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c - 如何在 OpenGL 1.1 中创建带纹理的四边形?

转载 作者:太空宇宙 更新时间:2023-11-04 03:25:27 26 4
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我正在玩 OpenGL,试图编写一个概念证明来绘制一个带有 2x2 GL_RGB GL_FLOAT 位图的 2x2 四边形纹理。

根据我的理解;为此,我必须

  1. 通过调用 glEnable(GL_TEXTURE_2D) 启用 2d 纹理。
  2. 通过调用 glTexture2D 用像素数据填充纹理。
  3. 设置 glOrtho 以匹配窗口坐标系(0、宽度、0、高度、-1、1)。

  4. 调用 glGenTextures 获取唯一标识我的纹理的标识符。

  5. 通过调用 glBindTexture 选择我的纹理。
  6. 通过调用 glTexParameteri 设置纹理参数。
  7. 使用具有指定纹理坐标和顶点的 glBegin(glEnd)/glDrawArrays

我对 glBegin 的尝试看起来像

#include <gl/glut.h>
#include <stdio.h>

const char *appTitle = "OpenGL Texture Experiment";

static GLfloat identity4f[] = {
1, 0, 0, 0,
0, 1, 0, 0,
0, 0, 1, 0,
0, 0, 0, 1
};

static GLfloat pixels[] = {
1, 0, 0,
0, 1, 0,
0, 0, 1,
1, 1, 1
};

GLuint texid[] = {-1};

static inline void display()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glClearColor(0, 0, 0, 0);

glColor3f(0, 1, 0);

glBindTexture(GL_TEXTURE_2D, texid[0]);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glBegin(GL_TRIANGLES);

glTexCoord2f(0, 0);
glVertex2f(0, 0);

glTexCoord2f(0, 1);
glVertex2f(0, 2);

glTexCoord2f(1, 0);
glVertex2f(2, 2);

glTexCoord2f(1, 0);
glVertex2f(2, 2);

glTexCoord2f(1, 1);
glVertex2f(2, 0);

glTexCoord2f(0, 0);
glVertex2f(0, 0);

glEnd();

glutSwapBuffers();
}

static inline void init()
{
glEnable(GL_TEXTURE_2D);

glGenTextures(1, texid);

/* anonymous scope: set texture */
{
GLenum target = GL_TEXTURE_2D;
GLint level = 0;
GLint internalformat = GL_RGB;
GLsizei width = 2;
GLsizei height = 2;
GLint border = 0;
GLenum format = GL_RGB;
GLenum type = GL_FLOAT;
const GLvoid *data = pixels;

glTexImage2D (
target,
level,
internalformat,
width,
height,
border,
format,
type,
data
);
}
printf("got texture #%d.\n", texid[0]);

typedef struct {
double x_left;
double x_right;
double y_bottom;
double y_top;
double z_near;
double z_far;
} glOrtho_arguments;


const struct {
GLint width;
GLint height;
} glutInfo = {
glutGet(GLUT_WINDOW_WIDTH),
glutGet(GLUT_WINDOW_HEIGHT)
};

glOrtho_arguments args;
args.x_left = 0;
args.x_right = glutInfo.width;
args.y_bottom = glutInfo.height;
args.y_top = 0;
args.z_near = -1;
args.z_far = 1;

glClearColor(0, 0, 0, 0);
glMatrixMode(GL_PROJECTION);
glMultMatrixf(identity4f);
glOrtho (
args.x_left,
args.x_right,
args.y_bottom,
args.y_top,
args.z_near,
args.z_far
);
}

int main(int argc, char **argv)
{
glMatrixMode(GL_MODELVIEW);
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
glutInitWindowSize(300, 300);
glutInitWindowPosition(100, 100);
glutCreateWindow(appTitle);
init();
glutDisplayFunc(display);
glutMainLoop();

return 0;
}

我对 glDrawArrays 的尝试是这样的:

#include <gl/glut.h>
#include <stdio.h>

const char *appTitle = "OpenGL Texture Experiment";

static GLfloat identity4f[] = {
1, 0, 0, 0,
0, 1, 0, 0,
0, 0, 1, 0,
0, 0, 0, 1
};

static GLfloat pixels[] = {
1, 0, 0,
0, 1, 0,
0, 0, 1,
1, 1, 1
};

static GLfloat vertices[] = {
0, 0, 0,
0, 2, 0,
2, 2, 0,
2, 2, 0,
2, 0, 0,
0, 0, 0
};

static GLfloat colors[] = {
0, 1, 0,
0, 1, 0,
0, 1, 0,
0, 1, 0,
0, 1, 0,
0, 1, 0
};

static GLfloat coords[] = {
0, 0, 0,
0, 1, 0,
1, 0, 0,
1, 1, 0
};

GLuint texid[] = {-1};

static inline void display()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glClearColor(0, 0, 0, 0);

glColor3f(0, 1, 0);

glBindTexture(GL_TEXTURE_2D, texid[0]);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

glTexCoordPointer(3, GL_FLOAT, 0, coords);
glVertexPointer(3, GL_FLOAT, 0, vertices);
glColorPointer(3, GL_FLOAT, 0, colors);
glDrawArrays(GL_TRIANGLES, 0, 6);

glutSwapBuffers();
}

static inline void init()
{
glEnable(GL_TEXTURE_2D);
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_COLOR_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glGenTextures(1, texid);

/* set texture */
{
GLenum target = GL_TEXTURE_2D;
GLint level = 0;
GLint internalformat = GL_RGB;
GLsizei width = 2;
GLsizei height = 2;
GLint border = 0;
GLenum format = GL_RGB;
GLenum type = GL_FLOAT;
const GLvoid *data = pixels;

glTexImage2D (
target,
level,
internalformat,
width,
height,
border,
format,
type,
data
);
}
printf("got texture #%d.\n", texid[0]);

typedef struct {
double x_left;
double x_right;
double y_bottom;
double y_top;
double z_near;
double z_far;
} glOrtho_arguments;

const struct {
GLint width;
GLint height;
} glutInfo = {
glutGet(GLUT_WINDOW_WIDTH),
glutGet(GLUT_WINDOW_HEIGHT)
};

glOrtho_arguments args;
args.x_left = 0;
args.x_right = glutInfo.width;
args.y_bottom = glutInfo.height;
args.y_top = 0;
args.z_near = -1;
args.z_far = 1;

glClearColor(0, 0, 0, 0);
glMatrixMode(GL_PROJECTION);
glMultMatrixf(identity4f);
glOrtho (
args.x_left,
args.x_right,
args.y_bottom,
args.y_top,
args.z_near,
args.z_far
);
}

int main(int argc, char **argv)
{
glMatrixMode(GL_MODELVIEW);
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
glutInitWindowSize(300, 300);
glutInitWindowPosition(100, 100);
glutCreateWindow(appTitle);
init();
glutDisplayFunc(display);
glutMainLoop();

return 0;
}

这里尝试修改工作答案以使用顶点数组,看起来很有趣。

#include <GL/glut.h>
#include <stdio.h>

static GLfloat pixels[] =
{
1, 0, 0,
0, 1, 0,
0, 0, 1,
1, 1, 1
};

GLuint texid[] = { -1 };

static inline void init()
{
glEnable( GL_TEXTURE_2D );
glGenTextures( 1, texid );
glBindTexture( GL_TEXTURE_2D, texid[ 0 ] );
glTexImage2D( GL_TEXTURE_2D, 0, GL_RGB, 2, 2, 0, GL_RGB, GL_FLOAT, pixels );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
}

static inline void display()
{
glClearColor( 0, 0, 0, 0 );
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

glMatrixMode( GL_PROJECTION );
glLoadIdentity();
glOrtho(0, 5, 5, 0, -1, 1 );

glColor3f( 1, 1, 1 );

glBindTexture( GL_TEXTURE_2D, texid[ 0 ] );

glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_COLOR_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);

GLfloat c[] = {
0, 0, 0,
1, 0, 0,
1, 1, 0,
0, 1, 0
};

glVertexPointer(3, GL_FLOAT, 0, c);
glColorPointer(3, GL_FLOAT, 0, pixels);
glTexCoordPointer(3, GL_FLOAT, 0, c);
glDrawArrays(GL_QUADS, 0, 4);

glDisableClientState(GL_VERTEX_ARRAY);
glDisableClientState(GL_COLOR_ARRAY);
glDisableClientState(GL_TEXTURE_COORD_ARRAY);

glutSwapBuffers();
}

int main( int argc, char **argv )
{
glMatrixMode( GL_MODELVIEW );
glutInit( &argc, argv );
glutInitDisplayMode( GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH );
glutInitWindowSize( 300, 300 );
glutCreateWindow( "OpenGL Texture Experiment" );
init();
glutDisplayFunc( display );
glutMainLoop();
return 0;
}

The result only shows a green untextured 2x2 square; I want it to be a 2x2 square with

顶部 2 个像素为红色、绿色,底部两个像素为蓝色和白色。

我做错了什么?

编辑:

这是纹理三角形的概念证明;我认为它会以某种奇怪的方式扭曲,但它的行为却像这样:

enter image description here

#include <gl/glut.h>

const char *appTitle = "OpenGL Basic Template";

static GLuint texid[] = {-1};

static GLfloat pixels[] = {
1, 0, 0,
0, 1, 0,
0, 0, 1,
1, 1, 1
};

static inline void display()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glClearColor((float)0x55/0xff, (float)0x55/0xff, 1, 1);

/**
glBindTexture(GL_TEXTURE_2D, texid[0]);
glBegin(GL_QUADS);
glColor3f(1, 1, 1);
glTexCoord2f(0, 0);
glVertex2f(0, 0);
glTexCoord2f(0, 1);
glVertex2f(0, 1);
glTexCoord2f(1, 1);
glVertex2f(1, 1);
glTexCoord2f(1, 0);
glVertex2f(1, 0);
glEnd();

*/

glBindTexture(GL_TEXTURE_2D, texid[0]);
glBegin(GL_TRIANGLES);
glColor3f(1, 1, 1);
glTexCoord2f(0, 0);
glVertex2f(0, 0);
glTexCoord2f(0, 1);
glVertex2f(0, 1);
glTexCoord2f(1, 1);
glVertex2f(1, 1);
glEnd();

glPushMatrix();
glTranslatef(-1, -1, 0);
glBegin(GL_TRIANGLES);
glColor3f(1, 1, 1);
glTexCoord2f(0, 0);
glVertex2f(0, 0);
glTexCoord2f(1, 1);
glVertex2f(1, 1);
glTexCoord2f(1, 0);
glVertex2f(1, 0);
glEnd();
glPopMatrix();



glColor3f(0, 0, 0);
glLineWidth(1.0);
glBegin(GL_LINES);
glVertex2f(0, 0);
glVertex2f(0, 1);
glVertex2f(0, 1);
glVertex2f(1, 1);
glVertex2f(1, 1);
glVertex2f(0, 0);
glEnd();

glPushMatrix();
glTranslatef(-1, -1, 0);
glBegin(GL_LINES);
glVertex2f(0, 0);
glVertex2f(1, 1);
glVertex2f(1, 1);
glVertex2f(1, 0);
glVertex2f(1, 0);
glVertex2f(0, 0);
glEnd();
glPopMatrix();

glutSwapBuffers();
}

static inline void init()
{
glEnable(GL_TEXTURE_2D);
glGenTextures(1, texid);
glBindTexture(GL_TEXTURE_2D, texid[0]);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 2, 2, 0, GL_RGB, GL_FLOAT, pixels);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

// | there is no overhead for using this
// | but it makes it much more explicit what the values
// | mean!
typedef struct {
double x_left;
double x_right;
double y_bottom;
double y_top;
double z_near;
double z_far;
} glOrtho_arguments;

glOrtho_arguments args;
args.x_left = -1;
args.x_right = 1;
args.y_bottom = -1;
args.y_top = 1;
args.z_near = -1;
args.z_far = 1;

glClearColor(0, 0, 0, 0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho (
args.x_left,
args.x_right,
args.y_bottom,
args.y_top,
args.z_near,
args.z_far
);
}

int main(int argc, char **argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
glutInitWindowSize(300, 300);
glutInitWindowPosition(100, 100);
glutCreateWindow(appTitle);
init();
glutDisplayFunc(display);
glutMainLoop();

return 0;
}

编辑2:

好的,我让它工作了;这是使用四边形的版本:

#include <gl/glut.h>
#include <stdio.h>

const char *appTitle = "OpenGL Texture Experiment";

static GLfloat identity4f[] = {
1, 0, 0, 0,
0, 1, 0, 0,
0, 0, 1, 0,
0, 0, 0, 1
};

static GLfloat pixels[] = {
1, 0, 0,
0, 1, 0,
0, 0, 1,
1, 1, 1
};

static GLfloat vertices[] = {
0, 0,
0, 2,
2, 2,
2, 0,
};

static GLfloat coords[] = {
0, 0,
1, 0,
1, 1,
0, 1
};

GLuint texid[] = {-1};

static inline void display()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glClearColor((float)81/255, (float)81/255, 1, 1);

glColor3f(1, 1, 1);

glBindTexture(GL_TEXTURE_2D, texid[0]);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

glTexCoordPointer(2, GL_FLOAT, 0, coords);
glVertexPointer(2, GL_FLOAT, 0, vertices);
glDrawArrays(GL_QUADS, 0, 4);

glutSwapBuffers();
}

static inline void init()
{
glEnable(GL_TEXTURE_2D);
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glGenTextures(1, texid);

glBindTexture(GL_TEXTURE_2D, texid[0]);
/* set texture */
{
GLenum target = GL_TEXTURE_2D;
GLint level = 0;
GLint internalformat = GL_RGB;
GLsizei width = 2;
GLsizei height = 2;
GLint border = 0;
GLenum format = GL_RGB;
GLenum type = GL_FLOAT;
const GLvoid *data = pixels;

glTexImage2D (
target,
level,
internalformat,
width,
height,
border,
format,
type,
data
);
}
printf("got texture #%d.\n", texid[0]);

typedef struct {
double x_left;
double x_right;
double y_bottom;
double y_top;
double z_near;
double z_far;
} glOrtho_arguments;

const struct {
GLint width;
GLint height;
} glutInfo = {
glutGet(GLUT_WINDOW_WIDTH),
glutGet(GLUT_WINDOW_HEIGHT)
};

glOrtho_arguments args;
args.x_left = 0;
args.x_right = glutInfo.width;
args.y_bottom = glutInfo.height;
args.y_top = 0;
args.z_near = -1;
args.z_far = 1;

glClearColor(0, 0, 0, 0);
glMatrixMode(GL_PROJECTION);
glMultMatrixf(identity4f);
glOrtho (
args.x_left,
args.x_right,
args.y_bottom,
args.y_top,
args.z_near,
args.z_far
);
}

int main(int argc, char **argv)
{
glMatrixMode(GL_MODELVIEW);
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
glutInitWindowSize(300, 300);
glutInitWindowPosition(100, 100);
glutCreateWindow(appTitle);
init();
glutDisplayFunc(display);
glutMainLoop();

return 0;
}

这是一个使用三角形的版本

#include <gl/glut.h>
#include <stdio.h>

const char *appTitle = "OpenGL Texture Experiment";

static GLfloat identity4f[] = {
1, 0, 0, 0,
0, 1, 0, 0,
0, 0, 1, 0,
0, 0, 0, 1
};

static GLfloat pixels[] = {
1, 0, 0,
0, 1, 0,
0, 0, 1,
1, 1, 1
};

static GLfloat vertices[] = {
0, 0,
0, 2,
2, 2,
2, 2,
2, 0,
0, 0
};

static GLfloat coords[] = {
0, 0,
1, 0,
1, 1,
1, 1,
0, 1,
0, 0
};

GLuint texid[] = {-1};

static inline void display()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glClearColor((float)81/255, (float)81/255, 1, 1);

glColor3f(1, 1, 1);

glBindTexture(GL_TEXTURE_2D, texid[0]);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

glTexCoordPointer(2, GL_FLOAT, 0, coords);
glVertexPointer(2, GL_FLOAT, 0, vertices);
glDrawArrays(GL_TRIANGLES, 0, 6);

glutSwapBuffers();
}

static inline void init()
{
glEnable(GL_TEXTURE_2D);
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glGenTextures(1, texid);

glBindTexture(GL_TEXTURE_2D, texid[0]);
/* set texture */
{
GLenum target = GL_TEXTURE_2D;
GLint level = 0;
GLint internalformat = GL_RGB;
GLsizei width = 2;
GLsizei height = 2;
GLint border = 0;
GLenum format = GL_RGB;
GLenum type = GL_FLOAT;
const GLvoid *data = pixels;

glTexImage2D (
target,
level,
internalformat,
width,
height,
border,
format,
type,
data
);
}
printf("got texture #%d.\n", texid[0]);

typedef struct {
double x_left;
double x_right;
double y_bottom;
double y_top;
double z_near;
double z_far;
} glOrtho_arguments;

const struct {
GLint width;
GLint height;
} glutInfo = {
glutGet(GLUT_WINDOW_WIDTH),
glutGet(GLUT_WINDOW_HEIGHT)
};

glOrtho_arguments args;
args.x_left = 0;
args.x_right = glutInfo.width;
args.y_bottom = glutInfo.height;
args.y_top = 0;
args.z_near = -1;
args.z_far = 1;

glClearColor(0, 0, 0, 0);
glMatrixMode(GL_PROJECTION);
glMultMatrixf(identity4f);
glOrtho (
args.x_left,
args.x_right,
args.y_bottom,
args.y_top,
args.z_near,
args.z_far
);
}

int main(int argc, char **argv)
{
glMatrixMode(GL_MODELVIEW);
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
glutInitWindowSize(300, 300);
glutInitWindowPosition(100, 100);
glutCreateWindow(appTitle);
init();
glutDisplayFunc(display);
glutMainLoop();

return 0;
}

enter image description here

最佳答案

开关GL_TEXTURE_ENV GL_DECAL 或在渲染前使用 glColor3f(1, 1, 1) 如果您要坚持使用默认的 GL_MODULATE texenv。

在调用 glTexImage2D() 之前,您还需要 glBindTexture(),以便 OpenGL 知道要填充哪个纹理对象。

一起:

#include <GL/glut.h>
#include <stdio.h>

static GLfloat pixels[] =
{
1, 0, 0,
0, 1, 0,
0, 0, 1,
1, 1, 1
};

GLuint texid[] = { -1 };

static inline void init()
{
glEnable( GL_TEXTURE_2D );
glGenTextures( 1, texid );
glBindTexture( GL_TEXTURE_2D, texid[ 0 ] );
glTexImage2D( GL_TEXTURE_2D, 0, GL_RGB, 2, 2, 0, GL_RGB, GL_FLOAT, pixels );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST );
}

static inline void display()
{
glClearColor( 0, 0, 0, 0 );
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

glMatrixMode( GL_PROJECTION );
glLoadIdentity();
glOrtho( -2, 2, -2, 2, -1, 1 );

glMatrixMode( GL_MODELVIEW );
glLoadIdentity();

glColor3f( 1, 1, 1 );

glBindTexture( GL_TEXTURE_2D, texid[ 0 ] );
glBegin( GL_QUADS );
glTexCoord2f( 0, 0 );
glVertex2f( 0, 0 );
glTexCoord2f( 1, 0 );
glVertex2f( 1, 0 );
glTexCoord2f( 1, 1 );
glVertex2f( 1, 1 );
glTexCoord2f( 0, 1 );
glVertex2f( 0, 1 );
glEnd();

glutSwapBuffers();
}

int main( int argc, char **argv )
{
glMatrixMode( GL_MODELVIEW );
glutInit( &argc, argv );
glutInitDisplayMode( GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH );
glutInitWindowSize( 300, 300 );
glutCreateWindow( "OpenGL Texture Experiment" );
init();
glutDisplayFunc( display );
glutMainLoop();
return 0;
}

关于c - 如何在 OpenGL 1.1 中创建带纹理的四边形?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/41555409/

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