我正在与一些同事（OpenGL 3.3 + GLFW3和ImGui）一起在3D PBR引擎上工作，我们遇到了一个奇怪的错误：应用程序正常进入绘图循环，并且没有任何OpenGL错误（如使用glCheckError()），但屏幕完全空白。奇怪的是，这仅发生在使用Nvidia GeForce GTX 1060作为其图形卡的同事的计算机上（我的两个朋友使用的计算机完全相同）。
经过一些调查，结果发现此错误是由在主循环之前一次调用的函数触发的。长话短说，它使用几个着色器通过帧缓冲区将四边形渲染到纹理绑定。我将问题缩小为glDrawElements调用；在这些计算机上，除了注释掉该行以外，不进行任何其他操作可以固定显示（以显示垃圾显示纹理为代价，而不是绘制调用的预期结果），而其他所有计算机即使未注释该行也可以很好地运行应用程序
罪魁祸首功能如下：
/**
* Returns a texture identifier filled with a precomputed irradiance map calculated
* from a provided, already set up-environment map
*/
GLuint precomputeIrradianceMap(GLuint envMapId)
{
std::cerr << "Precomputing irradiance map ... " << std::endl;
GLuint irradianceVAO, irradianceVBO, irradianceMap,
irradianceVertShader, irradianceFragShader, irradianceProgram, captureFBO,
captureRBO;
GLint aPos_location, env_map;
glGenVertexArrays(1, &irradianceVAO);
glBindVertexArray(irradianceVAO);
glGenBuffers(1, &irradianceVBO);
glBindBuffer(GL_ARRAY_BUFFER, irradianceVBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(quad_vertices), quad_vertices, GL_STATIC_DRAW);
glGenFramebuffers(1, &captureFBO);
glGenRenderbuffers(1, &captureRBO);
glBindFramebuffer(GL_FRAMEBUFFER, captureFBO);
glBindRenderbuffer(GL_RENDERBUFFER, captureRBO);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT24, 320, 320);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, captureRBO);
checkGLerror();
glGenTextures(1, &irradianceMap);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, irradianceMap);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA16F, 320, 320, 0, GL_RGBA, GL_FLOAT, NULL);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glBindTexture(GL_TEXTURE_2D, envMapId);
checkGLerror();
irradianceVertShader = createShaderFromSource(GL_VERTEX_SHADER, "shaders/irradiance_vert.glsl");
irradianceFragShader = createShaderFromSource(GL_FRAGMENT_SHADER, "shaders/irradiance_frag.glsl");
irradianceProgram = glCreateProgram();
glAttachShader(irradianceProgram, irradianceVertShader);
glAttachShader(irradianceProgram, irradianceFragShader);
printShaderLog(irradianceVertShader);
printShaderLog(irradianceFragShader);
glLinkProgram(irradianceProgram);
glUseProgram(irradianceProgram);
checkGLerror();
env_map = glGetUniformLocation(irradianceProgram, "environmentMap");
aPos_location = glGetAttribLocation(irradianceProgram, "aPos");
glEnableVertexAttribArray(aPos_location);
checkGLerror();
glVertexAttribPointer(aPos_location, 3, GL_FLOAT, GL_FALSE, 0, (void *) 0);
glUniform1i(env_map, 0);
checkGLerror();
glViewport(0, 0, 320, 320);
glBindFramebuffer(GL_FRAMEBUFFER, captureFBO);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, irradianceMap, 0);
checkGLerror();
glClearDepth(1.f);
glClearColor(0.f, 0.f, 0.f, 1.f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
checkGLerror();
// This is the culprit
// glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, quad_indices);
glBindFramebuffer(GL_FRAMEBUFFER, 0);
glBindRenderbuffer(GL_RENDERBUFFER, 0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
checkGLerror();
// glDisableVertexAttribArray(aPos_location);
glDeleteShader(irradianceVertShader);
glDeleteShader(irradianceFragShader);
glDeleteProgram(irradianceProgram);
glDeleteFramebuffers(1, &captureFBO);
glDeleteRenderbuffers(1, &captureRBO);
glDeleteBuffers(1, &irradianceVBO);
glDeleteVertexArrays(1, &irradianceVAO);
checkGLerror();
std::cerr << "... done " << std::endl;
return irradianceMap;
}
您可以安全地将checkGLerror()替换为std::cerr << glCheckError() << std::endl。就像我之前说的那样，没有任何OpenGL错误，所有着色器都可以正常编译，而这仅在配备Nvidia GeForce GTX 1060的计算机上无法解决。
其余代码大部分是设置VAO，VBO等，并且渲染循环如下：
while (!glfwWindowShouldClose(window))
{
glfwGetFramebufferSize(window, &display_w, &display_h);
float newRatio = (float)display_w / display_h;
if(ratio != newRatio)
{
ratio = newRatio;
setAspectRatio(p, ratio);
invP = p.inverse();
glViewport(0, 0, display_w, display_h);
}
ImGui_ImplGlfwGL3_NewFrame();
// Rendering + OpenGL rendering
// Draw the skybox, then the model
ImGui::Begin("Physical parameters", NULL, ImGuiWindowFlags_AlwaysAutoResize);
ImGui::SliderFloat("Dielectric specularity", &ds, 0.f, 1.f, "%.3f");
ImGui::SliderFloat("Light intensity", &l0, 0.f, 10.f, "%.2f");
ImGui::Checkbox("Use irradiance map as skybox", &skyOrIrradiance);
ImGui::Checkbox("Debug draw irradiance map", &debugDraw);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, skyOrIrradiance ? irradianceTexture : skybox_texture);
ImGui::End();
Matrix4f v = camera->getMatrix(), invV = v.inverse();
// glClearColor(0.45f, 0.55f, 0.60f, 1.00f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glBindVertexArray(vertex_array_objs[0]);
glUseProgram(skybox_program);
glUniformMatrix4fv(skybox_v_location, 1, GL_FALSE, (const GLfloat *) invV.data());
glUniformMatrix4fv(skybox_p_location, 1, GL_FALSE, (const GLfloat *) invP.data());
glDisable(GL_DEPTH_TEST);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, quad_indices);
glBindVertexArray(vertex_array_objs[1]);
glUseProgram(program);
glUniformMatrix4fv(mv_location, 1, GL_FALSE, (const GLfloat *) v.data());
glUniformMatrix4fv(p_location, 1, GL_FALSE, (const GLfloat *)p.data());
glUniform1f(uDS_location, ds);
glUniform1f(L0_location, l0);
glActiveTexture(GL_TEXTURE0 + model.activeTexturesCount());
glBindTexture(GL_TEXTURE_2D, irradianceTexture);
glUniform1i(irradiance_location, model.activeTexturesCount());
glEnable(GL_DEPTH_TEST);
model.render();
if(debugDraw)
{
displayTexture(irradianceTexture);
displayTexture(skybox_texture, 0.f, -1.f);
}
camera->drawControls();
// Draw basic interface
basicInterface();
ImGui::Render();
ImGui_ImplGlfwGL3_RenderDrawData(ImGui::GetDrawData());
glfwSwapBuffers(window);
glfwPollEvents();
camera->update(window);
}
model.render()如下：
void GltfModel::render() const
{
for(unsigned int i = 0; i < _activeTextures.size(); i++)
{
if(_textureLocations[i] > -1)
{
int j = _activeTextures[i];
glActiveTexture(GL_TEXTURE0 + i);
glBindTexture(GL_TEXTURE_2D, _textureIds[j]);
glUniform1i(_textureLocations[i], i);
}
}
glBindBuffer(GL_ARRAY_BUFFER, _buffers[ARRAY_BUFFER]);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, _buffers[ELEMENT_ARRAY_BUFFER]);
glDrawElements(_drawingMode, _indicesCount, _indicesType, NULL);
}
多谢您的宝贵时间！
EDIT：将glClear(GL_COLOR_BUFFER_BIT)呼叫放在glfwSwapBuffers(window)之前，即使清除颜色已设置为浅蓝色，仍会显示白色屏幕，而罪魁祸首没有注释。注释罪魁祸首行的确显示为浅蓝色屏幕，因此这使我认为这是一个帧缓冲区问题，但我不能确定地说。