为啥精灵不在 OpenGL 中渲染？

Posted 2023-02-22

【中文标题】为啥精灵不在 OpenGL 中渲染？

【英文标题】：Why is the sprite not rendering in OpenGL?为什么精灵不在 OpenGL 中渲染？

【发布时间】：2018-04-04 12:45:18

【问题描述】：

我正在尝试在 OpenGL 中渲染 2D（屏幕协调）精灵。然而，当我编译它时，它并没有出现。我看到代码很好（甚至没有任何着色器编译错误或任何其他错误）。我还设置了矩阵（我怀疑是导致问题的原因，这就是混乱的开始！！）

顺便说一下，这里是源代码（没有调试，简而言之）：-

main.cpp

// Including all required headers here...

#include <iostream>

#define GLEW_STATIC
#include <GL/glew.h>

#include <GLFW/glfw3.h>

#include "SOIL2/SOIL2.h"

#include <glm/glm.hpp>
#include <glm/gtc/type_ptr.hpp>
#include <glm/gtc/matrix_transform.hpp>

const GLchar * vertexShaderSource =
    "#version 330 core\n"
    "layout(location = 0) in vec4 vertex;\n"
    "out vec2 TexCoords;\n"
    "uniform mat4 model;\n"
    "uniform mat4 projection;\n"
    "void main()\n"
    "\n"
    "TexCoords = vertex.zw;\n"
    "gl_Position = projection * model * vec4(vertex.xy, 0.0, 1.0);\n"
    "\0";

const GLchar * fragmentShaderSource =
    "#version 330 core\n"
    "in vec2 TexCoords;\n"
    "out vec4 color;\n"
    "uniform sampler2D image;\n"
    "uniform vec3 spriteColor;\n"
    "void main()\n"
    "\n"
    "color = vec4(spriteColor, 1.0) * texture(image, TexCoords);\n"
    "\0";

const GLint WIDTH = 800, HEIGHT = 600;

int main()

    glfwInit();

    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GLFW_FALSE);

    glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);

    GLFWwindow *window = glfwCreateWindow(WIDTH, HEIGHT, "Rendering Sprites", nullptr, nullptr);

    int screenWidth, screenHeight;
    glfwGetFramebufferSize(window, &screenWidth, &screenHeight);

    glfwMakeContextCurrent(window);

    glewExperimental = GL_TRUE;
    glewInit();

    glViewport(0, 0, screenWidth, screenHeight);

    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

    GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
    glCompileShader(vertexShader);

    GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
    glCompileShader(fragmentShader);

    GLuint shaderProgram = glCreateProgram();
    glAttachShader(shaderProgram, vertexShader);
    glAttachShader(shaderProgram, fragmentShader);
    glLinkProgram(shaderProgram);

    glDeleteShader(vertexShader);
    glDeleteShader(fragmentShader);

    GLuint quadVAO;
    GLuint VBO;
    GLfloat vertices[] =
    
        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
    ;

    glGenVertexArrays(1, &quadVAO);
    glGenBuffers(1, &VBO);

    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

    glBindVertexArray(quadVAO);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 4 * sizeof(GLfloat), (GLvoid*)0);
    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glBindVertexArray(0);

    GLuint texture;

    int width, height;

    glGenTextures(1, &texture);
    glBindTexture(GL_TEXTURE_2D, texture);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

    unsigned char *image = SOIL_load_image("img.png", &width, &height, 0, SOIL_LOAD_RGBA);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, image);
    SOIL_free_image_data(image);
    glBindTexture(GL_TEXTURE_2D, 0);

    while (!glfwWindowShouldClose(window))
    
        glfwPollEvents();

        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);

        glUseProgram(shaderProgram);
        glm::mat4 model;
        glm::mat4 projection = glm::ortho(0.0f, static_cast<GLfloat>(WIDTH), static_cast<GLfloat>(HEIGHT), 0.0f, -1.0f, 1.0f);

        glm::vec2 size = glm::vec2(10.0f, 10.0f);
        glm::vec2 position = glm::vec2(-10.0f, 10.0f);
        glm::vec3 color = glm::vec3(1.0f, 0.0f, 0.0f);
        GLfloat rotation = 0.0f;

        model = glm::translate(model, glm::vec3(position, 0.0f));

        model = glm::translate(model, glm::vec3(0.5f * size.x, 0.5f * size.y, 0.0f));
        model = glm::rotate(model, rotation, glm::vec3(0.0f, 0.0f, 1.0f));
        model = glm::translate(model, glm::vec3(-0.5f * size.x, -0.5f * size.y, 0.0f));

        model = glm::scale(model, glm::vec3(size, 1.0f));

        glUniformMatrix4fv(glGetUniformLocation(shaderProgram, "projection"), 1, GL_FALSE, glm::value_ptr(projection));
        glUniformMatrix4fv(glGetUniformLocation(shaderProgram, "model"), 1, GL_FALSE, glm::value_ptr(model));
        glUniform3f(glGetUniformLocation(shaderProgram, "spriteColor"), color.x, color.y, color.z);

        glActiveTexture(GL_TEXTURE0);
        glBindTexture(GL_TEXTURE_2D, texture);

        glBindVertexArray(quadVAO);
        glDrawArrays(GL_TRIANGLES, 0, 6);
        glBindVertexArray(0);

        glfwSwapBuffers(window);
    

    glDeleteVertexArrays(1, &quadVAO);
    glDeleteBuffers(1, &VBO);

    glfwTerminate();

    return EXIT_SUCCESS;

【问题讨论】：

也许您必须通过 glEnable() 启用纹理？

@Beko 不，还是一样。

@Rabbid76 好吧，我不知道。我自己是 OpenGL 的新手，所以感谢您提供的信息。

【参考方案1】：

你必须初始化模型矩阵变量glm::mat4 model。

glm API documentation 指的是The OpenGL Shading Language specification 4.20。

5.4.2 向量和矩阵构造函数

如果向量构造函数有一个标量参数，它用于将构造向量的所有组件初始化为该标量的值。 如果矩阵构造函数只有一个标量参数，则用于初始化矩阵对角线上的所有分量，其余分量初始化为 0.0。

这意味着，单位矩阵可以由单个参数 1.0 初始化：

glm::mat4 model(1.0f);

此外，您的精灵非常小，并且位于左侧的视口（剪辑空间）之外：

像这样更改您的代码：

glm::vec2 position = glm::vec2(10.0f, 10.0f); // 10.0f instead of -10.0f