c++ - 倒 X 轴 OpenGL

Question

所以我在 youtube 上观看了一些介绍性类(class)以学习 OpenGL 的基础知识并学习了诸如制作三角形和简单相机类等内容。我一直想尝试制作体素引擎，这显然是第一个我想做的是一个我最终可以复制的简单立方体。我的问题是，当我去渲染顶点和三角形时，它们看起来一团糟，这与我在立方体类中硬编码的内容不同。我知道0,0是屏幕的中心； 1在x轴是右边； -1 是左边； y 轴中的 1 是顶部，-1 是底部。然而，当我将顶点和三角形发送到顶点缓冲区时，它似乎在做一些完全不同的事情。这很可能是我的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])));
}

从我的网格类继承的绘制函数

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，我只创建了一个三角形，它应该位于左下角、左上角、右上角，但这是结果:

另一个注意事项是我的相机旋转似乎也关闭了。改变 y 旋转实际上是在 x 轴上旋转，而改变 x 旋转是在 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 letsmakeavoxelengine 教程。

编辑:感觉 x 轴和 y 轴倒置了。我可以反转我所有的函数来解决这个问题，但这是一种绕过它的 hacky 方法，它仍然没有解决潜在的问题，这可能会在以后造成更多麻烦。

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:X 轴 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

我在新三角形旁边添加了注释，告诉您实际生成的三角形点是什么。根据代码，我设置的三角形应该是BottomRightFront、TopLeftBack、BottomLeftBack。我还将添加它的外观截图。

Answer 1

您对 X 轴和 Y 轴的描述听起来不错，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)； 可能是对的，但我通常称那个方向为“向后”。

通常，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。如果您牢记这一点并检查您的代码，检查每个位置和方向 vector 的 Z 分量的符号，您应该会发现错误。祝你好运!