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我有一小段代码根据传递给它的模型创建一个 ModelInstance 等（请原谅所有未使用的变量，例如 w、h、d，它们来自以前的测试）

package com.mygdx.game;

import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.assets.loaders.ModelLoader;
import com.badlogic.gdx.graphics.Color;
import com.badlogic.gdx.graphics.g3d.Model;
import com.badlogic.gdx.graphics.g3d.ModelInstance;
import com.badlogic.gdx.graphics.g3d.attributes.ColorAttribute;
import com.badlogic.gdx.graphics.g3d.loader.ObjLoader;
import com.badlogic.gdx.math.Vector3;
import com.badlogic.gdx.math.collision.BoundingBox;

public class Shape {
    float w,h,d;
    Color clr;
    Vector3 pos;
    Model shape;
    ModelInstance shapeInst;
    BoundingBox bounds;
    boolean empty;
    public Shape(float width, float height, float depth, Color color, Vector3 position, String model){
        empty = false;
        @SuppressWarnings("rawtypes")
        ModelLoader loader = new ObjLoader();
        shape = loader.loadModel(Gdx.files.internal(model));
        w = width;
        h = height;
        d = depth;
        clr = color;
        pos = position;
        shapeInst = new ModelInstance(shape);
        shapeInst.materials.get(0).set(ColorAttribute.createDiffuse(clr));
        shapeInst.transform.setToTranslation(pos);
        shapeInst.calculateBoundingBox(bounds);
    }
    public Shape(){
        empty = true;
    }
}

但是，每当它运行时，我都会收到此错误：

Exception in thread "LWJGL Application" java.lang.NullPointerException
    at com.badlogic.gdx.graphics.g3d.ModelInstance.calculateBoundingBox(ModelInstance.java:383)
    at com.mygdx.game.Shape.<init>(Shape.java:37)
    at com.mygdx.game.worldRenderer.<init>(worldRenderer.java:62)
    at com.mygdx.game.GDXGame.create(GDXGame.java:92)
    at com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop(LwjglApplication.java:136)
    at com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:114)

它似乎无法计算我指定的 ModelInstance 的边界框。Mabye我只是做错了，任何关于如何使用该calculateBoundingBox()方法的建议都将不胜感激

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1 回答 1

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查看方法calculateBoundingBox的源代码（libgdx 是开源的，您可以查看所有代码；-）：

/** Calculate the bounding box of this model instance. This is a potential slow operation, it is advised to cache the result.
 * @param out the {@link BoundingBox} that will be set with the bounds.
 * @return the out parameter for chaining */
public BoundingBox calculateBoundingBox (final BoundingBox out) {
    out.inf(); // here is line 383 !
    return extendBoundingBox(out);
}

堆栈跟踪在第 383 行抱怨 NullPointerException：out.inf();此时我们知道out必须指向 null。

现在让我们看看为什么会这样：检查shapeInst.calculateBoundingBox(bounds);参数 bounds 为 null 行，因为你忘了初始化它。（您刚刚声明了边界，但从未为其赋值）。

于 2014-08-09T06:49:06.447 回答