为什么我在 OpenGL (3) 中的三角形不使用 lwjgl 渲染？

Question

So i started to learn lwjgl recently, and quickly realized that I need to improve in OpenGL to continue. I followed tutorial here and tried to implement same code using java and lwjgl (code in tutorial is in C++). I successfully managed to replicate OpenGL calls from tutorial using lwjgl api, but when I start my program i see only black screen and nothing else =( No triangle, nothing. No errors in console ether.

My Window.java class where i perform OpenGL rendering (Never mind Spring annotations, i'm just using IoC container to manage objects, method run() is called after Spring context creation):

import com.gitlab.cvazer.dnd.map.desktop.ashlesy.Orchestrator;
import com.gitlab.cvazer.dnd.map.desktop.render.Camera;
import com.gitlab.cvazer.dnd.map.desktop.util.Shaders;
import lombok.Getter;
import lombok.extern.slf4j.Slf4j;
import org.lwjgl.Version;
import org.lwjgl.glfw.GLFWErrorCallback;
import org.lwjgl.opengl.GL;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import java.io.IOException;
import java.util.Objects;

import static org.lwjgl.glfw.Callbacks.glfwFreeCallbacks;
import static org.lwjgl.glfw.GLFW.*;
import static org.lwjgl.opengl.GL30.*;
import static org.lwjgl.system.MemoryUtil.NULL;

@Slf4j
@Component
public class Window {
    private @Autowired Shaders shaders;
    private @Getter long window;

    //START HERE!
    public void run() {
        new Thread(() -> {
            log.info("Hello LWJGL " + Version.getVersion() + "!");
            init();
            try {
                loop();
            } catch (IOException e) {
                e.printStackTrace();
            }
            glfwFreeCallbacks(window);
            glfwDestroyWindow(window);
            glfwTerminate();
            Objects.requireNonNull(glfwSetErrorCallback(null)).free();
        }).start();
    }

    private void init() {
        GLFWErrorCallback.createPrint(System.err).set();
        if ( !glfwInit() ) throw new IllegalStateException("Unable to initialize GLFW");
        glfwDefaultWindowHints();
        glfwWindowHint(GLFW_VISIBLE, GLFW_FALSE);
        glfwWindowHint(GLFW_RESIZABLE, GLFW_TRUE);
        glfwWindowHint(GLFW_SAMPLES, 8);
        glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
        glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
        glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
        window = glfwCreateWindow(800, 600, "Hello World!", NULL, NULL);
        if ( window == NULL ) throw new RuntimeException("Failed to create the GLFW window");
        callbacks();
        glfwMakeContextCurrent(window);
        glfwSwapInterval(1);
        glfwShowWindow(window);
    }

    private void loop() throws IOException {
        GL.createCapabilities();

        int vertexArray = glGenVertexArrays();
        glBindVertexArray(vertexArray);

        int vertexBuffer = glGenBuffers();
        glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);

        float[] data = {-1.0f, -1.0f, 0.0f,
                1.0f, -1.0f, 0.0f,
                0.0f,  1.0f, 0.0f};

        glBufferData(GL_ARRAY_BUFFER, data, GL_STATIC_DRAW);

        int program = shaders.loadShaders("vertex.glsl", "fragment.glsl");

        glClearColor(0.0f, 0.0f, 0.0f, 0.0f);

        long lastTime = System.currentTimeMillis();
        while ( !glfwWindowShouldClose(window) ) {
            long delta = System.currentTimeMillis() - lastTime;
            lastTime = System.currentTimeMillis();

            glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
            glUseProgram(program);

            glEnableVertexAttribArray(0);
            glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
            glVertexAttribPointer(0,3,GL_FLOAT, false, 0, vertexBuffer);
            glDrawArrays(GL_TRIANGLES, 0, 3);
            glDisableVertexAttribArray(0);

            glfwSwapBuffers(window); // swap the color buffers
            glfwPollEvents();
        }
    }
}

Shaders.java class:

import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Service;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;

import static org.lwjgl.opengl.GL30.*;

@Slf4j
@Service
public class Shaders {
    public int loadShaders(String vertexFilePath, String fragmentFilePath) throws IOException {
        int vertexShader = glCreateShader(GL_VERTEX_SHADER);
        int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);

        String vertexCode = Files.lines(Paths.get(vertexFilePath))
                .collect(Collectors.joining("\n"));

        String fragmentCode = Files.lines(Paths.get(fragmentFilePath))
                .collect(Collectors.joining("\n"));

        compileShader(vertexShader, vertexCode);
        compileShader(fragmentShader, fragmentCode);

        int program = glCreateProgram();
        glAttachShader(program, vertexShader);
        glAttachShader(program, fragmentShader);
        glLinkProgram(program);

        glDetachShader(program, vertexShader);
        glDetachShader(program, fragmentShader);

        glDeleteShader(vertexShader);
        glDeleteShader(fragmentShader);

        return program;
    }

    private void compileShader(int shader, String code){
        glShaderSource(shader, code);
        glCompileShader(shader);
        String slog = glGetShaderInfoLog(shader);
        if (slog.contentEquals("")) return;
        log.info(slog);
    }
}

vertex.glsl file:

#version 330 core
layout(location = 0) in vec3 vertexPosition_modelspace;
void main(){
  gl_Position.xyz = vertexPosition_modelspace;
  gl_Position.w = 1.0;
}

fragment.glsl file:

#version 330 core
out vec3 color;
void main(){
  color = vec3(1,0,0);
}

I followed part 1 (coding OpenGL calls) and 2 (coding GLSL shaders, loading them) of this tutorial, but adding shaders didn't fixed my problem

I don't think that googling further can give me answers since almost all tutorials online on topic of lwjgl use OpenGL 1 for rendering.

How can i make this work?

Answer 1

The issue is the line

glVertexAttribPointer(0,3,GL_FLOAT, false, 0, vertexBuffer);

If a named buffer object is bound then the last parameter of glVertexAttribPointer is treated as a byte offset into the buffer object's data store.

When you use glVertexAttribPointer then you don't have to specify the vertex buffer by a parameter. The function associates the vertex attribute to the buffer object, which is currently bound to the target GL_ARRAY_BUFFER .

It has to be:

glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
glVertexAttribPointer(0, 3, GL_FLOAT, false, 0, 0);

See also Java Code Examples for org.lwjgl.opengl.GL20.glVertexAttribPointer()