如何使用点图元将纹理映射到由参数方程渲染的球体
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【中文标题】如何使用点图元将纹理映射到由参数方程渲染的球体【英文标题】：How to map texture to sphere that rendered by parametric equation using points primitive 【发布时间】：2018-01-22 11:05:03 【问题描述】：是否可以将纹理映射到由参数方程生成并使用 GL_POINTS 基元渲染的球体？如果可能的话，它是如何完成的，在我的代码中，我从网上复制代码图像加载代码并按照指示加载它。我没有遵循它们的一件事是指定纹理坐标的顶点，我不确定在使用 Sphere 和 GL_POINTS 基元渲染它时如何准确指定它。
我正在为我的项目使用旧的 OpenGL2 并进行太阳系模拟
这是repository to the code，它是公开的
这就是我生成球体的方式
// void Sphere::render () method, inside src/sphere.cpp - line 28
void Sphere::render ()
unsigned int angle = 0, angle2 = 0;
const double degree_to_rad = 3.14 / 180.0;
double value = .0, value2 = .0;
if ( this -> texture_file_name != "" )
glEnable ( GL_TEXTURE_2D );
glBindTexture( GL_TEXTURE_2D, this -> texture );
glBegin ( GL_POINTS );
for ( ; angle < 360; ++ angle )
value = angle * degree_to_rad;
for ( ; angle2 < 180; ++ angle2 )
value2 = angle2 * degree_to_rad;
/*/////////////////////////////////////////////
// do I need to do sth in here like glTexCoord2d ( ... ) ?
////////////////////////////////////////////*/
glVertex3d (
this -> calculateX ( value, value2 ),
this -> calculateY ( value, value2 ),
this -> calculateZ ( value )
);
angle2 = 0;
glEnd ();
if ( this -> texture_file_name != "" )
glDisable ( GL_TEXTURE_2D );
;
// void Sphere::draw () method, src/sphere.cpp - line 75
void Sphere::draw ()
glPushMatrix ();
glTranslated (
this -> coordinate [ 0 ],
this -> coordinate [ 1 ],
this -> coordinate [ 2 ]
);
glRotated (
this -> angle_degree,
this -> rotation [ 0 ],
this -> rotation [ 1 ],
this -> rotation [ 2 ]
);
this -> render ();
glPopMatrix ();
;
double Sphere::calculateX ( const double theta_degree_angle, const double phi_degree_angle )
return this -> radius * sin ( theta_degree_angle ) * cos ( phi_degree_angle );
;
double Sphere::calculateY ( const double theta_degree_angle, const double phi_degree_angle )
return this -> radius * sin ( theta_degree_angle ) * sin ( phi_degree_angle );
;
double Sphere::calculateZ ( const double theta_degree_angle )
return this -> radius * cos ( theta_degree_angle );
;
这是我的 loadTexture 方法
void Object::loadTexture ()
int & w = this -> texture_width, & h = this -> texture_height;
unsigned char * data = new unsigned char [ w * h * 3 ];
FILE * file;
try
file = fopen ( this -> texture_file_name.c_str () , "rb" );
if ( !file ) return;
fread ( data, w * h * 3, 1, file );
fclose ( file );
catch ( std::exception & error )
std::cout << "Loading Texture Error: " << error.what () << std::endl;
glGenTextures ( 1, & this -> texture );
glBindTexture ( GL_TEXTURE_2D, this -> texture );
glTexImage2D( GL_TEXTURE_2D, 0, GL_RGB, w, h, 0, GL_RGB, GL_UNSIGNED_BYTE, data );
glTexEnvf( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL );
glTexParameterf ( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
glTexParameterf ( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT );
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT );
delete [] data;
;
void Object::setTexture ( const char * file_name, const int width, const int height )
this -> texture_file_name = file_name;
this -> texture_width = width;
this -> texture_height = height;
this -> loadTexture ();
;
这是我的 main.cpp
// main.cpp
// gloabl vars
NonStd::Sphere sun = NonStd::Sphere ( 10 );
NonStd::Sphere earth = NonStd::Sphere ( 3 );
NonStd::Sphere moon = NonStd::Sphere ( 1 );
NonStd::Object space = NonStd::Object ();
void render ();
void modelInit ();
void idle ();
void windowOnChange ( int width, int height );
void mouseOnDrag ( int x, int y );
int main ( int args_len, char ** args_context )
glutInit ( &args_len, args_context );
glutInitDisplayMode ( GLUT_SINGLE );
glutInitWindowSize ( WINDOW_WIDTH, WINDOW_HEIGHT );
glutInitWindowPosition ( 100, 100 );
glutCreateWindow ( "Solar System Simulation" );
glEnable ( GL_NORMALIZE );
glEnable ( GL_COLOR_MATERIAL );
// all models initialization
modelInit ();
// event handlers
glutDisplayFunc ( render );
glutReshapeFunc ( windowOnChange );
// glutMotionFunc ( mouseOnDrag );
// global idle func
glutIdleFunc ( idle );
glutMainLoop ();
return 0;
;
void render ()
glClearColor ( .2, .3, .5, .8 );
glClear ( GL_COLOR_BUFFER_BIT );
if ( sun.isObjectShown () )
sun.draw ();
if ( earth.isObjectShown () )
earth.draw ();
if ( moon.isObjectShown () )
moon.draw ();
glFlush ();
;
void modelInit ()
// object visibility default is false
sun.setVisible ( true );
// move to proper position to for object for better viewing
sun.translateZ ( -90.0 );
// set object texture
sun.setTexture ( "resources/earth.jpg", 100, 100 );
// spin default is false, toggle it for spinning
sun.toggleSpin ();
earth.setVisible ( true );
earth.translateZ ( -90.0 );
earth.translateX ( 26.0 );
earth.setTexture ( "resources/earth.jpg", 100, 100 );
earth.toggleSpin ();
earth.setSpinSpeed ( 2 );
moon.setVisible ( true );
moon.translateZ ( -90.0 );
moon.translateX ( 20.0 );
moon.setTexture ( "resources/earth.jpg", 100, 100 );
moon.toggleSpin ();
;
After I set the texture on my sphere object, the sphere turn into this yellow color and before setting the texture, it was white, does this mean the texture already set but I have not yet specify the texture coordinate for it ?
仅供参考：该项目说它是 2D，但实际上我是在 3D 中进行的，只是为了澄清它。
【问题讨论】：
您必须在问题本身中显示最少但完整的代码。链接到外部资源只能作为补充材料。另外：目前还不清楚你在做什么。球体本身是由参数方程生成的，还是每个球体都只是一个点？ 好的，我会在里面添加一个 GL_POINTS 是用来渲染点的。你想把纹理应用到什么地方？你想以什么结束？点应该改变颜色，还是球体应该被填充？ @BartekBanachewicz 我希望我的球体结束，说它是一个地球，所以我想将地球纹理映射到它 @BartekBanachewicz 好的，我将尝试将其渲染为 GL_TRIANGLE_FAN 并使用纹理坐标 【参考方案1】：球体既可以通过镶嵌现有对象（如二十面体）来创建，也可以通过堆叠圆盘来创建。
堆叠光盘：
以下代码通过堆叠多个圆盘 (layers) 创建一个球体。每一层的周边都有circumferenceTiles 瓦片。 U 纹理坐标环绕在圆周上。 V纹理坐标从球体的南极包裹到北极。
void CreateSphereMesh( int layers, int circumferenceTiles, std::vector<float> &va, std::vector<int> &ia )
const float pi = 3.1414927f;
// create the vertex attributes
va.reserve( (layers+1)*(circumferenceTiles+1)*5 ); // 5 floats: x, y, z, u, v
for ( int il = 0; il <= layers; ++ il )
float layer_rel = (float)il / (float)layers;
float layer_ang = (1.0f - 2.0f * layer_rel) * pi/2.0f ;
float layer_sin = std::sin( layer_ang );
float layer_cos = std::cos( layer_ang );
for ( int ic = 0; ic <= circumferenceTiles; ic ++ )
float circum_rel = (float)ic / (float)circumferenceTiles;
float cricum_ang = circum_rel * 2.0f*pi - pi;
float circum_sin = std::sin( cricum_ang );
float circum_cos = std::cos( cricum_ang );
va.push_back( layer_cos * circum_cos ); // x
va.push_back( layer_cos * circum_sin ); // y
va.push_back( layer_sin ); // z
va.push_back( circum_rel ); // u
va.push_back( 1.0f - layer_rel ); // v
// create the face indices
ia.reserve( layers*circumferenceTiles*6 );
for ( int il = 0; il < layers; ++ il )
for ( int ic = 0; ic < circumferenceTiles; ic ++ )
int i0 = il * (circumferenceTiles+1) + ic;
int i1 = i0 + 1;
int i3 = i0 + circumferenceTiles+1;
int i2 = i3 + 1;
int faces[] i0, i1, i2, i0, i2, i3 ;
ia.insert(ia.end(), faces+(il==0?3:0), faces+(il==layers-1?3:6));
固定函数 pipline 的顶点数组对象可以这样指定：
GLuint vao;
glGenVertexArrays( 1, &vao );
glBindVertexArray( vao );
GLuint vbo;
glGenBuffers( 1, &vbo );
glBindBuffer( GL_ARRAY_BUFFER, vbo );
glBufferData( GL_ARRAY_BUFFER, va.size()*sizeof(*va.data()), va.data(), GL_STATIC_DRAW );
GLuint ibo;
glGenBuffers( 1, &ibo );
glBindBuffer( GL_ELEMENT_ARRAY_BUFFER, ibo );
glBufferData( GL_ELEMENT_ARRAY_BUFFER, ia.size()*sizeof(*ia.data()), ia.data(), GL_STATIC_DRAW );
glVertexPointer( 3, GL_FLOAT, 5*sizeof(*va.data()), 0 );
glEnableClientState( GL_VERTEX_ARRAY );
glTexCoordPointer( 2, GL_FLOAT, 5*sizeof(*va.data()), (void*)(3*sizeof(*va.data())) );
glEnableClientState( GL_TEXTURE_COORD_ARRAY );
glBindVertexArray( 0 );
glBindBuffer( GL_ARRAY_BUFFER, 0 );
glBindBuffer( GL_ELEMENT_ARRAY_BUFFER, 0 );
对于现代 OpenGL，通用顶点属性数据数组必须这样定义：
GLint avert_loc = ....;
GLint atexc_loc = ....;
glVertexAttribPointer( avert_loc, 3, GL_FLOAT, GL_FALSE, 5*sizeof(*va.data()), 0 );
glEnableVertexAttribArray( avert_loc );
glVertexAttribPointer( atexc_loc, 2, GL_FLOAT, GL_FALSE, 5*sizeof(*va.data()), (void*)(3*sizeof(*va.data())) );
glEnableVertexAttribArray( atexc_loc );
最后的绘图操作：
glEnable( GL_TEXTURE_2D ); // for fixed function pipeline only
glBindVertexArray( vao );
glDrawElements( GL_TRIANGLES, (GLsizei)ia.size(), GL_UNSIGNED_INT, 0 );
glBindVertexArray( 0 );
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