平移变换使三角形消失？

Question

这个 OpenGL 代码应该渲染一个在 X 轴上来回移动的三角形：

#include <stdio.h>
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <string.h>
#include <cmath>
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>

// Window dimensions
const GLint WIDTH = 800, HEIGHT = 600;

GLuint VAO, VBO, shader, uniformModel;

bool direction = true;
float triOffest = 0.0f;
float triMaxOffset = 0.7f;
float triIncrement = 0.0005f;

// Vertex Shader
static const char* vShader = "                                          \n\
#version 330                                                            \n\
                                                                        \n\
layout (location = 0) in vec3 pos;                                      \n\
                                                                        \n\
uniform mat4 model;                                                     \n\
                                                                        \n\
void main()                                                             \n\
{                                                                       \n\
    gl_Position = model * vec4(0.4 * pos.x, 0.4 * pos.y, pos.z, 1.0);   \n\
}";

// Fragment Shader
static const char* fShader = "                          \n\
#version 330                                            \n\
                                                        \n\
out vec4 colour;                                        \n\
                                                        \n\
void main()                                             \n\
{                                                       \n\
    colour = vec4(1.0, 0.0, 0.0, 1.0);                  \n\
}";



void CreateTriangle()
{
    GLfloat vertices[] = {
        -1.0f, -1.0f, 0.0f,
        1.0f, -1.0f, 0.0f,
        0.0f, 1.0f, 0.0f
    };

    glGenVertexArrays(1, &VAO);
    glBindVertexArray(VAO);

    glGenBuffers(1, &VBO);
    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
    glEnableVertexAttribArray(0);

    glBindBuffer(GL_ARRAY_BUFFER, 0);

    glBindVertexArray(0);
}

void AddShader(GLuint theProgram, const char* shaderCode, GLenum shaderType)
{
    GLuint theShader = glCreateShader(shaderType);

    const GLchar* theCode[1];
    theCode[0] = shaderCode;

    GLint codeLength[1];
    codeLength[0] = strlen(shaderCode);

    glShaderSource(theShader, 1, theCode, codeLength);
    glCompileShader(theShader);

    GLint result = 0;
    GLchar eLog[1024] = { 0 };

    glGetShaderiv(theShader, GL_COMPILE_STATUS, &result);
    if (!result)
    {
        glGetShaderInfoLog(theShader, sizeof(eLog), NULL, eLog);
        printf("Error compiling %d shader: '%s'\n", shaderType, eLog);
        return;
    }

    glAttachShader(theProgram, theShader);
}

void CompileShaders()
{
    shader = glCreateProgram();

    if (!shader)
    {
        printf("Error creating shader program!\n");
        return;
    }

    AddShader(shader, vShader, GL_VERTEX_SHADER);
    AddShader(shader, fShader, GL_FRAGMENT_SHADER);

    GLint result = 0;
    GLchar eLog[1024] = { 0 };

    glLinkProgram(shader);
    glGetProgramiv(shader, GL_LINK_STATUS, &result);

    if (!result)
    {
        glGetProgramInfoLog(shader, sizeof(eLog), NULL, eLog);
        printf("Error linking program: '%s'\n", eLog);
        return;
    }

    glValidateProgram(shader);
    glGetProgramiv(shader, GL_VALIDATE_STATUS, &result);

    if (!result)
    {
        glGetProgramInfoLog(shader, sizeof(eLog), NULL, eLog);
        printf("Error validating program: '%s'\n", eLog);
        return;
    }

    uniformModel = glGetUniformLocation(shader, "model");
}

int main()
{
    // Initialise GLFW
    if (!glfwInit())
    {
        printf("GLFW initialisation failed!");
        glfwTerminate();
        return 1;
    }

    // Setup GLFW window properties
    // OpenGL version
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);

    // core profile = No backwards Compatibility
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);

    GLFWwindow* mainWindow = glfwCreateWindow(WIDTH, HEIGHT, "Test Window", NULL, NULL);

    if (!mainWindow)
    {
        printf("GLFW window creation failed!");
        glfwTerminate();
        return 1;
    }

    // Get buffer size information
    int bufferWidth, bufferHeight;
    glfwGetFramebufferSize(mainWindow, &bufferWidth, &bufferHeight);

    // Set context for GLEW to use
    glfwMakeContextCurrent(mainWindow);

    // Allow modern extension features
    glewExperimental = GL_TRUE;

    if (glewInit() != GLEW_OK)
    {
        printf("GLEW initialisation failed!");
        glfwDestroyWindow(mainWindow);
        glfwTerminate();
        return 1;
    }

    // Setup viewport size
    glViewport(0, 0, bufferWidth, bufferHeight);

    CreateTriangle();
    CompileShaders();

    // Loop unitil window closed
    while (!glfwWindowShouldClose(mainWindow))
    {
        // Get + Handle user input events
        glfwPollEvents();

        if (direction)
        {
            triOffest += triIncrement;
        }
        else
        {
            triOffest -= triIncrement;
        }

        if (abs(triOffest) >= triMaxOffset)
        {
            direction = !direction;
        }

        // Clear window
        glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);

        glUseProgram(shader);

        glm::mat4 model;
        model = glm::translate(model, glm::vec3(triOffest, 0.0f, 0.0f));

        glUniformMatrix4fv(uniformModel, 1, GL_FALSE, glm::value_ptr(model));

        glBindVertexArray(VAO);
        glDrawArrays(GL_TRIANGLES, 0, 3);
        glBindVertexArray(0);

        glUseProgram(0);

        glfwSwapBuffers(mainWindow);
    }
    return 0;
}

但是，在我运行代码后，我只看到一个空白屏幕。（在将平移变换矩阵与顶点着色器中的顶点位置相乘之前，三角形确实呈现了）。应用转换模型后，三角形似乎消失了。

谁能帮我找出问题所在？

Answer 1

正如@Botje 建议的那样，我只需要将mat4 模型初始化为glm::mat4 model(1.0); 在 main() 里面完成了.. 问题解决了。