倒X轴OpenGL

Question

所以我在youtube上看了一个小小的介绍课程，学习OpenGL的基础知识，并学习了制作三角形和简单的相机课等等。我想尝试制作一个体素引擎这么明显我想做的第一件事是一个简单的立方体，我最终可以复制。我的问题是，当我去渲染顶点和三角形时，它们看起来像一个混乱，不像我在立方体类中硬编码的那样。我知道0,0是屏幕的中心; x轴上的1是右边; -1是左边; y轴为1，顶部为-1，底部为-1。然而，当我通过我的顶点和三角形发送到顶点缓冲区时，它似乎做了一些完全不同的事情。对我而言，这很可能是一个非常愚蠢的错误。

Cube::Cube()
{
m_vertices[0] = Vertex(glm::vec3(-0.5, -0.5, 0));
m_vertices[1] = Vertex(glm::vec3(-0.5, 0.5, 0));
m_vertices[2] = Vertex(glm::vec3(0.5, 0.5, 0));
m_vertices[3] = Vertex(glm::vec3(0.5, -0.5, 0));
m_vertices[4] = Vertex(glm::vec3(-0.5, -0.5, 1));
m_vertices[5] = Vertex(glm::vec3(-0.5, 0.5, 1));
m_vertices[6] = Vertex(glm::vec3(0.5, 0.5, 1)); 
m_vertices[7] = Vertex(glm::vec3(0.5, -0.5, 1));

m_triangles[0] = Triangle(0, 1, 2); //Front
//m_triangles[1] = Triangle(0, 2, 3); //Front

//m_triangles[2] = Triangle(1, 5, 6); //Top
//m_triangles[3] = Triangle(1, 6, 2); //Top

//m_triangles[4] = Triangle(3, 5, 4); //Left
//m_triangles[5] = Triangle(3, 5, 4); //Left

//m_triangles[6] = Triangle(3, 2, 7); //Right
//m_triangles[7] = Triangle(3, 3, 7); //Right

//m_triangles[8] = Triangle(7, 6, 4); //Back
//m_triangles[9] = Triangle(5, 6, 7); //Back

//m_triangles[10] = Triangle(0, 4, 7); //Bottom
//m_triangles[11] = Triangle(0, 3, 7); //Bottom
}

void Cube::Render()
{
   Draw(m_vertices, sizeof(m_vertices) / sizeof(m_vertices[0]), m_triangles, (sizeof(m_triangles) / sizeof(m_triangles[0])));
}

绘制函数继承自我的网格类

void Mesh::Draw(Vertex* vertices, unsigned int numVertices, Triangle* triangles, unsigned int numTriangles)
{
//Array of indices
std::vector<unsigned int> indices;
for (int i = 0; i < numTriangles; i++)
{
    indices.push_back(triangles[i].GetTriangle()[0]);
    indices.push_back(triangles[i].GetTriangle()[1]);
    indices.push_back(triangles[i].GetTriangle()[2]);
}

//How many vertices to draw
m_drawCount = indices.size();

//Generate and bind vertex array
glGenVertexArrays(1, &m_vertexArrayObject);
glBindVertexArray(m_vertexArrayObject);

//Generate and bind buffers
glGenBuffers(NUM_BUFFERS, m_vertexArrayBuffers);
glBindBuffer(GL_ARRAY_BUFFER, m_vertexArrayBuffers[POSITION_VB]);
//Write vertex data to the buffer
glBufferData(GL_ARRAY_BUFFER, numVertices * sizeof(vertices[0]), &vertices[0], GL_STATIC_DRAW);

//Only one attribute for the vertex data
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);

glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_vertexArrayBuffers[INDEX_VB]);
//Write vertex data to the buffer
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices[0]) * indices.size(), &indices[0], GL_STATIC_DRAW);

//Unbind vertex array
glBindVertexArray(0);

glBindVertexArray(m_vertexArrayObject);

glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
glDrawElements(GL_TRIANGLES, m_drawCount, GL_UNSIGNED_INT, 0);

glBindVertexArray(0);
}

mesh.h中的顶点和三角形结构

struct Vertex
{
public:
//Constructor
Vertex()
{

}
//Constructor
Vertex(const glm::vec3& pos)
{
    //Set vertex position
    this->m_pos = pos;
}
protected:

private:
//Vertex position
glm::vec3 m_pos;
};

struct Triangle
{
public:
//Constructor
Triangle()
{

}

//Constructor
Triangle(int point1, int point2, int point3)
{
    SetTriangle(point1, point2, point3);
}

int* GetTriangle()
{
    return m_points;
}

void SetTriangle(int point1, int point2, int point3)
{
    m_points[0] = point1;
    m_points[1] = point2;
    m_points[2] = point3;
}
protected:

private:
int m_points[3];
};

相机功能

Camera::Camera(const glm::vec3 pos, float fov, float aspect, float zNear, float zFar)
{
m_perspectiveMatrix = glm::perspective(fov, aspect, zNear, zFar);
m_pos = pos;
m_forward = glm::vec3(0, 0, 1);
m_up = glm::vec3(0, 1, 0);
}

glm::mat4 Camera::GetViewProjection() const
{
 return m_perspectiveMatrix * glm::lookAt(m_pos, m_pos + m_forward, m_up);
}

请注意，在立方体构造函数中，我只创建一个应该在左下角，左上角，右上角的三角形，但这就是结果：

另一个注意事项是我的相机旋转似乎也已关闭。更改y旋转实际上是在x轴上旋转，更改x旋转在y轴上旋转。

此外，如果有人有更好的方法来创建和渲染立方体，我将不胜感激。一旦我能做到这一点，我很可能会研究一下letmakeavoxelengine教程。

编辑：感觉x和y轴是倒置的。我可以反驳我的所有功能来对抗这种情况，但这种方法很糟糕，而且它仍然没有解决可能在以后引起更多麻烦的潜在问题。

Edit2：Transform.h

#pragma once
#include <glm\glm.hpp>
#include <glm\gtx\transform.hpp>
#include "Camera.h"

struct Transform
{
public:
//Constructor
Transform(const glm::vec3& pos = glm::vec3(), const glm::vec3& rot = glm::vec3(), const glm::vec3& scale = glm::vec3(1.0f, 1.0f, 1.0f))
{
    this->m_pos = pos;
    this->m_rot = rot;
    this->m_scale = scale;
}

//Get the model matrix
inline glm::mat4 GetModelMatrix() const
{
    //Create all the transform matrices

    //Position matrix
    glm::mat4 posMatrix = glm::translate(m_pos);
    //Scale matrix
    glm::mat4 scaleMatrix = glm::scale(m_scale);
    //Rotation matrix X
    glm::mat4 rotXMatrix = glm::rotate(m_rot.x, glm::vec3(1.0f, 0.0f, 0.0f));
    //Rotation matrix Y
    glm::mat4 rotYMatrix = glm::rotate(m_rot.y, glm::vec3(0.0f, 1.0f, 0.0f));
    //Rotation matrix Z
    glm::mat4 rotZMatrix = glm::rotate(m_rot.z, glm::vec3(0.0f, 0.0f, 1.0f));
    //Combined rotation matrix
    glm::mat4 rotMatrix = rotXMatrix * rotYMatrix * rotZMatrix;

    return posMatrix * rotMatrix * scaleMatrix;
}

inline glm::mat4 GetMVP(const Camera& camera) const
{
    glm::mat4 ViewProjection = camera.GetViewProjection();
    glm::mat4 ModelMatrix = GetModelMatrix();

    return ViewProjection * ModelMatrix;//camera.GetViewProjection() * GetModel();
}

//Get position
inline glm::vec3* GetPosition() { return &m_pos; }
//Get rotation
inline glm::vec3* GetRotation() { return &m_rot; }
//Get scale
inline glm::vec3* GetScale() { return &m_scale; }

//Set Position
inline void SetPosition(const glm::vec3& pos) { this->m_pos = pos; }
//Set Rotation
inline void SetRotation(const glm::vec3& rot) { this->m_rot = rot; }
//Set Scale
inline void SetScale(const glm::vec3& scale) { this->m_scale = scale; }

private:
//Transform position
glm::vec3 m_pos;
//Transform rotation
glm::vec3 m_rot;
//Transform scale
glm::vec3 m_scale;
};

main.cpp中的Cube，Transform和Camera调用：

Cube cube;
Transform transform;
Camera camera(glm::vec3(0.0f, 0.0f, -3.0f), 70.0f, (float)display.GetWidth()/(float)display.GetHeight(), 0.01f, 100.0f);

Edit3：在X轴上100％反转。新的cube.cpp代码：

m_vertices[0] = Vertex(glm::vec3(-0.5, -0.5, 0)); //BottomLeftFront
m_vertices[1] = Vertex(glm::vec3(-0.5, 0.5, 0)); //TopLeftFront
m_vertices[2] = Vertex(glm::vec3(0.5, 0.5, 0)); //TopRightFront
m_vertices[3] = Vertex(glm::vec3(0.5, -0.5, 0)); //BottomRightFront
m_vertices[4] = Vertex(glm::vec3(-0.5, -0.5, 1)); //BottomLeftBack
m_vertices[5] = Vertex(glm::vec3(-0.5, 0.5, 1)); //TopLeftBack
m_vertices[6] = Vertex(glm::vec3(0.5, 0.5, 1)); //TopRightBack
m_vertices[7] = Vertex(glm::vec3(0.5, -0.5, 1)); //BottomRightBack

m_triangles[0] = Triangle(0, 1, 2); //Front
m_triangles[1] = Triangle(0, 2, 3); //Front

//m_triangles[2] = Triangle(1, 5, 6); //Top
//m_triangles[3] = Triangle(1, 6, 2); //Top

m_triangles[4] = Triangle(3, 5, 4); //Left //BottomLeftFront, TopRightBack, BottomRightBack
//m_triangles[5] = Triangle(3, 5, 4); //Left

//m_triangles[6] = Triangle(3, 2, 7); //Right
//m_triangles[7] = Triangle(3, 3, 7); //Right

//m_triangles[8] = Triangle(7, 6, 4); //Back
//m_triangles[9] = Triangle(5, 6, 7); //Back

//m_triangles[10] = Triangle(0, 4, 7); //Bottom
//m_triangles[11] = Triangle(0, 3, 7); //Bottom

我在新三角形旁边放了一条评论，告诉你实际产生的三角形点是什么。根据代码，我设置的三角形应该是BottomRightFront，TopLeftBack，BottomLeftBack。我还会添加它的外观截图。

Answer 1

您对X和Y轴的描述听起来是正确的，但Z轴似乎是相反的。例如，在您发布的代码中，有一个变量m_forward，其值为（0,0,1）; 可以是正确的，但我通常会将这个方向称为“向后”。

传统上，OpenGL程序使用右手坐标系，因此如果X指向右，Y指向上，则Z指向屏幕外，朝向眼睛。如果你记住这一点并检查你的代码，检查每个位置和方向向量的Z分量的符号，你应该找到错误。祝你好运！