opengl vbo 纹理
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【中文标题】opengl vbo 纹理【英文标题】：opengl vbo texture 【发布时间】：2011-04-03 18:29:11 【问题描述】：我还是 vbo 的初学者，我想渲染一个 collada 模型。从 cae 文件中获取有关顶点、法线和纹理以及顶点、法线和纹理的索引的所有所需信息之后，然后我将它们作为模型对象放在内存中。剩下的就是如何使用带有纹理的 vbo 来渲染这个对象。我设法通过获取顶点和索引成功地渲染对象，然后在 vbo 渲染的情况下应用绘图元素。但是，当我尝试渲染纹理时，使用显示列表渲染它们时会失败，因为我正在通过每个三角形并根据顶点索引和纹理索引正确应用顶点和纹理坐标。那么如何应用在 vbo 中的对象中找到的纹理索引才能正确渲染纹理呢？
这是项目的代码：
#include "bmp.h"
struct mdl_vert
float x,y,z;
;
struct mdl_normal
float x,y,z;
;
struct mdl_texCoord
float u,v;
;
struct mdl_capacity
int vertsSize,indicesSize,normalsSize,texCoordsSize;
;
struct mdl_indices
int *vertIndices;
int *normalIndices;
int *texIndices;
;
class Group
public:
mdl_capacity capacity;
mdl_vert *verts;
mdl_normal *normals;
mdl_texCoord *texCoords;
mdl_indices indices;
char grp_name[64];
Group()
capacity.texCoordsSize=0;
capacity.normalsSize=0;
capacity.indicesSize=0;
capacity.vertsSize=0;
verts=NULL;
normals=NULL;
texCoords=NULL;
indices.vertIndices=NULL;
indices.normalIndices=NULL;
indices.texIndices=NULL;
for(int i=0;i<64;i++)
grp_name[i]='\0';
;
class Model
public:
char tex_name[512];
std::string Name;
Group **groups;
int groupsSize;
#define VBO_BUFFER_SIZE 4
struct GroupObject
GLuint *buffer;
;
class ModelObject
private:
GLuint displayList;
GroupObject *groupBuffer;
bool isLoaded;
GLuint tex;
float ang,iniRotX,iniRotY,iniRotZ;
Model *mdl;
bool Hide;
AUX_RGBImageRec* m_pTextureImage; // Heightmap Data
public:
ModelObject(Model* mdl)
this->mdl=mdl;
Redraw();
void Redraw()
Hide=false;
ang=-0;
iniRotX=1;
iniRotY=0;
iniRotZ=0;
if(displayList!=-1)
displayList=-1;
groupBuffer=NULL;
void BuildTexture(int i)
if(mdl->groups[i]->capacity.texCoordsSize>0)
try
m_pTextureImage = auxDIBImageLoad( mdl->tex_name ); // Utilize GLaux's Bitmap Load Routine
glGenTextures( 1, &tex ); // Get An Open ID
glBindTexture( GL_TEXTURE_2D, tex ); // Bind The Texture
glTexImage2D( GL_TEXTURE_2D, 0, 3, m_pTextureImage->sizeX, m_pTextureImage->sizeY, 0, GL_RGB, GL_UNSIGNED_BYTE, m_pTextureImage->data );
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
// Free The Texture Data
if( m_pTextureImage )
if( m_pTextureImage->data )
free( m_pTextureImage->data );
free( m_pTextureImage );
catch(std::exception &ex)
void BuildVBO()
int index=0;
groupBuffer=new GroupObject[mdl->groupsSize];
for(int i=0;i<mdl->groupsSize;i++)
BuildTexture(i);
groupBuffer[i].buffer=new GLuint[VBO_BUFFER_SIZE];
// Generate And Bind The Vertex Buffer
glGenBuffersARB( 1, &groupBuffer[i].buffer[0] ); // Get A Valid Name
glBindBufferARB( GL_ARRAY_BUFFER_ARB, groupBuffer[i].buffer[0] ); // Bind The Buffer
glBufferDataARB( GL_ARRAY_BUFFER_ARB,mdl->groups[i]->capacity.vertsSize*sizeof(mdl_vert), mdl->groups[i]->verts, GL_STATIC_DRAW_ARB );
// Generate And Bind The Normal Buffer
glGenBuffersARB( 1, &groupBuffer[i].buffer[1] ); // Get A Valid Name
glBindBufferARB( GL_ARRAY_BUFFER_ARB, groupBuffer[i].buffer[1] ); // Bind The Buffer
glBufferDataARB( GL_ARRAY_BUFFER_ARB,mdl->groups[i]->capacity.normalsSize*sizeof(mdl_normal), mdl->groups[i]->normals, GL_STATIC_DRAW_ARB );
// Generate And Bind The Texture Buffer
glGenBuffersARB( 1, &groupBuffer[i].buffer[2] ); // Get A Valid Name
glBindBufferARB( GL_ARRAY_BUFFER_ARB, groupBuffer[i].buffer[2] ); // Bind The Buffer
glBufferDataARB( GL_ARRAY_BUFFER_ARB,mdl->groups[i]->capacity.texCoordsSize*sizeof(mdl_texCoord), mdl->groups[i]->texCoords, GL_STATIC_DRAW_ARB );
// Generate And Bind The Index Buffer
glGenBuffersARB(1, &groupBuffer[i].buffer[3]);
glBindBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB, groupBuffer[i].buffer[3]);
glBufferDataARB(GL_ELEMENT_ARRAY_BUFFER_ARB, mdl->groups[i]->capacity.indicesSize*sizeof(unsigned int), mdl->groups[i]->indices.vertIndices, GL_STATIC_DRAW_ARB);
void render()
if(!Hide)
if(Drawer.vboSupported())
if(groupBuffer==NULL)
BuildVBO();
glRotatef(ang,iniRotX,iniRotY,iniRotZ);
for(int i=0;i<mdl->groupsSize;i++)
// Enable Pointers
glEnableClientState( GL_VERTEX_ARRAY ); // Disable Vertex Arrays
glEnableClientState( GL_NORMAL_ARRAY ); // Enable Normal Arrays
glEnableClientState( GL_TEXTURE_COORD_ARRAY ); // Enable Texture Coord Arrays
glBindBufferARB( GL_ARRAY_BUFFER_ARB, groupBuffer[i].buffer[0] );
glVertexPointer(3, GL_FLOAT, 0, BUFFER_OFFSET(0));
glBindBufferARB( GL_ARRAY_BUFFER_ARB, groupBuffer[i].buffer[1] );
glNormalPointer(GL_FLOAT,0, BUFFER_OFFSET(0));
glClientActiveTexture(GL_TEXTURE0);
glBindBufferARB( GL_ARRAY_BUFFER_ARB, groupBuffer[i].buffer[2] );
glTexCoordPointer(2,GL_FLOAT,0,BUFFER_OFFSET(0));
glBindBufferARB( GL_ELEMENT_ARRAY_BUFFER, groupBuffer[i].buffer[3]);
glIndexPointer(GL_UNSIGNED_INT,0,BUFFER_OFFSET(0));
glDrawElements( GL_TRIANGLES, mdl->groups[i]->capacity.indicesSize,GL_UNSIGNED_INT, 0); // Draw All Of The Triangles At Once
// Disable Pointers
glDisableClientState( GL_VERTEX_ARRAY ); // Disable Vertex Arrays
glDisableClientState( GL_NORMAL_ARRAY ); // Enable Normal Arrays
glDisableClientState( GL_TEXTURE_COORD_ARRAY ); // Enable Texture Coord Arrays
glRotatef(-ang,iniRotX,iniRotY,iniRotZ);
else
if(this->displayList==-1)
displayList = glGenLists(1);
glNewList(displayList,GL_COMPILE_AND_EXECUTE);
glRotatef(ang,iniRotX,iniRotY,iniRotZ);
for(int j=0;j<mdl->groupsSize;j++)
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, tex);
// Enable Pointers
BuildTexture(j);
//glColor3f(((float)(rand()%256)/256.0f),((float)(rand()%256)/256.0f),((float)(rand()%256)/256.0f));
for(int i=0;i<mdl->groups[j]->capacity.indicesSize;i+=3)
int iv1=mdl->groups[j]->indices.vertIndices[i];
int in1=mdl->groups[j]->indices.normalIndices[i];
int it1=mdl->groups[j]->indices.texIndices[i];
int iv2=mdl->groups[j]->indices.vertIndices[i+1];
int in2=mdl->groups[j]->indices.normalIndices[i+1];
int it2=mdl->groups[j]->indices.texIndices[i+1];
int iv3=mdl->groups[j]->indices.vertIndices[i+2];
int in3=mdl->groups[j]->indices.normalIndices[i+2];
int it3=mdl->groups[j]->indices.texIndices[i+2];
glBegin(GL_TRIANGLES);
glTexCoord2f(mdl->groups[j]->texCoords[it1].u,mdl->groups[j]->texCoords[it1].v);
glNormal3f(mdl->groups[j]->normals[in1].x,mdl->groups[j]->normals[in1].y,mdl->groups[j]->normals[in1].z);
glVertex3f(mdl->groups[j]->verts[iv1].x,mdl->groups[j]->verts[iv1].y,mdl->groups[j]->verts[iv1].z);
glTexCoord2f(mdl->groups[j]->texCoords[it2].u,mdl->groups[j]->texCoords[it2].v);
glNormal3f(mdl->groups[j]->normals[in2].x,mdl->groups[j]->normals[in2].y,mdl->groups[j]->normals[in2].z);
glVertex3f(mdl->groups[j]->verts[iv2].x,mdl->groups[j]->verts[iv2].y,mdl->groups[j]->verts[iv2].z);
glTexCoord2f(mdl->groups[j]->texCoords[it3].u,mdl->groups[j]->texCoords[it3].v);
glNormal3f(mdl->groups[j]->normals[in3].x,mdl->groups[j]->normals[in3].y,mdl->groups[j]->normals[in3].z);
glVertex3f(mdl->groups[j]->verts[iv3].x,mdl->groups[j]->verts[iv3].y,mdl->groups[j]->verts[iv3].z);
glEnd();
glDisable(GL_TEXTURE_2D);
glRotatef(-ang,iniRotX,iniRotY,iniRotZ);
glEndList();
glCallList(displayList);
else
glCallList(displayList);
【问题讨论】：
发布一个完整的、最小的程序来演示这个问题。 【参考方案1】：OpenGL 中没有纹理索引。这种位置和纹理的分离在建模软件中很常见，因为它更易于管理。但是在 OpenGL 中，纹理坐标的数量需要与位置的数量完全相同，因此它们都可以使用相同的索引进行索引。
这将要求您重建所有缓冲区，以便模型中出现的每个顶点索引、法线索引和 texcoord 索引的组合都可以映射到用于 OpenGL 渲染的单个索引。我会尝试写一些伪代码：
struct Trinity
int iv, in, it;
bool operator <(const Trinity &t) const // implement less-than operator as required by std::map
return iv < t.iv || (iv == t.iv && (in < t.in || (in == t.in && it < t.it)));
;
#include <map>
#include <vector>
for(int j=0;j<mdl->groupsSize;j++) // for each object ...
int next_index = 0; // next index to be assigned
std::map<int, Trinity> index_map; // map of collada indices to OpenGL indices
std::vector<int> new_indices; // new indices that can be used for drawing with OpenGL
std::vector<float> new_positions, new_texcoords, new_normals; // other arrays
for(int i=0;i<mdl->groups[j]->capacity.indicesSize;i++) // for each vertex ...
Trinity t;
t.iv = mdl->groups[j]->indices.vertIndices[i];
t.in = mdl->groups[j]->indices.normalIndices[i];
t.it = mdl->groups[j]->indices.texIndices[i];
// go through all the vertices' indices
int index;
if(index_map.find(t) != index_map.end())
index = index_map[t]; // we already saw this combination of indices, reuse it
else
index = next_index; // this is new; assign a new index
++ next_index;
index_map[t] = index; // store the index in the map
new_positions.push_back(mdl->groups[j]->verts[t.iv].x);
new_positions.push_back(mdl->groups[j]->verts[t.iv].y);
new_positions.push_back(mdl->groups[j]->verts[t.iv].z);
new_texcoords.push_back(mdl->groups[j]->texCoords[t.it].u);
new_texcoords.push_back(mdl->groups[j]->texCoords[t.it].v);
new_normals.push_back(mdl->groups[j]->normals[t.in].x);
new_normals.push_back(mdl->groups[j]->normals[t.in].y);
new_normals.push_back(mdl->groups[j]->normals[t.in].z);
// add this particular combination of coordinates at the end of the buffers
// translate the combination of iv, in, it to a single index
new_indices.push_back(index);
// store it in the array
// object data ready to pass to VBOs
现在您可以将 new_indices、new_positions、new_normals 和 new_texcoords 放入 VBO 并渲染它们。我希望这会有所帮助...
【讨论】：
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