为什么精灵不能在 OpenGL 中渲染?

问题描述

我正在尝试在 OpenGL 中渲染一个 2D(屏幕协调)精灵.然而，当我编译它时，它没有出现.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(我怀疑这是导致问题的原因，这就是混淆的开始！！)

I am trying to render a 2D(Screen coordinated) sprite in OpenGL. Yet, when I compile it, it does not show up. I see that the code is fine (There are not even any shader compilation errors nor any other errors). I also have also the matrices set up(which I doubt is causing the problem, and that's where starts the CONFUSION!!)

顺便说一下，这里是源代码(没有调试，简短一点):-

Here is the source code, by the way(without debugging, to make it short):-

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
"
    "layout(location = 0) in vec4 vertex;
"
    "out vec2 TexCoords;
"
    "uniform mat4 model;
"
    "uniform mat4 projection;
"
    "void main()
"
    "{
"
    "TexCoords = vertex.zw;
"
    "gl_Position = projection * model * vec4(vertex.xy, 0.0, 1.0);
"
    "}";

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

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;
}

推荐答案

你必须初始化模型矩阵变量glm::mat4 model.

You have to initialize the model matrix variable glm::mat4 model.

glm API 文档 指的是 OpenGL 着色语言规范 4.20.

5.4.2 向量和矩阵构造函数

如果向量构造函数只有一个标量参数，则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，它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.

If there is a single scalar parameter to a vector constructor, it is used to initialize all components of the constructed vector to that scalar’s value. If there is a single scalar parameter to a matrix constructor, it is used to initialize all the components on the matrix’s diagonal, with the remaining components initialized to 0.0.

这意味着，可以通过单个参数 1.0 来初始化单位矩阵:

This means, that an identity matrix can be initialized by the single parameter 1.0:

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:

Further your sprite is very small and it is out of the viewport (clip space) at the left side:

像这样改变你的代码:

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

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