Question

在OpenGL中，我想使用一些像“\ t”或“\ n”这样的字符文字。但是，在显示文本时，它们完全是igonre。我该怎么办？

    char buffer[100];
    sprintf(buffer, "First float is: %f.\n\tThe second one is: %f", 2.225,3.141592);
    glCallLists(strlen(buffer), GL_UNSIGNED_BYTE, buffer);

// This will display all the text on the same line and ignoring the "\t"

示例（我正在一个大项目中工作。我试图复制下面的opengl绘图例程的基本结构）：

    #include <gl\gl.h>          // Header File For The OpenGL32 Library
    #include <gl\glu.h>         // Header File For The GLu32 Library

    int centreX = 100;
    int centreY = 200;

    GLvoid Print(const char *fmt)   
   {
    char        text[256];

    if (fmt == NULL)                                    
        return;     

    sprintf(buffer,fmt);
    glListBase(256);    
    glCallLists(strlen(text), GL_UNSIGNED_BYTE, text);

}

void DrawScene()    
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glLoadIdentity();

    glColor3f(1.0f,1.0f,0.5f);

    glRasterPos2i((GLint)centreX, (GLint)centreY);
    Print("First float is: %f.\n\tThe second one is: %f", 2.225,3.141592);

}

void main()
{
    while (true)
    {

        DrawScene();

    }
}

Answer 1

首先：OpenGL不知道＆＃34; text＆＃34;是！

您使用的方法依赖于显示列表。对于每个字符代码，创建一个显示列表。这些列表包含绘制单个字母并将变换应用于下一个字母位置的命令。然而，诸如换行符，制表符等控制字符取决于屏幕的位置，即前后的绘图状态。但是在编制显示列表时，我们不知道你将如何处理它们。

你想要的是一个知道如何定位文本的正确的文本布局引擎（如Pango）。此外，您不想使用显示列表（它们已经过时超过15年）并绘制文本字形想要使用类似 freetype-gl 的内容。

Answer 2

datenwolf 100％正确。字符文字如＆＃39; \ t＆＃39;或者＆＃39; \ n＆＃39;尚未由OpenGL / GLUT开发人员实现。

OpenGL / GLUT中的字体往往是位图类型，通常是8x8到16x16像素的维度，并使用x和y坐标绘制到屏幕上，就像任何其他位图一样。

相反，您必须计算x y位置以模拟＆＃39; \ t＆＃39;或者＆＃39; \ n＆＃39;你自己的代码。

有用的链接http://www.codersource.net/2011/01/27/displaying-text-opengl-tutorial-5/

GLUT位图＆amp; stroke font演示代码：

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

void bitmap_output(int x, int y, char *string, void *font){

  int len, i;
  glRasterPos2f(x, y);
  len = (int) strlen(string);
  for (i = 0; i < len; i++) {
    glutBitmapCharacter(font, string[i]);
  }
}

void stroke_output(GLfloat x, GLfloat y, char *format,...){

  va_list args;
  char buffer[200], *p;

  va_start(args, format);
  vsprintf(buffer, format, args);
  va_end(args);
  glPushMatrix();
  glTranslatef(x, y, 0);
  glScalef(0.005, 0.005, 0.005);
  for (p = buffer; *p; p++)
    glutStrokeCharacter(GLUT_STROKE_ROMAN, *p);
  glPopMatrix();
}

void display(void){

  glClear(GL_COLOR_BUFFER_BIT);
  bitmap_output(40, 35, "This is written in a GLUT bitmap font.",
    GLUT_BITMAP_TIMES_ROMAN_24);
  bitmap_output(30, 210, "More bitmap text is a fixed 9 by 15 font.",
    GLUT_BITMAP_9_BY_15);
  bitmap_output(70, 240, "                Helvetica is yet another bitmap font.",
    GLUT_BITMAP_HELVETICA_18);
  glMatrixMode(GL_PROJECTION);
  glPushMatrix();
  glLoadIdentity();
  gluPerspective(40.0, 1.0, 0.1, 20.0);
  glMatrixMode(GL_MODELVIEW);
  glPushMatrix();
  gluLookAt(0.0, 0.0, 4.0,  /* eye is at (0,0,30) */
    0.0, 0.0, 0.0,      /* center is at (0,0,0) */
    0.0, 1.0, 0.);      /* up is in postivie Y direction */
  glPushMatrix();
  glTranslatef(0, 0, -4);
  glRotatef(50, 0, 1, 0);
  stroke_output(-2.5, 1.1, "  This is written in a");
  stroke_output(-2.5, 0, " GLUT stroke font.");
  stroke_output(-2.5, -1.1, "using 3D perspective.");
  glPopMatrix();
  glMatrixMode(GL_MODELVIEW);
  glPopMatrix();
  glMatrixMode(GL_PROJECTION);
  glPopMatrix();
  glMatrixMode(GL_MODELVIEW);
  glFlush();
}

void reshape(int w, int h){

  glViewport(0, 0, w, h);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluOrtho2D(0, w, 0, h);
  glScalef(1, -1, 1);
  glTranslatef(0, -h, 0);
  glMatrixMode(GL_MODELVIEW);
}

int main(int argc, char **argv){

  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
  glutInitWindowSize(465, 250);
  glutCreateWindow("GLUT bitmap & stroke font example");
  glClearColor(1.0, 1.0, 1.0, 1.0);
  glColor3f(0, 0, 0);
  glLineWidth(3.0);
  glutDisplayFunc(display);
  glutReshapeFunc(reshape);
  glutMainLoop();
  return 0;             /* ANSI C requires main to return int. */
}

starwars滚动条演示字体：

// *********************************************************************
// * o p e n g l / G L U T      s t a r   w a r s    s c r o l l e r   *
// *********************************************************************

#include <windows.h>
#include <string.h>
#include <GL\glut.h>
#include <iostream.h>
#define MAX_LINES_OF_STARWARS_QUOTES 32
#define MAX_CHARACTERS_IN_A_LINE 80

GLfloat UpwardsScrollVelocity = -10.0;
float view=20.0;
char starWarsQuotes[MAX_LINES_OF_STARWARS_QUOTES][MAX_CHARACTERS_IN_A_LINE]; // up to 32 lines of quotes 80 characters wide
int numberOfstarWarsQuotes=0,i,ic=0;

//*********************************************
//*  glutIdleFunc(timeTick);                  *
//*********************************************

void timeTick(void){
    if (UpwardsScrollVelocity< -600)  view-=0.000011;
    if(view < 0) {view=20; UpwardsScrollVelocity = -10.0;}
    UpwardsScrollVelocity -= 0.015;
    glutPostRedisplay();
}

//*********************************************
//* RenderToDisplay()                       *
//*********************************************

void RenderToDisplay(){
    int l,lenghOfstarWarsQuotes, i;
    glTranslatef(0.0, -100, UpwardsScrollVelocity);
    glRotatef(-20, 1.0, 0.0, 0.0);
    glScalef(0.1, 0.1, 0.1);

    for(  l=0;l<numberOfstarWarsQuotes;l++){
        lenghOfstarWarsQuotes = (int)strlen(starWarsQuotes[l]);
        glPushMatrix();
        glTranslatef(-(lenghOfstarWarsQuotes*37), -(l*200), 0.0);

        for (i = 0; i < lenghOfstarWarsQuotes; i++) {
            glColor3f((UpwardsScrollVelocity/10)+300+(l*10),(UpwardsScrollVelocity/10)+300+(l*10),0.0);
            glutStrokeCharacter(GLUT_STROKE_ROMAN, starWarsQuotes[l][i]);
        }
        glPopMatrix();
    }
}
//*********************************************
//* glutDisplayFunc(myDisplayFunction);       *
//*********************************************

void myDisplayFunction(void){
  glClear(GL_COLOR_BUFFER_BIT);
  glLoadIdentity();
  gluLookAt(0.0, 30.0, 100.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
  RenderToDisplay();
  glutSwapBuffers();
}

//*********************************************
//* glutReshapeFunc(reshape);               *
//*********************************************

void reshape(int w, int h){
  glViewport(0, 0, w, h);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluPerspective(60, 1.0, 1.0, 3200);
  glMatrixMode(GL_MODELVIEW);
}

//*********************************************
//* int main()                                *
//*********************************************

int main(){
    strcpy(starWarsQuotes[0],"S t a r w a r s    q u o t e s ");
    strcpy(starWarsQuotes[1],"Character literals test : \t \n \r \0 ......");
    strcpy(starWarsQuotes[2],"I’m Luke Skywalker, I’m here to rescue you.");
    strcpy(starWarsQuotes[3],"Luke, I am your father!");
    strcpy(starWarsQuotes[4],"Obi-Wan has taught you well");
    strcpy(starWarsQuotes[5],"The force is strong with this one");
    strcpy(starWarsQuotes[6],"I find your lack of faith disturbing");
    strcpy(starWarsQuotes[7],"Great, kid. Don’t get cocky");
    numberOfstarWarsQuotes=8;

    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
    glutInitWindowSize(800, 400);
    glutCreateWindow("StarWars scroller");
    glClearColor(0.0, 0.0, 0.0, 1.0);
    glLineWidth(3);

    glutDisplayFunc(myDisplayFunction);
    glutReshapeFunc(reshape);
    glutIdleFunc(timeTick);
    glutMainLoop();

    return 0;
}

OpenGL文本忽略转义序列

2 个答案: