未绘制三角形。 C++/GLEW/SDL [关闭]

Posted 2023-02-22

【中文标题】未绘制三角形。 C++/GLEW/SDL [关闭]

【英文标题】：Triangle not being drawn. C++/GLEW/SDL [closed]

【发布时间】：2019-08-29 17:07:16

【问题描述】：

我正在尝试创建一个在屏幕上绘制红色三角形的程序，我使用 GLFW 而不是 SDL 并且不使用类成功地做到了这一点。 但是，在 SDL 中执行此操作并使用类时，它似乎没有绘制三角形，但构建成功并返回 0。

我已经仔细扫描了我的代码，但仍然找不到解决方案。

是不是因为我根本无法在这种编程中使用类（我对此表示怀疑）？

main.cpp

#include <iostream>
#include <GL/glew.h>
#define SDL_MAIN_HANDLED
#include <SDL/SDL.h>
#include <SDL/SDL_opengl.h>

#include "Shader.h"
#include "Shape.h"

using namespace std;

const GLint WIDTH = 800;
const GLint HEIGHT = 600;

GLuint VAO, VBO, shader;

int main() 
    if (SDL_Init(SDL_INIT_VIDEO) < 0) 
        cout << "Error: Failed to initialize SDL!" << endl;
        return 1;
    
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 3);
    SDL_Window* mainWindow = SDL_CreateWindow("My Game", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, WIDTH, HEIGHT, SDL_WINDOW_OPENGL);
    if (mainWindow == nullptr) 
        cout << "Error: Failed to create window [mainWindow]" << endl;
        return 1;
    
    SDL_GLContext context = SDL_GL_CreateContext(mainWindow);
    glewExperimental = GL_TRUE;
    if (glewInit() != GLEW_OK) 
        cout << "Error: Failed to initialize GLEW, OpenGL error." << endl;
        return 1;
    
    Shader cShader;
    Shape shape;

    glViewport(0, 0, WIDTH, HEIGHT);
    shape.CreateTriangle(VAO, VBO);
    cShader.CompileShader(shader);

    SDL_Event windowEvent;
    while (true) 
        if (SDL_PollEvent(&windowEvent)) 
            if (windowEvent.type == SDL_QUIT) 
                break;
            
        
        glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);

        glUseProgram(shader);

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

        glUseProgram(0);
        SDL_GL_SwapWindow(mainWindow);
    
    SDL_GL_DeleteContext(context);
    SDL_DestroyWindow(mainWindow);
    SDL_Quit();
    return 0;

形状.h

#pragma once
#include <GL/glew.h>
class Shape

public:
    void CreateTriangle(GLuint VAO, GLuint VBO);
;

形状.cpp

#include "Shape.h"
#include <GL/glew.h>

void Shape::CreateTriangle(GLuint VAO, GLuint VBO) 
    GLfloat triVertices[] = 
        -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(triVertices), triVertices, GL_STATIC_DRAW);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
    glEnableVertexAttribArray(0);

    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glBindVertexArray(0);

着色器.h

#pragma once
#include <stdio.h>
#include <stdlib.h>
#include <GL/glew.h>
class Shader

public:
    static const char* vShader;
    static const char* fShader;
    void AddShader(const char* shaderCode, GLenum shaderType, GLuint shader);
    void CompileShader(GLuint shader);
;

着色器.cpp

#include "Shader.h"
#include <stdio.h>
#include <stdlib.h>
#include <string>
#include <GL/glew.h>

const char* Shader::vShader = "                                    \n\
#version 330                       ck                                \n\
                                                                   \n\
layout (location = 0) in vec3 pos;                                 \n\
                                                                   \n\
void main()                                                        \n\
                                                                  \n\
     gl_Position = vec4(0.4 * pos.x, 0.4 * pos.y, pos.z, 1.0);     \n\
";

const char* Shader::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 Shader::AddShader(const char* shaderCode, GLenum shaderType, GLuint theProgram) 
    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 the %d shader: %s\n", shaderType, eLog);
        return;
    
    glAttachShader(theProgram, theShader);


void Shader::CompileShader(GLuint shader) 
    shader = glCreateProgram();

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

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

【问题讨论】：

ck 后面的#version 是什么？

无关：声明着色器的更简单方法可能是使用raw string literal..

我看到的一个问题是您将着色器句柄传递给 void CompileShader(GLuint shader); 的值，而不是引用。

@HolyBlackCat 意外错误，但与无法绘制三角形无关，已删除。另外，我必须在每次使用着色器的前面加上 & 吗？

【参考方案1】：

方法的参数

void CreateTriangle(GLuint VAO, GLuint VBO);

void CompileShader(GLuint shader);

按值传递。

如果你想从方法中“取回”创建的对象（值），那么你必须通过引用传递参数：

class Shape

public:
    void CreateTriangle(GLuint &VAO, GLuint &VBO);
;

class Shader

public:

    // ...    

    void CompileShader(GLuint &shader);
;

【讨论】：

谢谢！ @HolyBlackCat 让我参考着色器，但我没有意识到我必须为 VAO 和 VBO 做同样的事情！