创建索引和 GL_TRIANGLES 表面（仅适用于顶点数据）

Posted 2023-02-22

【中文标题】创建索引和 GL_TRIANGLES 表面（仅适用于顶点数据）

【英文标题】：creating indexes and GL_TRIANGLES surface (only works with vertices data)

【发布时间】：2013-10-15 02:44:59

【问题描述】：

我遇到了一个我无法解决的问题：

尝试绘制由正方形网格（即两个三角形）形成的表面。 当我只使用顶点数据和绘图时一切正常：

//m_totalVertices = m_rows*(m_cols *6)  -> m_rows and m_cols are the quantity of columns and rows that build the surface
glDrawArrays(GL_TRIANGLES, 0, m_totalVertices);

例如：

//first Quad
Vertex[0] = -15,5;
Vertex[1] = -5,5;
Vertex[2] = -5,-5;
Vertex[3] = -5,-5;
Vertex[4] = -15,-5;
Vertex[5] = -15,5;
//second Quad
Vertex[0] = -5,5;
Vertex[1] = 5,5;
Vertex[2] = 5,-5;
Vertex[3] = 5,-5;
Vertex[4] = -5,-5;
Vertex[5] = -5,5;
//third Quad
Vertex[0] = 5,5;
Vertex[1] = 15,5;
Vertex[2] = 15,-5;
Vertex[3] = 15,-5;
Vertex[4] = 5,-5;
Vertex[5] = 5,5;

结果：

作为优化问题，我想使用“索引”来减少顶点数据的数量，但表面会变形：

要绘制它，我使用下一个函数：

//m_totalVertices = m_rows*(m_cols *6)  -> m_rows and m_cols are the quantity of columns and rows that build the surface
glDrawElements(GL_TRIANGLES, m_totalVertices, GL_UNSIGNED_INT, 0);

例如：

//first Quad
indices[0] = 0;
indices[1] = 1;
indices[2] = 2;
indices[3] = 2;
indices[4] = 3;
indices[5] = 0;
//second Quad
indices[6] = 1;
indices[7] = 4;
indices[8] = 5;
indices[9] = 5;
indices[10] = 2;
indices[11] = 1;
//third Quad
indices[12] = 4;
indices[13] = 6;
indices[14] = 7;
indices[15] = 7;
indices[16] = 5;
indices[17] = 4;

//first Quad
Vertex[0] = -15,5;
Vertex[1] = -5,5;
Vertex[2] = -5,-5;
Vertex[3] = -15,-5;
//second Quad
Vertex[0] = -5,5;
Vertex[1] = 5,5;
Vertex[2] = 5,-5;
Vertex[3] = -5,-5;
//third Quad
Vertex[0] = 5,5;
Vertex[1] = 15,5;
Vertex[2] = 15,-5;
Vertex[3] = 5,-5;

结果：

这是仅使用顶点数据（无索引）生成表面的类的代码 [WORKS PERFECT]：

 #include "plane.h"
#include "matrix.h"
#include "glslshader.h"
#include "texture.h"

plane::plane(GLuint cols, GLuint rows,GLuint segmentSize, mixedColors color, CTexture* texture, GLshort textureMode) :
m_matrix(0),
m_shader(0),
m_cols(cols),
m_rows(rows),
m_segmentSize(segmentSize),
m_selectedColor(color),
m_texture(texture),
m_textureMode(textureMode),
m_totalVertices(rows*(cols*6))

    //matrix handler
    m_matrix = matrix::getInstance();

    //check that variables are > 1
    if(m_cols < 1)m_cols = 1;
    if(m_rows < 1)m_rows = 1;

    // generate a VAO 
    glGenVertexArrays(1, &m_uiVAO);

    vbo.createVBO();



plane::~plane()

    delete m_shader;
    vbo.releaseVBO();

    glDeleteVertexArrays(1, &m_uiVAO);



bool plane::init()

    //load the shaders
    if(m_texture == NULL)
    
        m_shader = new GLSLProgram("data/shaders/shader-primitives.vert", "data/shaders/shader-primitives.frag");
    
    else//if primitive use texture...
        
            m_shader = new GLSLProgram("data/shaders/shader-texture.vert", "data/shaders/shader-texture.frag");
        

    if (!m_shader->initialize())
    
        cout << "Los shaders de las primitivas no pudieron ser incializados\n";
        return false;
    
    m_shader->linkProgram();

    //number of QUAD vertex
    const GLshort QUAD_ELEMENTS = 6;

    GLuint r,c,q,x;

    //bind VBO
    vbo.bindVBO();

    //set the start where you draw the first square of the plane
    // so that everything is centered
    GLfloat initX,initY;
    initX = initY = 0.0f;

    //displacement of each QUAD in X and Y axis.
    const float MODULE = 0.2f;


    //find the init value of X (the start value where you draw the first QUAD)
    if(m_cols > 1)
    
        initX = (float)((m_cols*MODULE/2.0f))-0.1f;
    
    //find the init value of y (the start value where you draw the first QUAD)
    if(m_rows > 1)
    
        initY = (float)((m_rows*MODULE/2.0f))-0.1f;
    



    //QUAD vertex data
    vector3f quad[QUAD_ELEMENTS];
    quad[0] = vector3f(-0.1f,0.1f,0.0f); quad[1] = vector3f(0.1f,0.1f,0.0f);
    quad[2] = vector3f(0.1f,-0.1f,0.0f); quad[3] = vector3f(0.1f,-0.1f,0.0f);
    quad[4] = vector3f(-0.1f,-0.1f,0.0f); quad[5] = vector3f(-0.1f,0.1f,0.0f);



    x=0;
    //put QUAD vertex in the "init position"
    for(x=0;x<QUAD_ELEMENTS;++x)
    
        quad[x].x = quad[x].x + (-initX);
        quad[x].y = quad[x].y + initY;
    


    //store de actual Y value of row (Y axis)
    GLfloat newRow = 0.0f;
    //store de actual X value of column (X axis)
    GLfloat newColumn = 0.0f;


    GLuint colorCounter = 0;


    for(r=0;r<m_rows;++r)
    
        //reset newColumn variable to 0.0f for each new column
        newColumn = 0.0f;

        //for each column
        for(c=0;c<m_cols;++c)
        
            //copy QUAD vertex data in new array
            vector3f quadCopy[QUAD_ELEMENTS] = quad;
            //for each column, move 0.1f to right
            for(q=0;q<QUAD_ELEMENTS;++q)
            
                //move right one MODULE (in x axis)
                quadCopy[q].x = float(quadCopy[q].x + newColumn);
                //move down one MODULE (in Y axis)
                quadCopy[q].y = float(quadCopy[q].y + newRow);
                //add vertex data and color to de vbo
                vector3f resizedVertex = vector3f(quadCopy[q].x*m_segmentSize,quadCopy[q].y*m_segmentSize,quadCopy[q].z);
                vbo.addData(&resizedVertex,sizeof(vector3f));
                //every 4 laps reset colorCounter to 0;

                cout << "Vertex["<< q << "] = "<< resizedVertex.x << "," << resizedVertex.y << ";\n";
                if(colorCounter == 3)colorCounter = 0;
                vbo.addData(&color4f(m_selectedColor.color[colorCounter].r,m_selectedColor.color[colorCounter].g,m_selectedColor.color[colorCounter].b,m_selectedColor.color[colorCounter].a),sizeof(color4f));


                ++colorCounter;
            

            //for each column, move right 0.1f
            newColumn += MODULE;

        

        newRow -= MODULE;
    


    //bind VAO
    glBindVertexArray(m_uiVAO);
    //bind VBO
    vbo.bindVBO();
    vbo.uploadDataToGPU(GL_STATIC_DRAW);

    glEnableVertexAttribArray(1);
    glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, sizeof(vector3f)+sizeof(color4f), (void*)sizeof(vector3f));

    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(vector3f)+sizeof(color4f), 0);

    return true;



void plane::render()

    //bind shader
    m_shader->bindShader();
    //send projection matrix to shader
    m_shader->sendUniform4x4("projectionMatrix", glm::value_ptr(*m_matrix->getProjectionMatrix()));


    //matrix transformations
    m_matrix->loadIdentity();
    m_matrix->scale(vector3f(m_scale,m_scale,m_scale));
    m_matrix->translate(m_pos);
    m_matrix->rotateX(m_orientation.x);
    m_matrix->rotateY(m_orientation.y);
    m_matrix->rotateY(m_orientation.z);

    //sendtransformation matrix  (modelview)
    m_shader->sendUniform4x4("modelViewMatrix", glm::value_ptr(m_matrix->getModelViewMatrix()));

    //bind VAO
    glBindVertexArray(m_uiVAO);

    glDrawArrays(GL_TRIANGLES, 0, m_totalVertices);

这是生成具有顶点数据和索引的表面的类（修改）的代码 [DONT WORK]：

#include "plane.h"
#include "matrix.h"
#include "glslshader.h"
#include "texture.h"

plane::plane(GLuint cols, GLuint rows,GLuint segmentSize, mixedColors color, CTexture* texture, GLshort textureMode) :
m_matrix(0),
m_shader(0),
m_cols(cols),
m_rows(rows),
m_segmentSize(segmentSize),
m_selectedColor(color),
m_texture(texture),
m_textureMode(textureMode),
m_totalVertices(rows*(cols*6))

    //matrix handler
    m_matrix = matrix::getInstance();

    //check that variables are > 1
    if(m_cols < 1)m_cols = 1;
    if(m_rows < 1)m_rows = 1;

    // generate a VAO 
    glGenVertexArrays(1, &m_uiVAO);

    vbo.createVBO();
    vboIndices.createVBO();


plane::~plane()

    delete m_shader;
    vbo.releaseVBO();
    vboIndices.releaseVBO();
    glDeleteVertexArrays(1, &m_uiVAO);



bool plane::init()

    //load the shaders
    if(m_texture == NULL)
    
        m_shader = new GLSLProgram("data/shaders/shader-primitives.vert", "data/shaders/shader-primitives.frag");
    
    else//if primitive use texture...
        
            m_shader = new GLSLProgram("data/shaders/shader-texture.vert", "data/shaders/shader-texture.frag");
        

    if (!m_shader->initialize())
    
        cout << "Los shaders de las primitivas no pudieron ser incializados\n";
        return false;
    
    m_shader->linkProgram();

    //number of QUAD vertex
    const GLshort QUAD_ELEMENTS = 4;

    GLuint r,c,q,x;

    //---------------------------------------------------------------------------
    //bind VBO
    vboIndices.bindVBO(GL_ELEMENT_ARRAY_BUFFER);
    //base indices that are used to generate dynamic indices to all vertex data

    GLuint  baseIndices[6] = 0,1,2,2,3,0;
    GLshort indicesCounter = 0;



    cout << "indices==========================================\n";



    for(x=0;x<m_totalVertices;++x)
    

        if(indicesCounter == 6)
        
            cout << "new pack of indices = " << x << "\n";

            baseIndices[0] = baseIndices[1];
            if(x > 6)baseIndices[1] += 2;elseif(x == 6)baseIndices[1] += 3;
            baseIndices[2] = (baseIndices[1]+1);
            baseIndices[3] = baseIndices[2];
            baseIndices[4] = baseIndices[0]+1;
            baseIndices[5] = baseIndices[0];
            indicesCounter = 0;
        

        vboIndices.addData(&baseIndices[indicesCounter],sizeof(GLuint ));
        cout << "indices["<<x<<"] = " << baseIndices[indicesCounter] << "\n";

        ++indicesCounter;
    
    //-------------------------------------------------------------------------------


    //bind VBO
    vbo.bindVBO();

    //set the start where you draw the first square of the plane
    // so that everything is centered
    GLfloat initX,initY;
    initX = initY = 0.0f;

    //displacement of each QUAD in X and Y axis.
    const float MODULE = 0.2f;


    //find the init value of X (the start value where you draw the first QUAD)
    if(m_cols > 1)
    
        initX = (float)((m_cols*MODULE/2.0f))-0.1f;
    
    //find the init value of y (the start value where you draw the first QUAD)
    if(m_rows > 1)
    
        initY = (float)((m_rows*MODULE/2.0f))-0.1f;
    



    //QUAD vertex data
    vector3f quad[QUAD_ELEMENTS];

    quad[0] = vector3f(-0.1f,0.1f,0.0f); quad[1] = vector3f(0.1f,0.1f,0.0f);
    quad[2] = vector3f(0.1f,-0.1f,0.0f); quad[3] = vector3f(-0.1f,-0.1f,0.0f);


     //put QUAD vertex in the "init position"
    for(x=0;x<QUAD_ELEMENTS;++x)
    
        quad[x].x = quad[x].x + (-initX);
        quad[x].y = quad[x].y + initY;
    


    //store de actual Y value of row (Y axis)
    GLfloat newRow = 0.0f;
    //store de actual X value of column (X axis)
    GLfloat newColumn = 0.0f;


    GLuint colorCounter = 0;

    for(r=0;r<m_rows;++r)
    
        //reset newColumn variable to 0.0f for each new column
        newColumn = 0.0f;

        //for each column
        for(c=0;c<m_cols;++c)
        
            //copy QUAD vertex data in new array
            vector3f quadCopy[QUAD_ELEMENTS] = quad;
            //for each column, move 0.1f to right
            for(q=0;q<QUAD_ELEMENTS;++q)
            
                //move right one MODULE (in x axis)
                quadCopy[q].x = float(quadCopy[q].x + newColumn);
                //move down one MODULE (in Y axis)
                quadCopy[q].y = float(quadCopy[q].y + newRow);
                //add vertex data and color to de vbo
                vector3f resizedVertex = vector3f(quadCopy[q].x*m_segmentSize,quadCopy[q].y*m_segmentSize,quadCopy[q].z);
                vbo.addData(&resizedVertex,sizeof(vector3f));
                //every 4 laps reset colorCounter to 0;

                cout << "Vertex["<< q << "] = "<< resizedVertex.x << "," << resizedVertex.y << ";\n";
                if(colorCounter == 3)colorCounter = 0;
                vbo.addData(&color4f(m_selectedColor.color[colorCounter].r,m_selectedColor.color[colorCounter].g,m_selectedColor.color[colorCounter].b,m_selectedColor.color[colorCounter].a),sizeof(color4f));


                ++colorCounter;
            

            //for each column, move right 0.1f
            newColumn += MODULE;

        

        newRow -= MODULE;
    


    //bind VAO
    glBindVertexArray(m_uiVAO);
    //bind VBO
    vbo.bindVBO();
    vbo.uploadDataToGPU(GL_STATIC_DRAW);

    glEnableVertexAttribArray(1);
    glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, sizeof(vector3f)+sizeof(color4f), (void*)sizeof(vector3f));

    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(vector3f)+sizeof(color4f), 0);


    //load indices data in VBO
    vboIndices.bindVBO(GL_ELEMENT_ARRAY_BUFFER);
    vboIndices.uploadDataToGPU(GL_STATIC_DRAW);

    return true;



void plane::render()

    //bind shader
    m_shader->bindShader();
    //send projection matrix to shader
    m_shader->sendUniform4x4("projectionMatrix", glm::value_ptr(*m_matrix->getProjectionMatrix()));


    //matrix transformations
    m_matrix->loadIdentity();
    m_matrix->scale(vector3f(m_scale,m_scale,m_scale));
    m_matrix->translate(m_pos);
    m_matrix->rotateX(m_orientation.x);
    m_matrix->rotateY(m_orientation.y);
    m_matrix->rotateY(m_orientation.z);

    /sendtransformation matrix  (modelview)
    m_shader->sendUniform4x4("modelViewMatrix", glm::value_ptr(m_matrix->getModelViewMatrix()));

    //bind VAO
    glBindVertexArray(m_uiVAO);

    glDrawElements(GL_TRIANGLES, m_totalVertices, GL_UNSIGNED_INT, 0);

这是处理VBO的类的代码[这个工作完美，只是放在这里让你了解这些方法是什么]：

#include "common_header.h"

#include "vertexBufferObject.h"

CVertexBufferObject::CVertexBufferObject()

    bDataUploaded = false;


/*-----------------------------------------------

Name:       createVBO

Params: a_iSize - initial size of buffer

Result: Creates vertex buffer object.

/*---------------------------------------------*/

void CVertexBufferObject::createVBO(int a_iSize)

    //obtiene el ID del VBO
    glGenBuffers(1, &uiBuffer);
    //reserva espacio para los datos que va a alojar
    data.reserve(a_iSize);
    //setea el tamaño
    iSize = a_iSize;


/*-----------------------------------------------

Name:       releaseVBO

Params: none

Result: Releases VBO and frees all memory.

/*---------------------------------------------*/

void CVertexBufferObject::releaseVBO()

    //elimina el ID obtenido
    glDeleteBuffers(1, &uiBuffer);
    bDataUploaded = false;
    //libera todos los datos almacenados
    data.clear();


/*-----------------------------------------------

Name:       mapBufferToMemory

Params: iUsageHint - GL_READ_ONLY, GL_WRITE_ONLY...

Result: Maps whole buffer data to memory and
            returns pointer to data.

/*---------------------------------------------*/

void* CVertexBufferObject::mapBufferToMemory(int iUsageHint)

    if(!bDataUploaded)return 0;
    void* ptrRes = glMapBuffer(iBufferType, iUsageHint);
    return ptrRes;


/*-----------------------------------------------

Name:       mapSubBufferToMemory

Params: iUsageHint - GL_READ_ONLY, GL_WRITE_ONLY...
            uiOffset - data offset (from where should
                            data be mapped).
            uiLength - length of data

Result: Maps specified part of buffer to memory.

/*---------------------------------------------*/

void* CVertexBufferObject::mapSubBufferToMemory(int iUsageHint, unsigned int uiOffset, unsigned int uiLength)

    if(!bDataUploaded)return 0;
    void* ptrRes = glMapBufferRange(iBufferType, uiOffset, uiLength, iUsageHint);
    return ptrRes;


/*-----------------------------------------------

Name:       unmapBuffer

Params: none

Result: Unmaps previously mapped buffer.

/*---------------------------------------------*/

void CVertexBufferObject::unmapBuffer()

    glUnmapBuffer(iBufferType);


/*-----------------------------------------------

Name:       bindVBOiDrawingHint)

    glBufferData(iBufferType, data.size(), &data[0], iDrawingHint);
    bDataUploaded = true;


Params: a_iBufferType - buffer type (GL_ARRAY_BUFFER, ...)

Result: Binds this VBO.

/*---------------------------------------------*/

void CVertexBufferObject::bindVBO(int a_iBufferType)

    iBufferType = a_iBufferType;
    glBindBuffer(iBufferType, uiBuffer);


/*-----------------------------------------------

Name:       uploadDataToGPU

Params: iUsageHint - GL_STATIC_DRAW, GL_DYNAMIC_DRAW...

Result: Sends data to GPU.

/*---------------------------------------------*/

void CVertexBufferObject::uploadDataToGPU(int iDrawingHint)

    glBufferData(iBufferType, data.size(), &data[0], iDrawingHint);
    bDataUploaded = true;
    data.clear();


/*-----------------------------------------------

Name:       addData

Params: ptrData - pointer to arbitrary data
            uiDataSize - data size in chars

Result: Adds arbitrary data to VBO.

/*---------------------------------------------*/

void CVertexBufferObject::addData(void* ptrData, unsigned int uiDataSize)

    data.insert(data.end(), (char*)ptrData, (char*)ptrData+uiDataSize);


/*-----------------------------------------------

Name:       getDataPointer

Params: none

Result: Returns data pointer (only before uplading).

/*---------------------------------------------*/

void* CVertexBufferObject::getDataPointer()

    if(bDataUploaded)return 0;
    return (void*)data[0];


/*-----------------------------------------------

Name:       getBuffer

Params: none

Result: Returns VBO ID.

/*---------------------------------------------*/

unsigned int CVertexBufferObject::getBuffer()

    return uiBuffer;

【问题讨论】：

您的索引代码很大而且很难阅读。您能否详细说明如何填写 baseIndices 变量？看起来问题就在那里。这一切对我来说似乎过于复杂，而且我（可能还有这里的许多其他人）不能很好地阅读西班牙语。

谢谢！我翻译了所有的 cmets，以便更好地理解它们。无论如何，为了避免阅读所有代码，我将代码的输出放在上面，请检查我在“部分”->“例如”上面的文本中提到的内容，这是输出，图像是结果。

有什么想法吗？我迷路了..我不知道为什么索引不能正确绘制表面..

我想我已经明白了。您的索引确实是错误的，您需要填写不同的数字。此外，当调用“glDrawElements(GL_TRIANGLES, m_totalVertices, GL_UNSIGNED_INT, 0);”时您应该始终使用索引数量而不是顶点数量。等待回答

【参考方案1】：

如果没有更多信息，我无法 100% 确定，但无论如何：

正确的索引数组应该是这样的： 0,1,2,2,3,0 , 4,5,6,6,7,4 , 8,9,10,10,11,8。

这是因为您使用索引就像没有重复的顶点一样，但根据输出，您可以 :)。或者，如果您想使用更少的空间，请考虑使用 GL_QUADS 而不是 GL_TRIANGLES，这样您只需为每个四边形指定 4 个索引。

如果您想修复顶点，请仅将顶点 0、1、2、3、5、6、9、10 提交到浮点缓冲区，不要修改索引。

【讨论】：

谢谢！你说的对！ :D 索引应该是： 0,1,2,2,3,0 , 4,5,6,6,7,4 , 8,9,10,10,11,8 以这种方式生成它们，一切正常:) 感谢您的提示并感谢所有人的帮助。

我有一个新的疑问，我为顶点创建了两个 VBO，一个包括纹理，另一个用于索引。事实是纹理，虽然它们被正确映射，但没有显示，或者它这样做是错误的。对于每个四边形，我应用以下纹理： texcoords [0] = texCoord (0.0,1.0); texcoords [1] = texCoord (1.0,1.0); texcoords [2] = texCoord (1.0,0.0); texcoords [3] = texCoord (0.0,0.0);

考虑到“索引VBO”包含6个点来表示QUAD的四个顶点，在“顶点VBO”中只添加四个顶点，每个顶点一个纹理坐标。

忘了最后一件事，这已经解决了，问题是生成纹理坐标，现在可以了！谢谢大家。问题已解决，如果有人告诉我如何将其置于“已解决”状态，我会这样做:) 祝你好运！

没问题！您已将我的答案标记为已接受，因此现在已“解决”:)，您无需执行任何其他操作。