1
我正在玩OpenGL,試圖寫一個2x2 GL_RGB GL_FLOAT位圖繪製2x2四紋理的概念驗證。如何在OpenGL 1.1中創建紋理四元組?
從我的理解;要做到這一點,我必須
- 通過致電
glEnable(GL_TEXTURE_2D)
啓用2D紋理。 - 通過調用
glTexture2D
填充像素數據的紋理。 設置
glOrtho
以匹配窗口座標系(0,寬度,0,高度,-1,1)。請致電
glGenTextures
獲取標識符以唯一標識我的紋理。- 通過調用
glBindTexture
來選擇我的紋理。 - 通過調用
glTexParameteri
來設置紋理參數。 - 使用
glBegin
(glEnd
)/glDrawArrays
與指定的紋理座標和垂直。
我與在glBegin嘗試看起來像
#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;
}
我與調用glDrawArrays嘗試看起來像:
#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
};
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;
}
這裏的修改工作答案使用頂點數組的嘗試,它看起來很滑稽。
#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
頂部2像素是紅色,綠色和底部兩個是藍色和白色。
我在做什麼錯?
編輯:
這裏的概念紋理三角形的證明;我認爲它會在一些奇怪的方式彎曲,而是它的行爲它的工作原理是這樣的:
#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;
}
EDIT2:
確定我得到它的工作;這裏使用的版本四邊形:
#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;
}
,這裏是一個使用三角形
#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;
}
我設置glColor3f 1,1,1,但它仍然顯示其作爲4個綠色像素。我不知道如何使用glTexEnv;我應該使用,而不是glTexImage2D? – Dmitry
@Dmitry:你也有一個具有約束力的問題,答案更新。 – genpfault
如果我將glOrtho更改爲'glOrtho(0,300,300,0,-1,1);'它顯示爲單個白色像素。如何在窗口座標0,0處將其顯示爲{{red,green},{blue,white}}?它似乎工作,如果我'glOrtho(0,200,200,0,-1,1); glTranslatef(5,5,0);'但是如果我刪除了翻譯,它只會再次顯示紅色像素。這也可以用三角形而不是四邊形完成嗎? – Dmitry