使用glutBitmapString調整字體大小

Question

我目前使用Glut的函數glutBitmapString覆蓋我的窗口上的文本。我知道我可以使用不同的位圖字體指定字體/大小。但是，可能的最大文本是GLUT_BITMAP_TIMES_ROMAN_24，是否可以使用更大的字體打印2D文本？或者有什麼方法可以調整glutBitmapString顯示的字體大小嗎？

Answer 1

將您的文本渲染爲紋理，然後使用您想要的任何縮放因子渲染具有該紋理的四邊形。

事情是這樣的：

#include <GL/glew.h> 
#include <GL/freeglut.h> 
#include <cmath> 

GLuint tex = 0, fbo = 0, rbo = 0; 
GLuint fbo_w = 0, fbo_h = 0; 
bool SetFboSize(int width, int height) 
{ 
    int max_size; 
    glGetIntegerv(GL_MAX_RENDERBUFFER_SIZE_EXT, &max_size); 
    if(width > max_size || height > max_size) return false; 

    fbo_w = width; 
    fbo_h = height; 

    // create FBO 
    if(fbo) glDeleteFramebuffersEXT(1, &fbo); 
    glGenFramebuffersEXT(1, &fbo); 
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);  

    // create and attach a new texture as the FBO's color buffer 
    if(tex) glDeleteTextures(1, &tex); 
    glGenTextures(1, &tex); 
    glBindTexture(GL_TEXTURE_2D, tex); 
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); 
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); 
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); 
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); 
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL); 
    glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, tex, 0); 

    // create and attach a new depth buffer to currently bound FBO 
    if(rbo) glDeleteRenderbuffersEXT(1, &rbo); 
    glGenRenderbuffersEXT(1, &rbo); 
    glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, rbo); 
    glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT, width, height); 
    glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT, GL_RENDERBUFFER_EXT, rbo); 

    if(GL_FRAMEBUFFER_COMPLETE_EXT != glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT)) 
    { 
     return false; 
    } 
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0); // unbind fbo 
    return true; 
} 

void display() 
{ 
    // render to texture 
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo); 
    glBindTexture(GL_TEXTURE_2D, 0); 
    { 
     glViewport(0, 0, fbo_w, fbo_h); 
     glClearColor(0, 0, 0, 0); 
     glClear(GL_COLOR_BUFFER_BIT); 

     glMatrixMode(GL_PROJECTION); 
     glLoadIdentity(); 
     glMatrixMode(GL_MODELVIEW); 
     glLoadIdentity(); 

     glColor3ub(255, 0, 0); 
     glWindowPos2i(0, 0); 
     glutBitmapString(GLUT_BITMAP_TIMES_ROMAN_24, (unsigned char*)"Hello, world!"); 
    } 

    // render to screen 
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0); 
    { 
     int w = glutGet(GLUT_WINDOW_WIDTH); 
     int h = glutGet(GLUT_WINDOW_HEIGHT); 
     glViewport(0, 0, w, h); 
     glClearColor(0, 0, 0, 0); 
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 

     glMatrixMode(GL_PROJECTION); 
     glLoadIdentity(); 
     double ar = w/(double)h; 
     glOrtho(-2 * ar, 2 * ar, -2, 2, -1, 1); 

     glMatrixMode(GL_MODELVIEW); 
     glLoadIdentity(); 

     glColor3ub(255, 255, 255); 
     glEnable(GL_TEXTURE_2D); 
     glBindTexture(GL_TEXTURE_2D, tex); 
     float scale = sin((double)glutGet(GLUT_ELAPSED_TIME)/1000.0f); 
     glScalef(scale, scale, 1); 
     glBegin(GL_QUADS); 
     glTexCoord2i(0, 0); 
     glVertex2i(-1, -1); 
     glTexCoord2i(1, 0); 
     glVertex2i( 1, -1); 
     glTexCoord2i(1, 1); 
     glVertex2i( 1, 1); 
     glTexCoord2i(0, 1); 
     glVertex2i(-1, 1); 
     glEnd(); 
    } 

    glutSwapBuffers(); 
} 

void timer(int extra) 
{ 
    glutPostRedisplay(); 
    glutTimerFunc(16, timer, 0); 
} 

int main(int argc, char **argv) 
{ 
    glutInit(&argc, argv); 
    glutInitDisplayMode(GLUT_RGBA | GLUT_DEPTH | GLUT_DOUBLE); 
    glutInitWindowSize(640, 480); 
    glutCreateWindow("GLUT"); 
    glewInit(); 

    if(!GLEW_VERSION_1_4) 
     return -1; 
    if(!GLEW_EXT_framebuffer_object) 
     return -1; 
    if(!SetFboSize(200, 50)) 
     return -1; 

    glutDisplayFunc(display); 
    glutTimerFunc(0, timer, 0); 
    glutMainLoop(); 
    return 0; 
}