OpenGL Triange 演示显示空白窗口

OpenGL Triange demo shows blank window

提问人：part1kl 提问时间：3/19/2023 最后编辑：Rabbid76part1kl 更新时间：3/19/2023 访问量：72

问：

我通过三角形演示开始学习 LWJGL3 和 OpenGL 3.2+。该程序似乎运行良好，我没有收到任何 OpenGL 错误，但三角形没有显示在屏幕上。

我在这里查看了一些类似的问题，其中许多问题的确定问题是缺少 VAO 或三角形坐标或着色器错误，但我已经在我的代码中检查了这些问题。创建 VAO，分配绑定和顶点属性。三角形坐标实际上应该构成一个三角形，我的着色器说它们已经正确编译和链接。我对我在这里错过的东西感到茫然。

这是我的代码。所有内容都在这个文件中（三角形顶点数据、OpenGL 对象 ID 和底部的着色器源代码），除了 LWJGL 本身和我用于矩阵的 com.hackoeur.jglm 库：

package net.part1kl;

import com.hackoeur.jglm.Mat4;
import com.hackoeur.jglm.Matrices;
import org.lwjgl.Version;
import org.lwjgl.glfw.*;
import static org.lwjgl.glfw.GLFW.*;
import org.lwjgl.opengl.GL;
import java.nio.FloatBuffer;
import java.nio.IntBuffer;
import static org.lwjgl.opengl.GL30C.*;
import static org.lwjgl.system.MemoryUtil.*;


public class Demo {

    public static void main(String[] args) {
        init();
        loop();
        dispose();
    }

    private static long window;

    private static void init(){
        /* Initialize GLFW */
        System.out.println(Version.getVersion());
        glfwSetErrorCallback(GLFWErrorCallback.createPrint(System.err));
        if (!glfwInit()) throw new IllegalStateException("GLFW Init Failed");

        /* Set window hints and create window */
        glfwDefaultWindowHints();
        glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
        glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2);
        glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
        glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GLFW_TRUE);
        glfwWindowHint(GLFW_RESIZABLE, GLFW_FALSE);
        glfwWindowHint(GLFW_VISIBLE, GLFW_FALSE);
        window = glfwCreateWindow(600, 600, "Demo", NULL, NULL);
        if ( window == NULL) { glfwTerminate(); throw new RuntimeException("Window Creation Failed"); }

        /* Other window setup */
        glfwSetWindowPos(window, 200, 200);
        glfwMakeContextCurrent(window);
        GL.createCapabilities();
        glfwSwapInterval(1);
        glfwSetKeyCallback(window, (window, key, scancode, action, mods) -> {
            if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS) glfwSetWindowShouldClose(window, true);
        });
        glfwShowWindow(window);

        /* Create and bind VAO */
        vao = glGenVertexArrays();
        glBindVertexArray(vao);

        /* Create, bind, and populate VBO */
        vbo = glGenBuffers();
        glBindBuffer(GL_ARRAY_BUFFER, vbo);
        FloatBuffer verts = memAllocFloat(vertices.length);
        for (float val : vertices) verts.put(val);
        verts.flip();
        glBufferData(GL_ARRAY_BUFFER, verts, GL_STATIC_DRAW);
        memFree(verts);

        /* Create Vertex Shader */
        vShader = glCreateShader(GL_VERTEX_SHADER);
        glShaderSource(vShader, vertexSource);
        glCompileShader(vShader);
        if (glGetShaderi(vShader, GL_COMPILE_STATUS) != GL_TRUE) throw new RuntimeException(glGetShaderInfoLog(vShader));

        /* Create Fragment Shader */
        fShader = glCreateShader(GL_FRAGMENT_SHADER);
        glShaderSource(fShader, fragmentSource);
        glCompileShader(fShader);
        if (glGetShaderi(fShader, GL_COMPILE_STATUS) != GL_TRUE) throw new RuntimeException(glGetShaderInfoLog(fShader));

        /* Create Shader Program */
        program = glCreateProgram();
        glAttachShader(program, vShader);
        glAttachShader(program, fShader);
        glBindFragDataLocation(program, 0, "fragColor");
        glLinkProgram(program);
        if (glGetProgrami(program, GL_LINK_STATUS) != GL_TRUE) throw new RuntimeException(glGetProgramInfoLog(program));
        glUseProgram(program);

        /* Set pointer for vertex position information */
        int pAttr = glGetAttribLocation(program, "position");
        glEnableVertexAttribArray(pAttr);
        glVertexAttribPointer(pAttr, 3, GL_FLOAT, false, 6 * Float.BYTES, 0);

        /* Set pointer for vertex color information */
        int cAttr = glGetAttribLocation(program, "color");
        glEnableVertexAttribArray(cAttr);
        glVertexAttribPointer(cAttr, 3, GL_FLOAT, false, 6 * Float.BYTES, 3 * Float.BYTES);

        /* Create and set model uniform. Using com.hackoeur.jglm v1.0.0 for matrices. */
        Mat4 model = new Mat4();
        int uModel = glGetUniformLocation(program, "model");
        glUniformMatrix4fv(uModel, false, (FloatBuffer)model.getBuffer().flip());

        /* Create and set view uniform */
        Mat4 view = new Mat4();
        int uView = glGetUniformLocation(program, "view");
        glUniformMatrix4fv(uView, false, (FloatBuffer)view.getBuffer().flip());

        /* Get window size ratio for projection */
        IntBuffer width = memAllocInt(1);
        IntBuffer height = memAllocInt(1);
        GLFW.glfwGetFramebufferSize(window, width, height);
        float ratio = width.get() / (float) height.get();
        memFree(width); memFree(height);

        /* Create and set projection uniform */
        Mat4 projection = Matrices.ortho(-ratio, ratio, -1f, 1f, -1f, 1f);
        int uProjection = glGetUniformLocation(program, "projection");
        glUniformMatrix4fv(uProjection, false, (FloatBuffer)projection.getBuffer().flip());
    }

    private static void loop(){
        double lastTime = glfwGetTime();
        double time = lastTime;
        while(!glfwWindowShouldClose(window)){
            double delta = (float) (time - lastTime);

            glClear(GL_COLOR_BUFFER_BIT);

            glBindVertexArray(vao);
            glBindBuffer(GL_ARRAY_BUFFER, vbo);
            glUseProgram(program);


            glDrawArrays(GL_TRIANGLES, 0, 3);

            glfwSwapBuffers(window);
            glfwPollEvents();

            glCheck();

            lastTime = time;
            time = glfwGetTime();
        }
    }

    private static void dispose(){
        glDeleteVertexArrays(vao);
        glDeleteBuffers(vbo);
        glDeleteShader(vShader);
        glDeleteShader(fShader);
        glDeleteProgram(program);

        glfwDestroyWindow(window);
    }

    private static void print(String message) { System.out.println(message); }

    private static void err(String message) { System.err.println(message); }

    private static int glCheckCounter = 0;

    private static void glCheck() {
        int val = glGetError();
        if (val==0) print("GL Error Check "+glCheckCounter+" no error.");
        else err("GL Error Check "+glCheckCounter+" returned error "+val);
        glCheckCounter++;
    }


    private static int vao, vbo, vShader, fShader, program;
    private static final float[] vertices = {
            -0.6f,   -0.4f,   0f,   1f,   0f,   0f,
             0.6f,   -0.4f,   0f,   0f,   1f,   0f,
               0f,    0.6f,   0f,   0f,   0f,   1f
    };
    private static final CharSequence vertexSource
            = "#version 150 core\n"
            + "\n"
            + "in vec3 position;\n"
            + "in vec3 color;\n"
            + "\n"
            + "out vec3 vertexColor;\n"
            + "\n"
            + "uniform mat4 model;\n"
            + "uniform mat4 view;\n"
            + "uniform mat4 projection;\n"
            + "\n"
            + "void main() {\n"
            + "    vertexColor = color;\n"
            + "    mat4 mvp = projection * view * model;\n"
            + "    gl_Position = mvp * vec4(position, 1.0);\n"
            + "}";
    private static final CharSequence fragmentSource
            = "#version 150 core\n"
            + "\n"
            + "in vec3 vertexColor;\n"
            + "\n"
            + "out vec4 fragColor;\n"
            + "\n"
            + "void main() {\n"
            + "    fragColor = vec4(vertexColor, 1.0);\n"
            + "}";
}

这是我从运行这个程序中得到的输出：

3.3.1 build 7
GL Error Check 0 no error.
GL Error Check 1 no error.
GL Error Check 2 no error.
GL Error Check 3 no error.
GL Error Check 4 no error.
GL Error Check 5 no error.
GL Error Check 6 no error.
GL Error Check 7 no error.

只要程序运行，“GL Error Check # no error.” 就会一直运行，我已经在 8 个循环中切断了它。它从未出现过 OpenGL 错误。

java lwjgl opengl-3

评论

1赞 Erdal Küçük 3/19/2023
是否返回单位矩阵？new Mat4()

答：

3赞 Rabbid76 3/19/2023 #1

new Mat4()不构造单位矩阵。可以使用单个参数 1.0f 构造单位矩阵：

Mat4 model = new Mat4();

Mat4 model = new Mat4(1.0f);

Mat4 view = new Mat4();

Mat4 view = new Mat4(1.0f);

评论

0赞 part1kl 3/19/2023
谢谢，我为每个调用添加了 1.0f。不幸的是，在进行此更改后，三角形仍然没有显示。
1赞 part1kl 3/19/2023 #2

问题似乎出在 Mat4 对象创建缓冲区的方式上。这是我的IDE为com.hackoeur.jglm.Mat4.getBuffer（）反编译的源代码：

    public FloatBuffer getBuffer() {
        FloatBuffer buffer = this.allocateFloatBuffer();
        int startPos = buffer.position();
        buffer.put(this.m00).put(this.m01).put(this.m02).put(this.m03);
        buffer.put(this.m10).put(this.m11).put(this.m12).put(this.m13);
        buffer.put(this.m20).put(this.m21).put(this.m22).put(this.m23);
        buffer.put(this.m30).put(this.m31).put(this.m32).put(this.m33);
        buffer.position(startPos);
        return buffer;
    }

我不是 100% 确定它的问题是什么，或者我是否只是用错了，但是当我回到我最初由 SilverTiger 遵循的教程的源代码并在那里使用 Matrix4f 对象时，三角形出现了。silvertiger.tutorial.lwjgl.math.Matrix4f.toBuffer（） 的源代码：

    public void toBuffer(FloatBuffer buffer) {
        buffer.put(m00).put(m10).put(m20).put(m30);
        buffer.put(m01).put(m11).put(m21).put(m31);
        buffer.put(m02).put(m12).put(m22).put(m32);
        buffer.put(m03).put(m13).put(m23).put(m33);
        buffer.flip();
    }

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