java - VAO 不使用着色器渲染颜色

Question

我最近开始学习 OpenGL，我一直在尝试编写一个程序，使用带有着色器的 VAO 和 VBO 在屏幕上显示钻石。我的代码主要基于本教程: https://www.opengl.org/wiki/Tutorial2:_VAOs,_VBOs,_Vertex_and_Fragment_Shaders_%28C_/_SDL%29我还使用了教程中的着色器。菱形应该使用顶点数组对象的颜色信息来绘制，但它只是用白色绘制。着色器似乎加载得很好，所以我认为这是我的顶点和缓冲区数组对象的问题。有人可以解释一下为什么我的代码没有按照我的预期工作，或者展示一个如何使用颜色属性数组中的颜色渲染 VAO 的清晰示例。

package windows;

import java.awt.Frame;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.nio.FloatBuffer;
import java.nio.IntBuffer;

import javax.media.opengl.GL2;
import javax.media.opengl.GLAutoDrawable;
import javax.media.opengl.GLCapabilities;
import javax.media.opengl.GLEventListener;
import javax.media.opengl.GLProfile;
import javax.media.opengl.awt.GLCanvas;
import javax.media.opengl.glu.GLU;

import shaders.ShaderControl2;

import com.jogamp.common.nio.Buffers;

public class Test4 implements GLEventListener{

ShaderControl2 sc;
FloatBuffer vertexPos, vertexCol;
IntBuffer vao, vbo; 
GLU glu = new GLU();

public static void main(String[] args){
    GLProfile glp = GLProfile.getDefault();
    GLCapabilities caps = new GLCapabilities(glp);
    GLCanvas canvas = new GLCanvas(caps);

    Test4 t = new Test4();

    canvas.addGLEventListener(t);

    Frame f = new Frame("TEST #4");
    f.setSize(400,400);
    f.add(canvas);
    f.setVisible(true);
    f.addWindowListener(new WindowAdapter(){
        public void windowClosing(WindowEvent e){
            System.exit(0);
        }
    });
}


@Override
public void display(GLAutoDrawable drawable) {
    GL2 gl = drawable.getGL().getGL2();
    gl.glClearColor(0, 0, 0, 1f);
    gl.glClear(GL2.GL_COLOR_BUFFER_BIT);

    sc.useShader(gl);

    gl.glBindVertexArray(vao.get(0));
    gl.glEnableVertexAttribArray(0);
    gl.glEnableVertexAttribArray(1);
    gl.glDrawArrays(GL2.GL_LINE_LOOP, 0 , 4);

    sc.dontUseShader(gl);

}

@Override
public void dispose(GLAutoDrawable drawable) {
    // TODO Auto-generated method stub

}

@Override
public void init(GLAutoDrawable drawable) {
    GL2 gl = drawable.getGL().getGL2();
    System.out.println(gl.glGetString(GL2.GL_VERSION));

    vertexPos = Buffers.newDirectFloatBuffer(8);
    vertexPos.put(new float[]{0f, 1f});
    vertexPos.put(new float[]{1f, 0f});
    vertexPos.put(new float[]{0f, -1f});
    vertexPos.put(new float[]{-1f, 0});
    vertexPos.flip();

    vertexCol = Buffers.newDirectFloatBuffer(12);
    vertexCol.put(new float[]{1f, 0f, 0f});
    vertexCol.put(new float[]{0f, 1f, 0f});
    vertexCol.put(new float[]{0f, 0f, 1f});
    vertexCol.put(new float[]{1f, 1f, 1f});
    vertexCol.flip();

    vao = IntBuffer.allocate(1);
    vbo = IntBuffer.allocate(2);

    gl.glGenVertexArrays(1, vao);
    gl.glGenBuffers(2, vbo);

    int bytesPerFloat = Float.SIZE/Byte.SIZE;

    gl.glBindBuffer(GL2.GL_ARRAY_BUFFER,  vbo.get(0));
    gl.glBufferData(GL2.GL_ARRAY_BUFFER, vertexPos.capacity() * bytesPerFloat, vertexPos, GL2.GL_STATIC_DRAW);

    gl.glBindBuffer(GL2.GL_ARRAY_BUFFER, vbo.get(1));
    gl.glBufferData(GL2.GL_ARRAY_BUFFER, vertexCol.capacity() * bytesPerFloat, vertexCol, GL2.GL_STATIC_DRAW);

    gl.glBindBuffer(GL2.GL_ARRAY_BUFFER, 0);

    gl.glBindVertexArray(vao.get());
    gl.glEnableVertexAttribArray(0);
    gl.glEnableVertexAttribArray(1);

    gl.glBindBuffer(GL2.GL_ARRAY_BUFFER, vbo.get(0));
    gl.glVertexAttribPointer(0, 2, GL2.GL_FLOAT, false, 0, 0);

    gl.glBindBuffer(GL2.GL_ARRAY_BUFFER, vbo.get(1));
    gl.glVertexAttribPointer(1, 3, GL2.GL_FLOAT, false, 0, 0);

    gl.glBindBuffer(GL2.GL_ARRAY_BUFFER, 0);


    sc = new ShaderControl2();
    sc.vSrc = sc.loadShader("v.txt");
    sc.fSrc = sc.loadShader("f.txt");

}

@Override
public void reshape(GLAutoDrawable drawable, int x, int y, int width,
        int height) {

}

}

ShaderControl2代码:

package shaders;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.nio.ByteBuffer;
import java.nio.IntBuffer;

import javax.media.opengl.*;

public class ShaderControl2 {

private int vertexShaderProg, fragmentShaderProg, shaderProg;
public String[] vSrc, fSrc;

public String[] loadShader(String sFile){
    String line = new String();
    StringBuilder fileContent = new StringBuilder();

    try{
        InputStream is = getClass().getResourceAsStream(sFile);
        BufferedReader br = new BufferedReader(new InputStreamReader(is));
        while((line = br.readLine()) != null){
            fileContent.append(line + "\n");
        }
        is.close();
    } catch(Exception e){
        e.printStackTrace();
    }
    System.out.println("Shader file content:\n" + fileContent);
    return new String[]{fileContent.toString()};
}

public void attachShader(GL2 gl){
    IntBuffer isCompiledVS = IntBuffer.allocate(1), isCompiledFS = IntBuffer.allocate(1), isLinked = IntBuffer.allocate(1);
    IntBuffer vLogLength = IntBuffer.allocate(1), fLogLength = IntBuffer.allocate(1), linkLogLength = IntBuffer.allocate(1);
    ByteBuffer vertexInfoLog, fragmentInfoLog, linkInfoLog;
    int size;

    vertexShaderProg = gl.glCreateShader(GL2.GL_VERTEX_SHADER);

    gl.glShaderSource(vertexShaderProg, 1, vSrc, null);
    gl.glCompileShader(vertexShaderProg);

    gl.glGetShaderiv(vertexShaderProg, GL2.GL_COMPILE_STATUS, isCompiledVS);
    if(isCompiledVS.get(0) == 0){
        System.out.println("Failed to compile vertexShaderProg");

        gl.glGetShaderiv(vertexShaderProg, GL2.GL_INFO_LOG_LENGTH, vLogLength); 
        size = vLogLength.get(0);
        vertexInfoLog = ByteBuffer.allocate(size);
        gl.glGetShaderInfoLog(vertexShaderProg, size, vLogLength, vertexInfoLog);

        for(byte b : vertexInfoLog.array()){
            System.err.print((char)b);
        }
    }

    fragmentShaderProg = gl.glCreateShader(GL2.GL_VERTEX_SHADER);

    gl.glShaderSource(fragmentShaderProg, 1, vSrc, null);
    gl.glCompileShader(fragmentShaderProg);

    gl.glGetShaderiv(fragmentShaderProg, GL2.GL_COMPILE_STATUS, isCompiledFS);
    if(isCompiledFS.get(0) == 0){
        System.out.println("Failed to compile fragmentShaderProg");

        gl.glGetShaderiv(fragmentShaderProg, GL2.GL_INFO_LOG_LENGTH, fLogLength);   
        size = fLogLength.get(0);
        fragmentInfoLog = ByteBuffer.allocate(size);
        gl.glGetShaderInfoLog(fragmentShaderProg, size, fLogLength, fragmentInfoLog);

        for(byte b : fragmentInfoLog.array()){
            System.err.print((char)b);
        }

    }

    shaderProg = gl.glCreateProgram();
    gl.glAttachShader(shaderProg, vertexShaderProg);
    gl.glAttachShader(shaderProg, fragmentShaderProg);

    gl.glBindAttribLocation(shaderProg, 0, "in_Position");
    gl.glBindAttribLocation(shaderProg, 1, "in_Color");

    gl.glLinkProgram(shaderProg);

    gl.glGetProgramiv(shaderProg, GL2.GL_LINK_STATUS, isLinked);
    if(isLinked.get(0) == 0){
        System.out.println("Failed to link shaderProg");

        gl.glGetShaderiv(shaderProg, GL2.GL_INFO_LOG_LENGTH, linkLogLength);
        size = linkLogLength.get(0);
        linkInfoLog = ByteBuffer.allocate(size);
        gl.glGetProgramInfoLog(shaderProg, size, linkLogLength, linkInfoLog);

        for(byte b : linkInfoLog.array()){
            System.err.print((char)b);
        }
    }       
}

public int useShader(GL2 gl){
    gl.glUseProgram(shaderProg);
    return shaderProg;
}

public void dontUseShader(GL2 gl){
    gl.glUseProgram(0);
}
}

着色器代码

f.txt:

#version 210
// It was expressed that some drivers required this next line to function properly
precision highp float;

in  vec3 ex_Color;
out vec4 gl_FragColor;

void main(void) {
    // Pass through our original color with full opacity.
    gl_FragColor = vec4(ex_Color,1.0);
}

v.txt:

#version 210
// in_Position was bound to attribute index 0 and in_Color was bound to attribute index 1
in  vec2 in_Position;
in  vec3 in_Color;

// We output the ex_Color variable to the next shader in the chain
out vec3 ex_Color;
void main(void) {
// Since we are using flat lines, our input only had two points: x and y.
// Set the Z coordinate to 0 and W coordinate to 1

gl_Position = vec4(in_Position.x, in_Position.y, 0.0, 1.0);

// GLSL allows shorthand use of vectors too, the following is also valid:
// gl_Position = vec4(in_Position, 0.0, 1.0);
// We're simply passing the color through unmodified

ex_Color = in_Color;
}

Answer 1

您只看到白线的原因是因为根本没有使用着色器程序。

我看不到你在哪里调用附加着色器(你从不调用 sc.attachShader(gl)，我在 init 方法的末尾添加了 sc.attachShader(gl)。

现在会出现很多错误。

在attachshader中，当您创建fragmentShaderProg时，您将其创建为GL_VERTEX_SHADER，它应该是GL_FRAGMENT_SHADER，并且在其下方您将发送顶点着色器的源来代替片段着色器。

GLSL语言的210版本不存在，将其更改为130版本。GLSL版本的问题是它独立于OpenGL版本，https://github.com/mattdesl/lwjgl-basics/wiki/GLSL-Versions

#version 130

现在添加到 init 方法的末尾

sc.attachShader(gl) 

并改变

fragmentShaderProg = gl.glCreateShader(GL2.GL_VERTEX_SHADER);
gl.glShaderSource(fragmentShaderProg, 1, vSrc, null);

对于

fragmentShaderProg = gl.glCreateShader(GL2.GL_FRAGMENT_SHADER);
gl.glShaderSource(fragmentShaderProg, 1, fSrc, null);

现在可以了。