java - 在 OpenGL 中绘制多个对象

Question

我开始学习 OpenGL。我可以加载 .obj 模型并使用 elementBuffer 绘制它。但我一直坚持一次尝试两种不同的模型。我要绘制的模型在 Entity 类中。 我能找到的大多数教程都只展示了如何加载和绘制单一模型。没有人解释(至少在某种程度上我可以找到/理解)如何处理多个模型。

这是我所有的代码:

public static void main(String[] args) throws LWJGLException, IOException
{
    PixelFormat pixelFormat = new PixelFormat();
    ContextAttribs contextAtrributes = new ContextAttribs(3, 2);
    contextAtrributes.withForwardCompatible(true);
    contextAtrributes.withProfileCore(true);

    Display.setDisplayMode(new DisplayMode(WIDTH, HEIGHT));
    Display.setTitle("Textured quad!");
    Display.create(pixelFormat, contextAtrributes);

    Mouse.create();
    Mouse.setGrabbed(true);
    Keyboard.create();

    glEnable(GL_DEPTH_TEST);
    glEnable(GL_CULL_FACE);

    entity = new Entity("planeTex.obj");
    entity2 = new Entity("modelTex2.obj");

    Shaders.load();
    Textures.load();
    Camera.create(new Vector3f(0, 1, -0.75f), new Vector3f(-50, 0, 20), HEIGHT, WIDTH);

    while (!Display.isCloseRequested())
    {

        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

        entity.draw();
        entity2.draw();

        Display.update();
        Display.sync(60);
    }

}

public class Entity
{
    private int vao, vbo, ebo;
    private int elementSize;

    public Entity(String name)
    {
        vao = glGenVertexArrays();
        glBindVertexArray(vao);
        vbo = glGenBuffers();
        *Load vertex data into buffer*
        glBindBuffer(GL_ARRAY_BUFFER, vbo);
        glBufferData(GL_ARRAY_BUFFER, buffer, GL_STATIC_DRAW);
        ebo = glGenBuffers();
        *load data into elementBuffer*
        *Set elementSize to the element count*
        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
        glBufferData(GL_ELEMENT_ARRAY_BUFFER, elementBuffer, GL_STATIC_DRAW);
    }

    public void draw()
    {
        glBindVertexArray(vao);
        glBindBuffer(GL_ARRAY_BUFFER, vbo);
        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);

        glDrawElements(GL_TRIANGLES, elementSize, GL_UNSIGNED_INT, 0);
    }
}

public class Shaders
{

public static int vertexShader, fragmentShader;
public static int shaderProgram;
public static int uniTrans;

    public static void load()
    {
        vertexShader = glCreateShader(GL_VERTEX_SHADER);
        glShaderSource(vertexShader, loadFile("vertex.shader"));
        glCompileShader(vertexShader);

        fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
        glShaderSource(fragmentShader, loadFile("fragment.shader"));
        glCompileShader(fragmentShader);


        shaderProgram = glCreateProgram();
        glAttachShader(shaderProgram, vertexShader);
        glAttachShader(shaderProgram, fragmentShader);
        glBindFragDataLocation(shaderProgram, 0, "outColor");
        glLinkProgram(shaderProgram);
        glUseProgram(shaderProgram);


        // Specify the layout of the vertex data
        int posAttrib = glGetAttribLocation(shaderProgram, "position");
        glEnableVertexAttribArray(posAttrib);
        glVertexAttribPointer(posAttrib, 3, GL_FLOAT, false, (Float.SIZE / 8) * 8, 0);

        int colAttrib = glGetAttribLocation(shaderProgram, "color");
        glEnableVertexAttribArray(colAttrib);
        glVertexAttribPointer(colAttrib, 3, GL_FLOAT, false, (Float.SIZE / 8) * 8, (Float.SIZE / 8) * 3);

        int texAttrib = glGetAttribLocation(shaderProgram, "texcoord");
        glEnableVertexAttribArray(texAttrib);
        glVertexAttribPointer(texAttrib, 2, GL_FLOAT, false, (Float.SIZE / 8) * 8, (Float.SIZE / 8) * 6);

        uniTrans = glGetUniformLocation(Shaders.shaderProgram, "model");
    }
}

结果是只会绘制最后创建的Entity对象。无论抽签顺序如何。

Answer 1

好吧，我通过放置这个 block 来修复它 //指定顶点数据的布局 int posAttrib = glGetAttribLocation(Shaders.shaderProgram, "position"); glEnableVertexAttribArray(posAttrib); glVertexAttribPointer(posAttrib, 3, GL_FLOAT, false, (Float.SIZE/8) * 8, 0);

    int colAttrib = glGetAttribLocation(Shaders.shaderProgram, "color");
    glEnableVertexAttribArray(colAttrib);
    glVertexAttribPointer(colAttrib, 3, GL_FLOAT, false, (Float.SIZE / 8) * 8, (Float.SIZE / 8) * 3);

    int texAttrib = glGetAttribLocation(Shaders.shaderProgram, "texcoord");
    glEnableVertexAttribArray(texAttrib);
    glVertexAttribPointer(texAttrib, 2, GL_FLOAT, false, (Float.SIZE / 8) * 8, (Float.SIZE / 8) * 6);

在 glDrawElements 方法之前的实体类绘制循环中。将 block 放在其他任何地方都会导致程序崩溃:

"Cannot use offsets when Array Buffer Object is disabled"

否则它什么也不会画。我从 NicolBolas 那里得到了我应该把它放在实体构造函数中的感觉，但正如我所说，它在任何地方都不起作用。