objectloader.java

JAVA游戏编程光盘,内有18个实例,非常详细地阐述了JAVA游戏编程的知识.

package com.brackeen.javagamebook.math3D;

import java.io.*;
import java.util.*;
import com.brackeen.javagamebook.graphics3D.texture.*;

/**
    The ObjectLoader class loads a subset of the
    Alias|Wavefront OBJ file specification.

    Lines that begin with '#' are comments.

    OBJ file keywords:
    <pre>
    mtllib [filename]    - Load materials from an external .mtl
                           file.
    v [x] [y] [z]        - Define a vertex with floating-point
                           coords (x,y,z).
    f [v1] [v2] [v3] ... - Define a new face. a face is a flat,
                           convex polygon with vertices in
                           counter-clockwise order. Positive
                           numbers indicate the index of the
                           vertex that is defined in the file.
                           Negative numbers indicate the vertex
                           defined relative to last vertex read.
                           For example, 1 indicates the first
                           vertex in the file, -1 means the last
                           vertex read, and -2 is the vertex
                           before that.
    g [name]             - Define a new group by name. The faces
                           following are added to this group.
    usemtl [name]        - Use the named material (loaded from a
                           .mtl file) for the faces in this group.
    </pre>

    MTL file keywords:
    <pre>
    newmtl [name]        - Define a new material by name.
    map_Kd [filename]    - Give the material a texture map.
    </pre>
*/
public class ObjectLoader {

    /**
        The Material class wraps a ShadedTexture.
    */
    public static class Material {
        public File sourceFile;
        public ShadedTexture texture;
    }


    /**
        A LineParser is an interface to parse a line in a text
        file. Separate LineParsers and are used for OBJ and MTL
        files.
    */
    protected interface LineParser {
        public void parseLine(String line) throws IOException,
            NumberFormatException, NoSuchElementException;
    }

    protected File path;
    protected List vertices;
    protected Material currentMaterial;
    protected HashMap materials;
    protected List lights;
    protected float ambientLightIntensity;
    protected HashMap parsers;
    private PolygonGroup object;
    private PolygonGroup currentGroup;

    /**
        Creates a new ObjectLoader.
    */
    public ObjectLoader() {
        materials = new HashMap();
        vertices = new ArrayList();
        parsers = new HashMap();
        parsers.put("obj", new ObjLineParser());
        parsers.put("mtl", new MtlLineParser());
        currentMaterial = null;
        setLights(new ArrayList(), 1);
    }

    /**
        Sets the lights used for the polygons in the parsed
        objects. After calling this method calls to loadObject
        use these lights.
    */
    public void setLights(List lights,
        float ambientLightIntensity)
    {
        this.lights = lights;
        this.ambientLightIntensity = ambientLightIntensity;
    }


    /**
        Loads an OBJ file as a PolygonGroup.
    */
    public PolygonGroup loadObject(String filename)
        throws IOException
    {
        File file = new File(filename);
        object = new PolygonGroup();
        object.setFilename(file.getName());
        path = file.getParentFile();

        vertices.clear();
        currentGroup = object;
        parseFile(filename);

        return object;
    }


    /**
        Gets a Vector3D from the list of vectors in the file.
        Negative indeces count from the end of the list, postive
        indeces count from the beginning. 1 is the first index,
        -1 is the last. 0 is invalid and throws an exception.
    */
    protected Vector3D getVector(String indexStr) {
        int index = Integer.parseInt(indexStr);
        if (index < 0) {
            index = vertices.size() + index + 1;
        }
        return (Vector3D)vertices.get(index-1);
    }


    /**
        Parses an OBJ (ends with ".obj") or MTL file (ends with
        ".mtl").
    */
    protected void parseFile(String filename)
        throws IOException
    {
        // get the file relative to the source path
        File file = new File(path, filename);
        BufferedReader reader = new BufferedReader(
            new FileReader(file));

        // get the parser based on the file extention
        LineParser parser = null;
        int extIndex = filename.lastIndexOf('.');
        if (extIndex != -1) {
            String ext = filename.substring(extIndex+1);
            parser = (LineParser)parsers.get(ext.toLowerCase());
        }
        if (parser == null) {
            parser = (LineParser)parsers.get("obj");
        }

        // parse every line in the file
        while (true) {
            String line = reader.readLine();
            // no more lines to read
            if (line == null) {
                reader.close();
                return;
            }

            line = line.trim();

            // ignore blank lines and comments
            if (line.length() > 0 && !line.startsWith("#")) {
                // interpret the line
                try {
                    parser.parseLine(line);
                }
                catch (NumberFormatException ex) {
                    throw new IOException(ex.getMessage());
                }
                catch (NoSuchElementException ex) {
                    throw new IOException(ex.getMessage());
                }
            }

        }
    }


    /**
        Parses a line in an OBJ file.
    */
    protected class ObjLineParser implements LineParser {

        public void parseLine(String line) throws IOException,
            NumberFormatException, NoSuchElementException
        {
            StringTokenizer tokenizer = new StringTokenizer(line);
            String command = tokenizer.nextToken();
            if (command.equals("v")) {
                // create a new vertex
                vertices.add(new Vector3D(
                    Float.parseFloat(tokenizer.nextToken()),
                    Float.parseFloat(tokenizer.nextToken()),
                    Float.parseFloat(tokenizer.nextToken())));
            }
            else if (command.equals("f")) {
                // create a new face (flat, convex polygon)
                List currVertices = new ArrayList();
                while (tokenizer.hasMoreTokens()) {
                    String indexStr = tokenizer.nextToken();

                    // ignore texture and normal coords
                    int endIndex = indexStr.indexOf('/');
                    if (endIndex != -1) {
                        indexStr = indexStr.substring(0, endIndex);
                    }

                    currVertices.add(getVector(indexStr));
                }

                // create textured polygon
                Vector3D[] array =
                    new Vector3D[currVertices.size()];
                currVertices.toArray(array);
                TexturedPolygon3D poly =
                    new TexturedPolygon3D(array);

                // set the texture
                ShadedSurface.createShadedSurface(
                    poly, currentMaterial.texture,
                    lights, ambientLightIntensity);

                // add the polygon to the current group
                currentGroup.addPolygon(poly);
            }
            else if (command.equals("g")) {
                // define the current group
                if (tokenizer.hasMoreTokens()) {
                    String name = tokenizer.nextToken();
                    currentGroup = new PolygonGroup(name);
                }
                else {
                    currentGroup = new PolygonGroup();
                }
                object.addPolygonGroup(currentGroup);
            }
            else if (command.equals("mtllib")) {
                // load materials from file
                String name = tokenizer.nextToken();
                parseFile(name);
            }
            else if (command.equals("usemtl")) {
                // define the current material
                String name = tokenizer.nextToken();
                currentMaterial = (Material)materials.get(name);
                if (currentMaterial == null) {
                    System.out.println("no material: " + name);
                }
            }
            else {
                // unknown command - ignore it
            }

        }
    }


    /**
        Parses a line in a material MTL file.
    */
    protected class MtlLineParser implements LineParser {

        public void parseLine(String line)
            throws NoSuchElementException
        {
            StringTokenizer tokenizer = new StringTokenizer(line);
            String command = tokenizer.nextToken();

            if (command.equals("newmtl")) {
                // create a new material if needed
                String name = tokenizer.nextToken();
                currentMaterial = (Material)materials.get(name);
                if (currentMaterial == null) {
                    currentMaterial = new Material();
                    materials.put(name, currentMaterial);
                }
            }
            else if (command.equals("map_Kd")) {
                // give the current material a texture
                String name = tokenizer.nextToken();
                File file = new File(path, name);
                if (!file.equals(currentMaterial.sourceFile)) {
                    currentMaterial.sourceFile = file;
                    currentMaterial.texture = (ShadedTexture)
                        Texture.createTexture(file.getPath(),true);
                }
            }
            else {
                // unknown command - ignore it
            }
        }
    }
}