尝试 glUseProgram 时出现 Opengl 错误 1281

Question

关于如何进一步调试此 opengl 错误的任何想法？ 1281

我正在从文件加载源代码、编译、链接，然后在 glUseProgram 之后尝试检查错误

在我对象的绘制方法中..

log.info(gl2.glIsProgram(shaderProgram)); // true
gl2.glUseProgram(shaderProgram);

int error;
while ((error = gl2.glGetError()) != GL2.GL_NO_ERROR) {
    throw new RuntimeException("glUseProgram" + ": glError " + error);
}

输出..

[13:38:08] INFO (IARectangle.java:99) - true
java.lang.RuntimeException: glUseProgram: glError 1281

这就是我从 .glsl 文件加载我的着色器源代码的方式..

Vector<Integer> shaders = new Vector<Integer>();

try {

    shaders.add(compileSource(
        loadSource("shaders/vertexShader.glsl"),
        loadSource("shaders/fragmentShader.glsl")));

    return shaders;

} catch (Exception e) {
    e.printStackTrace();
    return shaders;
}

public String[] loadSource(String filename){

    StringBuilder sb = new StringBuilder();
    try {

        InputStream is = getClass().getClassLoader().getResourceAsStream(filename);
        BufferedReader br = new BufferedReader(new InputStreamReader(is, "UTF-8"));
        String line;
        while ((line = br.readLine()) != null) {

            sb.append(line);
            sb.append('\n');
        }
        is.close();

    } catch (Exception e) {
        e.printStackTrace();
    }

    return new String[] { sb.toString() };
}

public final int compileSource(final String[] vertexSource, final String[] fragmentSource) throws Exception {

     vertexShaderProgram;
    int fragmentShaderProgram;
    int shaderProgram;

    // load vertexShader source, compile and verify
    vertexShaderProgram = gl2.glCreateShader(GL2.GL_VERTEX_SHADER);
    gl2.glShaderSource(vertexShaderProgram, 1, vertexSource, null, 0);
    gl2.glCompileShader(vertexShaderProgram);
    verifyCompile(gl2, vertexShaderProgram);

    // load fragmentShader source, compile and verify
    fragmentShaderProgram = gl2.glCreateShader(GL2.GL_FRAGMENT_SHADER);
    gl2.glShaderSource(fragmentShaderProgram, 1, fragmentSource, null, 0);
    gl2.glCompileShader(fragmentShaderProgram);
    verifyCompile(gl2, fragmentShaderProgram);

    shaderProgram = gl2.glCreateProgram();

    gl2.glAttachShader(shaderProgram, vertexShaderProgram);
    gl2.glAttachShader(shaderProgram, fragmentShaderProgram);
    gl2.glLinkProgram(shaderProgram);
    IntBuffer intBuffer = IntBuffer.allocate(1);
    gl2.glGetProgramiv(shaderProgram, GL2.GL_LINK_STATUS, intBuffer);

    if (intBuffer.get(0) != 1){

        String infoLog = null;
        gl2.glGetProgramiv(shaderProgram, GL2.GL_INFO_LOG_LENGTH, intBuffer);
        int size = intBuffer.get(0);
        log.error("Program link error: ");
        if (size > 0) {

            ByteBuffer byteBuffer = ByteBuffer.allocate(size);
            gl2.getGL2().glGetProgramInfoLog(shaderProgram, size, intBuffer, byteBuffer);
            byte[] sizeBytes = new byte[size];
            byteBuffer.get(sizeBytes, 0, size);
            infoLog = new String(sizeBytes);

            log.error("info: " + infoLog);

        } else {
            log.error("Unknown");
        }
        System.exit(1);
        return shaderProgram;

    } else {

        return shaderProgram;
    }
}

顶点着色器源..

#version 120

uniform mat4 uMVPMatrix;
attribute vec4 vPosition;

void main() {
    gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
    //gl_Position = uMVPMatrix * vPosition;
}

片段着色器源..

#version 120

uniform vec4 vColor;

void main() {
    gl_FragColor = vColor;
}

Answer 1

乍一看，我不确定为什么 glGetError 会返回错误代码。但是为了回答您的具体问题“我怎样才能进一步调试此错误？”，我确实有一个建议。

将您的绘制代码更改为:

// Logging errors before the call to glUseProgram
int error;
while ((error = gl2.glGetError()) != GL2.GL_NO_ERROR) {
    log.info(error);
}

log.info(gl2.glIsProgram(shaderProgram)); // true
gl2.glUseProgram(shaderProgram);

int error;
while ((error = gl2.glGetError()) != GL2.GL_NO_ERROR) {
    throw new RuntimeException("glUseProgram" + ": glError " + error);
}

请注意，此处的不同之处在于我们添加了一段代码来记录 glGetError 在调用 glUseProgram 之前返回的错误。原因是因为错误不一定源自您对 glUseProgram 的调用。如果您看到使用上述代码记录的 1281 错误，则可以确定该错误实际上源自 glUseProgram 调用之前进行的 OpenGL 调用。

看看 documentation对于 glGetError:

glGetError returns the value of the error flag. Each detectable error is assigned a numeric code and symbolic name. When an error occurs, the error flag is set to the appropriate error code value. No other errors are recorded until glGetError is called, the error code is returned, and the flag is reset to GL_NO_ERROR.

因此，如果您之前的 OpenGL 调用之一(例如，可能是您的 compileSource 函数中的某些内容)记录了 1281 错误，而您没有调用 glGetError 在该点和您对 glUseProgram 的调用之间的任何位置，您不能合理地假设该错误实际上源自 glUseProgram 调用。

总之，glGetError 不会返回 OpenGL 调用记录的最新错误。您需要更精细地调用 glGetError，以便查明错误的来源。这将使您能够解决遇到的问题并准确确定记录错误的 OpenGL 调用。