LWJGL教程04 - 渲染

渲染管线

在写代码之前，先了解openGL的渲染管线。

顶点数据

顾名思义，三角形各个顶点的数据。

顶点着色器

通过坐标变换，将顶点数据变换到需要的坐标系下。

图元装配

将顶点组装成点，线，面等。

几何着色器

细分着色器

光栅化

将顶点数据转化为像素。

片段着色器

将像素进行最后的着色。

测试与混合

创建着色器

先来创建顶点着色器vertex.vert。

#version 330

layout (location=0) in vec3 position;

void main()
{
    gl_Position = vec4(position, 1.0);
}

再来创建片段着色器fragment.frag。

#version 330

out vec4 fragColor;

void main()
{
    fragColor = vec4(0.0, 0.5, 0.5, 1.0);
}

使用着色器

[imports ...]

public class ShaderProgram {

    private final int programId;

    private int vertexShaderId;

    private int fragmentShaderId;

    public ShaderProgram() throws RuntimeException {
        programId = glCreateProgram();
        if (programId == 0) {
            throw new RuntimeException("Could not create Shader");
        }
    }

    public void createVertexShader(String shaderCode) {
        vertexShaderId = createShader(shaderCode, GL_VERTEX_SHADER);
    }

    public void createFragmentShader(String shaderCode) {
        fragmentShaderId = createShader(shaderCode, GL_FRAGMENT_SHADER);
    }

    protected int createShader(String shaderCode, int shaderType) {
        int shaderId = glCreateShader(shaderType);
        if (shaderId == 0) {
            throw new RuntimeException("Error creating shader. Type: " + shaderType);
        }

        glShaderSource(shaderId, shaderCode);
        glCompileShader(shaderId);

        if (glGetShaderi(shaderId, GL_COMPILE_STATUS) == 0) {
            throw new RuntimeException("Error compiling Shader code: " + glGetShaderInfoLog(shaderId, 1024));
        }

        glAttachShader(programId, shaderId);

        return shaderId;
    }

    public void link() throws RuntimeException {
        glLinkProgram(programId);
        if (glGetProgrami(programId, GL_LINK_STATUS) == 0) {
            throw new RuntimeException("Error linking Shader code: " + glGetProgramInfoLog(programId, 1024));
        }

        if (vertexShaderId != 0) {
            glDetachShader(programId, vertexShaderId);
        }
        if (fragmentShaderId != 0) {
            glDetachShader(programId, fragmentShaderId);
        }

        glValidateProgram(programId);
        if (glGetProgrami(programId, GL_VALIDATE_STATUS) == 0) {
            System.err.println("Warning validating Shader code: " + glGetProgramInfoLog(programId, 1024));
        }

    }

    public void bind() {
        glUseProgram(programId);
    }

    public void unbind() {
        glUseProgram(0);
    }

    public void cleanup() {
        unbind();
        if (programId != 0) {
            glDeleteProgram(programId);
        }
    }
}

还需要一个类来读取文件。

[imports ...]

public class Utils {
    public static String readFile(String filepath) {
        try {
            return Files.readString(Paths.get(filepath));
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
}

在Render中添加ShaderProgram。

[imports ...]

public class Render {
    public static ShaderProgram shaderProgram;

    public static void createRender() {
        [...]
        shaderProgram = new ShaderProgram();
        shaderProgram.createVertexShader(Utils.readFile("src/main/resources/vertex.vert"));
        shaderProgram.createFragmentShader(Utils.readFile("src/main/resources/fragment.frag"));
        shaderProgram.link();
    }

    public static void cleanup() {
        shaderProgram.cleanup();
    }

    [...]
}

现在尝试绘制一点东西。

首先修改ILogic。

public interface ILogic {
    void init();
    void input();
    void render();
    void cleanup();
}

[imports ...]

public class TestLogic implements ILogic {
    float[] vertices;

    @Override
    public void init() {
        vertices = new float[]{
                0.0f,  0.5f, 0.0f,
                -0.5f, -0.5f, 0.0f,
                0.5f, -0.5f, 0.0f
        };

        FloatBuffer verticesBuffer = MemoryUtil.memAllocFloat(vertices.length);
        verticesBuffer.put(vertices).flip();
        vaoId = glGenVertexArrays();
        glBindVertexArray(vaoId);
        vboId = glGenBuffers();
        glBindBuffer(GL_ARRAY_BUFFER, vboId);
        glBufferData(GL_ARRAY_BUFFER, verticesBuffer, GL_STATIC_DRAW);
        glEnableVertexAttribArray(0);
        glVertexAttribPointer(0, 3, GL_FLOAT, false, 0, 0);
        // 解绑VBO
        glBindBuffer(GL_ARRAY_BUFFER, 0);
        // 解绑VAO
        glBindVertexArray(0);
        MemoryUtil.memFree(verticesBuffer);
    }

    int vaoId;
    int vboId;

    @Override
    public void render() {

        Render.shaderProgram.bind();

        // 绑定VAO
        glBindVertexArray(vaoId);

        // 绘制顶点
        glDrawArrays(GL_TRIANGLES, 0, 3);

        // 还原状态
        glBindVertexArray(0);

        Render.shaderProgram.unbind();
    }

    @Override
    public void input() {
        if (Window.isKeyPressed(GLFW.GLFW_KEY_SPACE))
            System.out.println("Space is pressed");
    }

    @Override
    public void cleanup() {

        glDisableVertexAttribArray(0);

        // 删除VBO
        glBindBuffer(GL_ARRAY_BUFFER, 0);
        glDeleteBuffers(vboId);

        // 删除VAO
        glBindVertexArray(0);
        glDeleteVertexArrays(vaoId);
    }
}

还要修改Engine类。

package com.game;

public class Engine {
    [...]

    public void run() {
        [...]
        
        logic.init();
        Render.createRender();
        
        [...]
        while(!Window.windowShouldClose()) {
            [...]

            Render.render();

            logic.render();
            
            [...]
        }
        [...]
    }

    private void cleanup() {
        logic.cleanup();
        Render.cleanup();
        Window.cleanup();
    }
}

测试一下。

经过努力，终于绘制出了第一个三角形。

但是代码写的杂乱无章，还需要修改。

之后将会改进代码。