Question

我正在尝试使用OpenGL Superbibel（第6版）学习现代OpenGL。由于我的主要编程语言是java，我使用的是jogl。

我遇到问题，显示旋转立方体，只显示12个三角形中的3个。每次列表的前3个（如果我注释掉一些顶点，将使用下一个顶点）。

主要问题：

为什么只显示12个三角形中的3个？

结果是这样的：

顶点着色器：

#version 420 core

layout (location = 1) in vec4 position;

out VS_OUT{
    vec4 color;
} vs_out;

uniform mat4 mv_matrix;
uniform mat4 proj_matrix;

void main(void){
   gl_Position = proj_matrix * mv_matrix * position;
   vs_out.color = position * 2.0 + vec4(0.5, 0.5, 0.5, 0.0);
}

Fragment Shader：

#version 420 core

out vec4 color;
in VS_OUT{
  vec4 color;
} fs_in;

void main(void){
  color = fs_in.color;
}

Java代码：（从init方法中的应用程序类调用启动，在显示方法内部渲染）。

public class Listening9 extends GLApplication {
    private int[] buffer = new int[1];
    float aspect = 0.0f;
    float[] proj_matrix = new float[16];
    int mv_location;
    int proj_location;
    float st = 0.001f;

    public Listening9() {
        super();
    }

    @Override
    protected void render(GL4 gl4, float time) {
        time = st;
        gl4.glViewport(0, 0, GLApplication.windowSize.width, GLApplication.windowSize.height);
        gl4.glClearColor(0.0f, 0.25f, 0.0f, 1.0f);
        gl4.glClearDepthf(1.0f);
        gl4.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT);

        gl4.glUseProgram(program);
        gl4.glUniformMatrix4fv(proj_location, 1, false, proj_matrix, 0);

        float f = (float)time * 0.3f;
        Matrix4 mv_matrix = new Matrix4();
        mv_matrix.translate(0.0f, 0.0f, -20.0f);
        mv_matrix.translate((float)Math.sin(2.1f * f) * 0.5f,
                             (float)Math.cos(1.7f * f) * 0.5f,
                             (float)( Math.sin(1.3f * f) * Math.cos(1.5f * f)) * 2.0f);
        mv_matrix.rotate((float)time * 45.0f, 0.0f, 1.0f, 0.0f);
        mv_matrix.rotate((float)time * 81.0f, 1.0f, 0.0f, 0.0f);
        gl4.glUniformMatrix4fv(mv_location, 1, false, mv_matrix.getMatrix(), 0);
        gl4.glDrawArrays(GL.GL_TRIANGLES, 0, 36);



        checkError(gl4, "display");
    }

    @Override
    protected void startup(GL4 gl4) {
        program = loadProgram(gl4, new String[] { "l9vs", "l9fs" }, new int[] {
                GL4.GL_VERTEX_SHADER, GL4.GL_FRAGMENT_SHADER });


        mv_location = gl4.glGetUniformLocation(program, "mv_matrix");
        proj_location = gl4.glGetUniformLocation(program, "proj_matrix");
        System.out.println("MV: "+mv_location);
        System.out.println("Proj: "+proj_location);

        gl4.glGenVertexArrays(1, objects, Semantic.Object.VAO);
        gl4.glBindVertexArray(objects[Semantic.Object.VAO]);

        float vertex_positions[] = { 
                -0.25f,  0.25f, -0.25f,
                -0.25f, -0.25f, -0.25f,
                 0.25f, -0.25f, -0.25f,

                 0.25f, -0.25f, -0.25f,
                 0.25f,  0.25f, -0.25f,
                -0.25f,  0.25f, -0.25f,

                 0.25f, -0.25f, -0.25f,
                 0.25f, -0.25f,  0.25f,
                 0.25f,  0.25f, -0.25f,

                 0.25f, -0.25f,  0.25f,
                 0.25f,  0.25f,  0.25f,
                 0.25f,  0.25f, -0.25f,

                 0.25f, -0.25f,  0.25f,
                -0.25f, -0.25f,  0.25f,
                 0.25f,  0.25f,  0.25f,

                -0.25f, -0.25f,  0.25f,
                -0.25f,  0.25f,  0.25f,
                 0.25f,  0.25f,  0.25f,

                -0.25f, -0.25f,  0.25f,
                -0.25f, -0.25f, -0.25f,
                -0.25f,  0.25f,  0.25f,

                -0.25f, -0.25f, -0.25f,
                -0.25f,  0.25f, -0.25f,
                -0.25f,  0.25f,  0.25f,

                -0.25f, -0.25f,  0.25f,
                 0.25f, -0.25f,  0.25f,
                 0.25f, -0.25f, -0.25f,

                 0.25f, -0.25f, -0.25f,
                -0.25f, -0.25f, -0.25f,
                -0.25f, -0.25f,  0.25f,

                -0.25f,  0.25f, -0.25f,
                 0.25f,  0.25f, -0.25f,
                 0.25f,  0.25f,  0.25f,

                 0.25f,  0.25f,  0.25f,
                -0.25f,  0.25f,  0.25f,
                -0.25f,  0.25f, -0.25f};


        gl4.glGenBuffers(1, buffer, 0);
        gl4.glBindBuffer(GL.GL_ARRAY_BUFFER, buffer[0]);
        gl4.glBufferData(GL.GL_ARRAY_BUFFER,
                     vertex_positions.length,
                     FloatBuffer.wrap(vertex_positions),
                     GL.GL_STATIC_DRAW);
        gl4.glVertexAttribPointer(1, 3, GL.GL_FLOAT, false, 0, 0);
        gl4.glEnableVertexAttribArray(1);

        //gl4.glEnable(GL.GL_CULL_FACE);
        gl4.glFrontFace(GL.GL_CW);

        gl4.glEnable(GL.GL_DEPTH_TEST);
        gl4.glDepthFunc(GL.GL_LEQUAL);

    }

    @Override
    protected void shutdown(GL4 gl4) {
        gl4.glDeleteProgram(program);
        gl4.glDeleteVertexArrays(1, objects, objects[Semantic.Object.VAO]);
    }

    @Override
    protected void onResize(GL4 gl4, int w, int h) {
        aspect = w / h;
        proj_matrix = FloatUtil.makePerspective(proj_matrix,
                0,
                true,
                50.0f,
                aspect,
                0.1f,
                1000.0f);

    }

    private int loadProgram(GL4 gl, String[] names, int[] types) {
        ShaderProgram shaderProgram = new ShaderProgram();

        for (int i = 0; i < names.length; i++) {
            shaderProgram.add(loadShader(gl, types[i], names[i]));
        }

        shaderProgram.init(gl);

        int id = shaderProgram.program();

        shaderProgram.link(gl, System.out);

        checkError(gl, "initProgram");
        System.out.println("Program loaded! (" + id + ")");
        return id;
    }

    private ShaderCode loadShader(GL4 gl, int type, String name) {
        return ShaderCode.create(gl, type, this.getClass(), SHADERS_ROOT, null,
                name, "sl", null, true);
    }

    public static void main(String[] args) {
        new Listening9();
    }

    @Override
    protected void onUP() {
        st += 0.001f;
    }

}

Answer 1

根据请求：问题似乎是（请参阅问题评论）glBufferData的第二个参数需要缓冲区大小（以字节为单位）。由于缓冲区由浮点元素组成，因此您需要指定vertex_positions.length * 4而不是vertex_positions.length（浮点数的大小为4个字节）。

Answer 2

您对glBufferData的来电缺少数据格式。在C ++中，您应该使用sizeof-operator动态读取大小，如下所示：

    gl4.glBufferData(GL.GL_ARRAY_BUFFER,
                 vertex_positions.length*sizeof(GLfloat),
                 FloatBuffer.wrap(vertex_positions),
                 GL.GL_STATIC_DRAW);

您还应该将vertex_positions的类型从float更改为GLfloat，因为此数据类型在不同的计算机上具有相同的大小（4字节）。 float可能会有所不同。

OpenGL仅显示12个三角形中的3个

2 个答案: