Add basic material exporting :)

core/src/net/sf/openrocket/file/wavefrontobj/export/MtlExpoter.java

@@ -0,0 +1,68 @@
+package net.sf.openrocket.file.wavefrontobj.export;
+
+import net.sf.openrocket.appearance.Appearance;
+import net.sf.openrocket.appearance.defaults.DefaultAppearance;
+import net.sf.openrocket.file.wavefrontobj.DefaultMtl;
+import net.sf.openrocket.file.wavefrontobj.DefaultObj;
+import net.sf.openrocket.rocketcomponent.RocketComponent;
+import net.sf.openrocket.util.Color;
+
+import java.util.List;
+
+/**
+ * Helper class for exporting a rocket component's appearance to an MTL file.
+ *
+ * @author Sibo Van Gool <sibo.vangool@hotmail.com>
+ */
+public class MtlExpoter {
+    private final DefaultObj obj;
+    private final RocketComponent component;
+    private final String materialName;
+    private List<DefaultMtl> materials;
+
+    /**
+     * Export the appearance of a rocket component
+     * <b>NOTE: </b> you still have to call {@link #doExport()} to actually export the appearance.
+     * @param obj The obj file that will use the material
+     * @param component The component to export the appearance of
+     * @param materialName The name of the material to generate
+     * @param materials The list of materials to add the new material(s) to
+     */
+    public MtlExpoter(DefaultObj obj, RocketComponent component, String materialName, List<DefaultMtl> materials) {
+        this.obj = obj;
+        this.component = component;
+        this.materialName = materialName;
+        this.materials = materials;
+    }
+
+    /**
+     * Export the appearance of the component to the MTL file. Also sets the active material group in the OBJ file.
+     */
+    public void doExport() {
+        // Set the active material group
+        obj.setActiveMaterialGroupName(materialName);
+        DefaultMtl material = new DefaultMtl(materialName);
+
+        // Get the component appearance
+        Appearance appearance = component.getAppearance();
+        if (appearance == null) {
+            appearance = DefaultAppearance.getDefaultAppearance(component);
+        }
+
+        // Apply coloring
+        Color color = appearance.getPaint();
+        final float r = color.getRed()/255f;
+        final float g = color.getGreen()/255f;
+        final float b = color.getBlue()/255f;
+        material.setKd(r, g, b);                                // Diffuse color
+        material.setKa(0f, 0f, 0f);                             // No emission
+        material.setKs(1f, 1f, 1f);                             // Use white specular highlights
+        material.setD(color.getAlpha()/255f);                   // Opacity
+        material.setNs((float) appearance.getShine() * 750);    // Shine (max is 1000, but this too strong compared to OpenRocket's max)
+        material.setIllum(2);                                   // Use Phong reflection (specular highlights etc.)
+
+        // TODO: Apply texture
+
+        materials.add(material);
+    }
+}

core/src/net/sf/openrocket/file/wavefrontobj/export/OBJExporterFactory.java

@@ -2,6 +2,8 @@ package net.sf.openrocket.file.wavefrontobj.export;
 
 import de.javagl.obj.ObjWriter;
 import net.sf.openrocket.file.wavefrontobj.CoordTransform;
+import net.sf.openrocket.file.wavefrontobj.DefaultMtl;
+import net.sf.openrocket.file.wavefrontobj.DefaultMtlWriter;
 import net.sf.openrocket.file.wavefrontobj.DefaultObj;
 import net.sf.openrocket.file.wavefrontobj.ObjUtils;
 import net.sf.openrocket.file.wavefrontobj.export.components.BodyTubeExporter;
@@ -94,6 +96,8 @@ public class OBJExporterFactory {
     public void doExport() {
         DefaultObj obj = new DefaultObj();
         Map<String, DefaultObj> objFileMap;
+        Map<DefaultObj, List<DefaultMtl>> materials = new HashMap<>();
+        materials.put(obj, new ArrayList<>());
         boolean exportAsSeparateFiles = this.options.isExportAsSeparateFiles();
 
         if (exportAsSeparateFiles) {
@@ -129,11 +133,13 @@ public class OBJExporterFactory {
             // If separate export, create a new OBJ for each component
             if (exportAsSeparateFiles) {
                 obj = new DefaultObj();
+                materials.put(obj, new ArrayList<>());
             }
 
             // Component exporting
             String groupName = idx + "_" + component.getName();
-            handleComponent(obj, this.configuration, this.options.getTransformer(), component, groupName, this.options.getLOD());
+            handleComponent(obj, this.configuration, this.options.getTransformer(), component, groupName,
+                    materials.get(obj), this.options.getLOD(), options);
 
             // If separate export, add this object to the map of objects to export
             if (exportAsSeparateFiles) {
@@ -169,6 +175,18 @@ public class OBJExporterFactory {
                 ObjUtils.scaleVertices(obj, options.getScaling());
             }
 
+            // Export materials
+            if (options.isExportAppearance()) {
+                String mtlFilePath = FileUtils.removeExtension(filePath) + ".mtl";
+                List<DefaultMtl> mtls = materials.get(obj);
+                try (OutputStream mtlOutputStream = new FileOutputStream(mtlFilePath)) {
+                    DefaultMtlWriter.write(mtls, mtlOutputStream);
+                } catch (IOException e) {
+                    throw new RuntimeException(e);
+                }
+                obj.setMtlFileNames(List.of(mtlFilePath));
+            }
+
             // Write the OBJ file
             writeObj(obj, filePath);
         }
@@ -184,7 +202,8 @@ public class OBJExporterFactory {
 
     @SuppressWarnings("unchecked") // This is safe because of the structure we set up.
     private <T extends RocketComponent> void handleComponent(DefaultObj obj, FlightConfiguration config, CoordTransform transformer,
-                                                             T component, String groupName, ObjUtils.LevelOfDetail LOD) {
+                                                             T component, String groupName, List<DefaultMtl> materials,
+                                                             ObjUtils.LevelOfDetail LOD, OBJExportOptions options) {
         ExporterFactory<T> factory = null;
         Class<?> currentClass = component.getClass();
 
@@ -198,6 +217,12 @@ public class OBJExporterFactory {
             throw new IllegalArgumentException("Unsupported component type: " + component.getClass().getName());
         }
 
+        // Export material
+        if (options.isExportAppearance()) {
+            MtlExpoter mtlExpoter = new MtlExpoter(obj, component, "mat_" + groupName, materials);
+            mtlExpoter.doExport();
+        }
+
         // Export component
         final RocketComponentExporter<T> exporter = factory.create(obj, config, transformer, component, groupName, LOD);
         exporter.addToObj();

core/src/net/sf/openrocket/file/wavefrontobj/export/components/RingComponentExporter.java

@@ -19,6 +19,8 @@ public class RingComponentExporter extends RocketComponentExporter<RingComponent
 
     @Override
     public void addToObj() {
+        obj.setActiveGroupNames(groupName);
+
         final float outerRadius = (float) component.getOuterRadius();
         final float innerRadius = (float) component.getInnerRadius();
         final float length = (float) component.getLength();
@@ -32,7 +34,7 @@ public class RingComponentExporter extends RocketComponentExporter<RingComponent
     private void generateMesh(float outerRadius, float innerRadius, float length, InstanceContext context) {
         // Generate the mesh
         int startIdx = obj.getNumVertices();
-        TubeExporter.addTubeMesh(obj, transformer, groupName, outerRadius, innerRadius, length, LOD);
+        TubeExporter.addTubeMesh(obj, transformer, null, outerRadius, innerRadius, length, LOD);
         int endIdx = Math.max(obj.getNumVertices() - 1, startIdx);    // Clamp in case no vertices were added
 
         // Translate the mesh to the position in the rocket