如何在OpenGL中设置特定比例？

vsmadaxz  于 2024-01-07  发布在  其他
关注(0)|答案(1)|浏览(269)

我使用C++和OpenGL。但我需要对象缩放到一定的比例。对于一个游戏引擎。我的目标只是为了比例设置而不是改变。

  1. #define GLFW_INCLUDE_NONE
  2. #include <glm/glm.hpp>
  3. #include <glm/gtc/type_ptr.hpp>
  4. #include <GLFW/glfw3.h>
  5. #include <Glad/glad.h>
  6. #include "vendor/ImGui/imgui.h"
  7. #include "vendor/ImGui/backends/imgui_impl_glfw.h"
  8. #include "vendor/ImGui/backends/imgui_impl_opengl3.h"
  9. #include <stdio.h>
  10. #define WINDOW_WIDTH 640
  11. #define WINDOW_HEIGHT 480
  13. void error_callback(int error, const char* description)
  14. {
  15.     fprintf(stderr, "Error: %s\n", description);
  16. }
  18. const char* vertexShaderSource = "#version 330 core\n"
  19. "layout(location = 0) in vec3 aPos;\n"
  20. "uniform mat4 projection;\n"
  21. "void main()\n"
  22. "{\n"
  23. "  gl_Position = projection * vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
  24. "}\0";
  26. const char* fragmentShaderSource =
  27. "#version 330 core\n"
  28. "out vec4 FragColor;\n"
  29. "uniform vec2 wsize;\n"
  30. "void main()\n"
  31. "{\n"
  32. " vec2 position = gl_FragCoord.xy;\n"
  33. " FragColor = vec4(position.x/wsize.x, position.x/position.y/wsize.x,position.y/wsize.y, 1.0f);\n"
  34. "}\n\0";
  36. float aspectRatio;
  37. glm::mat4 projection;
  39. void framebuffer_size_callback(GLFWwindow* window, int width, int height)
  40. {
  41.     glViewport(0, 0, width, height);
  42.     aspectRatio = (float)width / (float)height;
  43.     projection = glm::ortho(-aspectRatio, aspectRatio, -1.0f, 1.0f, -1.0f, 1.0f);
  44. }
  46. int main()
  47. {
  48.     if (!glfwInit())
  49.     {
  50.         // Initialization failed
  51.     }
  52.     glfwSetErrorCallback(error_callback);
  54.     glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
  55.     glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
  56.     glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
  57.     GLFWwindow* window = glfwCreateWindow(640, 480, "GL YA!", NULL, NULL);
  58.     if (!window)
  59.     {
  60.         // Window or context creation failed
  61.     }
  63.     glfwMakeContextCurrent(window);
  64.     gladLoadGL();
  66.     glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
  68.     float vertices[9 * 2] = {
  69.         -0.5f, -0.5f, 0.0f,
  70.         0.5f, -0.5f, 0.0f,
  71.         0.5f, 0.5f, 0.0f,
  73.         0.5f, 0.5f, 0.0f,
  74.         -0.5f, 0.5f, 0.0f,
  75.         -0.5f, -0.5f, 0.0f,
  76.     };
  78.     glfwSwapInterval(1);
  80.     GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
  81.     glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
  82.     glCompileShader(vertexShader);
  84.     GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
  85.     glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
  86.     glCompileShader(fragmentShader);
  88.     GLuint shaderProgram = glCreateProgram();
  89.     glAttachShader(shaderProgram, vertexShader);
  90.     glAttachShader(shaderProgram, fragmentShader);
  91.     glLinkProgram(shaderProgram);
  93.     glDeleteShader(vertexShader);
  94.     glDeleteShader(fragmentShader);
  96.     GLuint VBO;
  97.     glGenBuffers(1, &VBO);
  98.     glBindBuffer(GL_ARRAY_BUFFER, VBO);
  99.     glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
  101.     GLuint VAO;
  102.     glGenVertexArrays(1, &VAO);
  103.     glBindVertexArray(VAO);
  105.     glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
  106.     glEnableVertexAttribArray(0);
  107.     IMGUI_CHECKVERSION();
  108.     ImGui::CreateContext();
  109.     ImGuiIO& io = ImGui::GetIO(); (void)io;
  110.     io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;    // Enable Keyboard Controls
  111.     io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;     // Enable Gamepad Controls
  112.     io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;
  113.     io.ConfigDockingWithShift = false;
  114.     ImGui::StyleColorsDark();
  115.     const char* glsl_version = "#version 100";
  116.     ImGui_ImplGlfw_InitForOpenGL(window, true);
  117.     ImGui_ImplOpenGL3_Init(glsl_version);
  118.     float x = 0;
  119.     float y = 0;
  120.     float z = 0;
  122.     while (!glfwWindowShouldClose(window))
  123.     {
  124.         int width, height;
  125.         glfwGetFramebufferSize(window, &width, &height);
  127.         framebuffer_size_callback(window, width, height);
  129.         ImGui_ImplOpenGL3_NewFrame();
  130.         ImGui_ImplGlfw_NewFrame();
  131.         ImGui::NewFrame();
  133.         ImGui::DockSpaceOverViewport(ImGui::GetMainViewport(), ImGuiDockNodeFlags_PassthruCentralNode);
  135.         ImGui::Begin("Hello OpenGL!");
  136.         ImGui::InputFloat("X", &x);
  137.         ImGui::InputFloat("Y", &y);
  138.         ImGui::InputFloat("Z", &z);
  139.         ImGui::End();
  140.         ImGui::Render();
  142.         glViewport(0, 0, width, height);
  144.         glClear(GL_COLOR_BUFFER_BIT);
  146.         //Square
  148.         glUseProgram(shaderProgram);
  149.         GLint wsize = glGetUniformLocation(shaderProgram, "wsize");
  150.         glUniform2f(wsize, width, height);
  151.         /*
  152.         glm::mat4 transform = glm::mat4(1.0f); // Start with an identity matrix
  153.         transform = glm::translate(transform, glm::vec3(x, y, z)); // Move the triangle along the x and y axes
  155.         for (int i = 0; i < 9 * 2; i += 3) {
  156.             glm::vec4 vertex = transform * glm::vec4(vertices[i], vertices[i + 1], vertices[i + 2], 1.0f);
  157.             vertices[i] = vertex.x;
  158.             vertices[i + 1] = vertex.y;
  159.             vertices[i + 2] = vertex.z;
  160.         }
  161.         */
  162.         float currentX = 0.0f;
  163.         float currentY = 0.0f;
  164.         float currentZ = 0.0f;
  166.         for (int i = 0; i < 9 * 2; i += 3) {
  167.             currentX += vertices[i];
  168.             currentY += vertices[i + 1];
  169.             currentZ += vertices[i + 2];
  170.         }
  172.         currentX /= 9;
  173.         currentY /= 9;
  174.         currentZ /= 9;
  176.         float tx = x - currentX;
  177.         float ty = y - currentY;
  178.         float tz = z - currentZ;
  180.         for (int i = 0; i < 9 * 2; i += 3) {
  181.             vertices[i] += tx;
  182.             vertices[i + 1] += ty;
  183.             vertices[i + 2] += tz;
  184.         }
  186.         for (int i = 0; i < 9 * 2; i += 3) {
  187.             vertices[i] += x;
  188.             vertices[i + 1] += y;
  189.             vertices[i + 2] += z;
  190.         }
  192.         glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
  194.         glUniformMatrix4fv(glGetUniformLocation(shaderProgram, "projection"), 1, GL_FALSE, glm::value_ptr(projection));
  195.         glBindVertexArray(VAO);
  196.         glDrawArrays(GL_TRIANGLES, 0, 6);
  198.         //ImGui
  199.         ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
  201.         glfwSwapBuffers(window);
  202.         glfwPollEvents();
  203.     }
  205.     glfwDestroyWindow(window);
  206.     glfwTerminate();
  207. }

字符串
我不知道该怎么做。我想有一个确切的变量设置，而不是改变大小。我正在寻找一个解决方案，使用glm，我会把一切都在以后的类。

opengl

1条答案

按热度按时间
kmpatx3s

kmpatx3s1#

如果你有一个网格的顶点数据，并且想缩放对象而不迭代网格数据，那么一个解决方案就是让着色器为你做。
为此，我们只需要在顶点着色器中引入一个统一变量。
在应用变换之前，我们首先必须缩放顶点位置，例如。

  1. //vertex shader
  3. in vec3 aPos;             //position coords
  4. uniform vec3 uScale;      //scale factor
  5. uniform mat4 uProjection; //projection matrix
  7. int main()
  8. {
  9.     gl_Position = uProjection * vec4(aPos * uScale, 1.0);
  10. }

字符串
通常，这是通过一个变换矩阵来完成的，该矩阵是投影、视图和模型矩阵（因此是mvp矩阵）的结果。

***投影：**透视、正交或截头体
*视图：：例如lookAt，基于摄像机的位置、目标和向上矢量
模型：对象位置、 比例 * 和/或旋转

然后在顶点着色器中，有一个称为uMVP的统一体或两个统一体，一个用于投影和视图（修改频率较低，至少不是针对每个对象），一个模型矩阵对于每个对象可能不同（不同的位置，缩放和/或旋转）。
例如

  1. //vertex shader
  3. in vec3 aPos;
  4. uniform mat4 uProjection;
  5. uniform mat4 uView;
  6. uniform mat4 uModel;
  8. void main()
  9. {
  10.     gl_Position = uProjection * uView * uModel * vec4(aPos, 1.0);
  11. }

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