opengl 相关问题

我试图通过 glReadPixels() 获取在 OpenGL 中单击的颜色： #包括 #包括 #包括 #包括我正在尝试通过 glReadPixels() 获取在 OpenGL 中单击的颜色： #include <iostream> #include <glad/glad.h> #include <GLFW/glfw3.h> #include <glm/gtc/matrix_transform.hpp> #include <glm/gtc/type_ptr.hpp> const char *vertexShaderSource = "#version 330 core\n" "layout (location = 0) in vec4 aPos;\n" "uniform mat4 projection;\n" "uniform mat4 model;\n" "void main()\n" "{\n" " gl_Position = projection * model * vec4(aPos.xy, 0.0, 1.0);\n" "}\0"; const char *fragmentShaderSource = "#version 330 core\n" "out vec4 FragColor;\n" "void main()\n" "{\n" " FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n" "}\n\0"; int main() { if (glfwInit()) { glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4); glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0); glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE); } else { std::cout << "glfw failed to initialise" << std::endl; } GLFWwindow *window = glfwCreateWindow(500, 500, "Opengl Selection", NULL, NULL); glfwMakeContextCurrent(window); if (!gladLoadGLLoader((GLADloadproc) glfwGetProcAddress)) { std::cout << "Failed to initialise glad" << std::endl; } glClearColor(0.3f, 0.2f, 0.1f, 1.0f); glViewport(0, 0, 500, 500); unsigned int vertexShader = glCreateShader(GL_VERTEX_SHADER); glShaderSource(vertexShader, 1, &vertexShaderSource, NULL); glCompileShader(vertexShader); int success; char infoLog[512]; glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success); if (!success) { glGetShaderInfoLog(vertexShader, 512, NULL, infoLog); std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl; } unsigned int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER); glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL); glCompileShader(fragmentShader); glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success); if (!success) { glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog); std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl; } unsigned int shaderProgram = glCreateProgram(); glAttachShader(shaderProgram, vertexShader); glAttachShader(shaderProgram, fragmentShader); glLinkProgram(shaderProgram); glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success); if (!success) { glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog); std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl; } glDeleteShader(vertexShader); glDeleteShader(fragmentShader); float vertices[] = { // pos // tex 0.0f, 1.0f, 0.0f, 1.0f, 1.0f, 0.0f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 0.0f, 1.0f, 0.0f }; unsigned int VBO, VAO; glGenVertexArrays(1, &VAO); glGenBuffers(1, &VBO); glBindBuffer(GL_ARRAY_BUFFER, VBO); glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW); glBindVertexArray(VAO); glEnableVertexAttribArray(0); glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 4 * sizeof(float), (void *) 0); glBindBuffer(GL_ARRAY_BUFFER, 0); glBindVertexArray(0); glUseProgram(shaderProgram); glm::mat4 projection = glm::ortho(0.0f, 1000.0f, 1000.0f, 0.0f, -1.0f, 1.0f); glUniformMatrix4fv(glGetUniformLocation(shaderProgram, "projection"), 1, GL_FALSE, glm::value_ptr(projection)); while (!glfwWindowShouldClose(window)) { glfwPollEvents(); glClear(GL_COLOR_BUFFER_BIT); glUseProgram(shaderProgram); // glm::mat4 projection = glm::ortho(0.0f, 500.0f, 500.0f, 0.0f, -1.0f, 1.0f); glm::mat4 model = glm::mat4(1.0f); model = glm::translate(model, glm::vec3(0.0f, 0.0f, 0.0f)); model = glm::scale(model, glm::vec3(100.0f, 100.0f, 0.0f)); glUniformMatrix4fv(glGetUniformLocation(shaderProgram, "model"), 1, GL_FALSE, glm::value_ptr(model)); glBindVertexArray(VAO); glDrawArrays(GL_TRIANGLES, 0, 6); glBindVertexArray(0); glfwSetMouseButtonCallback(window, [](GLFWwindow *window, int button, int action, int mods) { if (action == GLFW_PRESS) { double xPos, yPos; glfwGetCursorPos(window, &xPos, &yPos); glPixelStorei(GL_UNPACK_ALIGNMENT, 1); unsigned char data[4]; glReadPixels(xPos, yPos, 1, 1, GL_RGBA, GL_UNSIGNED_BYTE, data); std::cout << (float) data[0] << " " << (float) data[1] << " " << (float) data[2] << " " << (float) data[ 3] << std::endl; } }); glfwSwapBuffers(window); glfwPollEvents(); } return 0; } 但是，无论我点击哪里，OpenGl 都会返回背景颜色。我相信我在如何在屏幕上渲染正方形方面做错了。问题*是传递给 glfwGetCursorPos 的位置是相对于窗口的 upper-左上角，而传递给 glReadPixels 的位置是相对于窗口的 lower-左角窗户。解决方案是将调用的 y 位置反转为 glReadPixels。 500x500 窗口中位置的值范围为 0 到 499，因此必须从 499 中减去 yPos： glReadPixels(xPos, 499 - yPos, 1, 1, GL_RGBA, GL_UNSIGNED_BYTE, data); 现在，当 xPos 和 yPos < 50. 都返回正方形的颜色 *正如Rabbid76在评论中首先指出的那样。

c++ opengl glfw glm-math glad

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OpenGL - 纹理未正确渲染

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c++ opengl

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