IllegalArgumentException if {@code solidName} contains new line characters
61 * @throws IllegalStateException if a solid definition has already been started
62 * @throws java.io.UncheckedIOException if an I/O error occurs
63 */
64 public void startSolid(final String solidName) {
65 if (started) {
66 throw new IllegalStateException("Cannot start solid definition: a solid is already being written");
67 }
68 if (solidName != null && (solidName.indexOf('\r') > -1 || solidName.indexOf('\n') > -1)) {
69 throw new IllegalArgumentException("Solid name cannot contain new line characters");
70 }
71
72 name = solidName;
73 writeBeginOrEndLine(StlConstants.SOLID_START_KEYWORD);
74
75 started = true;
76 }
77
78 /** Write the end of the current STL solid definition. This method is called automatically on
79 * {@link #close()} if needed.
80 * @throws IllegalStateException if no solid definition has been started
81 * @throws java.io.UncheckedIOException if an I/O error occurs
82 */
83 public void endSolid() {
84 if (!started) {
85 throw new IllegalStateException("Cannot end solid definition: no solid has been started");
86 }
87
88 writeBeginOrEndLine(StlConstants.SOLID_END_KEYWORD);
89 name = null;
90 started = false;
91 }
92
93 /** Write the given boundary to the output as triangles.
94 * @param boundary boundary to write
95 * @throws IllegalStateException if no solid has been started yet
96 * @throws java.io.UncheckedIOException if an I/O error occurs
97 * @see PlaneConvexSubset#toTriangles()
98 */
99 public void writeTriangles(final PlaneConvexSubset boundary) {
100 for (final Triangle3D tri : boundary.toTriangles()) {
101 writeTriangles(tri.getVertices(), tri.getPlane().getNormal());
102 }
103 }
104
105 /** Write the given facet definition to the output as triangles.
106 * @param facet facet definition to write
107 * @throws IllegalStateException if no solid has been started yet
108 * @throws java.io.UncheckedIOException if an I/O error occurs
109 * @see #writeTriangle(Vector3D, Vector3D, Vector3D, Vector3D)
110 */
111 public void writeTriangles(final FacetDefinition facet) {
112 writeTriangles(facet.getVertices(), facet.getNormal());
113 }
114
115 /** Write the facet defined by the given vertices and normal to the output as triangles.
116 * If the the given list of vertices contains more than 3 vertices, it is converted to
117 * triangles using a triangle fan. Callers are responsible for ensuring that the given
118 * vertices represent a valid convex polygon.
119 *
120 * <p>If a non-zero normal is given, the vertices are ordered using the right-hand rule,
121 * meaning that they will be in a counter-clockwise orientation when looking down
122 * the normal. If no normal is given, or the given value cannot be normalized, a normal
123 * is computed from the triangle vertices, also using the right-hand rule. If this also
124 * fails (for example, if the triangle vertices do not define a plane), then the
125 * zero vector is used.</p>
126 * @param vertices vertices defining the facet
127 * @param normal facet normal; may be null
128 * @throws IllegalStateException if no solid has been started yet or fewer than 3 vertices
129 * are given
130 * @throws java.io.UncheckedIOException if an I/O error occurs
131 */
132 public void writeTriangles(final List<Vector3D> vertices, final Vector3D normal) {
133 for (final List<Vector3D> triangle : EuclideanUtils.convexPolygonToTriangleFan(vertices, t -> t)) {
134 writeTriangle(
135 triangle.get(0),
136 triangle.get(1),
137 triangle.get(2),
138 normal);
139 }
140 }
141
142 /** Write a triangle to the output.
143 *
144 * <p>If a non-zero normal is given, the vertices are ordered using the right-hand rule,
145 * meaning that they will be in a counter-clockwise orientation when looking down
146 * the normal. If no normal is given, or the given value cannot be normalized, a normal
147 * is computed from the triangle vertices, also using the right-hand rule. If this also
148 * fails (for example, if the triangle vertices do not define a plane), then the
149 * zero vector is used.</p>
150 * @param p1 first point
151 * @param p2 second point
152 * @param p3 third point
153 * @param normal facet normal; may be null
154 * @throws IllegalStateException if no solid has been started yet
155 * @throws java.io.UncheckedIOException if an I/O error occurs
156 */
157 public void writeTriangle(final Vector3D p1, final Vector3D p2, final Vector3D p3, final Vector3D normal) {
158 if (!started) {
159 throw new IllegalStateException("Cannot write triangle: no solid has been started");
160 }
161
162 write(StlConstants.FACET_START_KEYWORD);
163 write(SPACE);
164 writeVector(StlUtils.determineNormal(p1, p2, p3, normal));
165 writeNewLine();
166
167 write(StlConstants.OUTER_KEYWORD);
168 write(SPACE);
169 write(StlConstants.LOOP_START_KEYWORD);
170 writeNewLine();
171
172 writeTriangleVertex(p1);
173
174 if (StlUtils.pointsAreCounterClockwise(p1, p2, p3, normal)) {
175 writeTriangleVertex(p2);
176 writeTriangleVertex(p3);
177 } else {
178 writeTriangleVertex(p3);
179 writeTriangleVertex(p2);
180 }
181
182 write(StlConstants.LOOP_END_KEYWORD);
183 writeNewLine();
184
185 write(StlConstants.FACET_END_KEYWORD);
186 writeNewLine();
187 }
188
189 /** {@inheritDoc} */
190 @Override
191 public void close() {
192 if (started) {
193 endSolid();
194 }
195
196 super.close();
197 }
198
199 /** Write a triangle vertex to the output.
200 * @param vertex triangle vertex
201 * @throws java.io.UncheckedIOException if an I/O error occurs
202 */
203 private void writeTriangleVertex(final Vector3D vertex) {
204 write(StlConstants.VERTEX_KEYWORD);
205 write(SPACE);
206 writeVector(vertex);
207 writeNewLine();
208 }
209
210 /** Write a vector to the output.
211 * @param vec vector to write
212 * @throws java.io.UncheckedIOException if an I/O error occurs
213 */
214 private void writeVector(final Vector3D vec) {
215 write(vec.getX());
216 write(SPACE);
217 write(vec.getY());
218 write(SPACE);
219 write(vec.getZ());
220 }
221
222 /** Write the beginning or ending line of the solid definition.
223 * @param keyword keyword at the start of the line
224 * @throws java.io.UncheckedIOException if an I/O error occurs
225 */
226 private void writeBeginOrEndLine(final String keyword) {
227 write(keyword);
228 write(SPACE);
229
230 if (name != null) {
231 write(name);
232 }
233
234 writeNewLine();
235 }
236 }