NeHe教程Qt实现——lesson17

NeHe 系列教程之十四：2D纹理字体

英文教程地址：lesson17

本课展示2D纹理生成字体。

首先是字体库的建立及相关字符输出函数：

namespace {    GLuint  texture[2];                             // Storage For Our Font Texture    GLuint  loop;                                   // Generic Loop Variable    GLfloat cnt1;                                   // 1st Counter Used To Move Text & For Coloring    GLfloat cnt2;                                   // 2nd Counter Used To Move Text & For Coloring    struct FyjBitmapChar    {        QVector<QVector2D> texCoords;        int right; //字符宽度        int height;//字符高度        int ascillValue;    };    struct FyjBitmapFont    {        char *name;        int quality;        FyjBitmapChar *characters;    };    static FyjBitmapChar chars1[128];    static FyjBitmapChar chars2[128];    const FyjBitmapFont font1 = {"standard", 128, chars1};    const FyjBitmapFont font2 = {"Itatic", 128, chars2};    void buildFont()    {        float   cx;                      // Holds Our X Character Coord        float   cy;                     // Holds Our Y Character Coord        glBindTexture(GL_TEXTURE_2D, texture[0]);        for (loop = 0; loop < 256; loop++) {            cx = float(loop%16)/16.0f; //当前字符的x纹理坐标            cy = float(loop/16)/16.0f; //当前字符的y纹理坐标            if (loop < 128) {                chars1[loop].texCoords<<QVector2D(cx, cy + 0.0625f)                     <<QVector2D(cx+0.0625f, cy+0.0625f)                     <<QVector2D(cx+0.0625f, cy)                     <<QVector2D(cx, cy);                chars1[loop].height = 16;                chars1[loop].right = 10;                chars1[loop].ascillValue = loop+32;            } else {                chars2[loop-128].texCoords<<QVector2D(cx, cy + 0.0625f)                                         <<QVector2D(cx+0.0625f, cy+0.0625f)                                         <<QVector2D(cx+0.0625f, cy)                                         <<QVector2D(cx, cy);                chars2[loop-128].height = 12;                chars2[loop-128].right = 10;                chars2[loop-128].ascillValue = loop-128+32;           }        }    }    void renderBitmapCharacter(FyjBitmapChar c, int fontSize)    {        Q_ASSERT_X(c.ascillValue >= 32 && c.ascillValue <= 127,                   "renderBitmapCharacter", "unspported char");        glEnableClientState(GL_VERTEX_ARRAY);        glEnableClientState(GL_TEXTURE_COORD_ARRAY);        QVector<QVector2D> vertices;        vertices<<QVector2D(0, 0)                <<QVector2D(fontSize, 0)                <<QVector2D(fontSize, fontSize)                <<QVector2D(0, fontSize);        glVertexPointer(2, GL_FLOAT, 0, vertices.constData());        glTexCoordPointer(2, GL_FLOAT, 0, c.texCoords.constData());        glDrawArrays(GL_QUADS, 0, 4);        glDisableClientState(GL_VERTEX_ARRAY);        glDisableClientState(GL_TEXTURE_COORD_ARRAY);    }    void renderBitmapString(GLint x, GLint y, QString string, int set, int fontSize)    {        int numOfReturnChar = 0;        if (string.isNull() || string.isEmpty())            return;        if (set > 1)            set = 1;        FyjBitmapFont currentFont;        if (set == 0)            currentFont = font1;        else            currentFont = font2;        glBindTexture(GL_TEXTURE_2D, texture[0]);        glDisable(GL_DEPTH_TEST);        glMatrixMode(GL_PROJECTION);        glPushMatrix();        glLoadIdentity();        glOrtho(0,640,0,480,-1,1);        glMatrixMode(GL_MODELVIEW);        glPushMatrix();        glLoadIdentity();        glTranslated(x, y, 0);        for(int i = 0; i < string.length(); i++) {            char c = string.at(i).toAscii();            if (c == '\n') {                numOfReturnChar++;                glLoadIdentity();                glTranslated(x, y - numOfReturnChar * currentFont.characters[0].height, 0);                continue;            }            renderBitmapCharacter(currentFont.characters[c-32], fontSize);            glTranslated(currentFont.characters[c-32].right * fontSize/16, 0, 0);        }        glMatrixMode(GL_PROJECTION);        glPopMatrix();        glMatrixMode(GL_MODELVIEW);        glPopMatrix();        glEnable(GL_DEPTH_TEST);    }    void glPrint(GLint x, GLint y, int set, int fontSize, const char *fmt, ...)    {        char   text[256];              // Holds Our String        va_list     ap;                 // Pointer To List Of Arguments        if (fmt == NULL)                    // If There's No Text            return;                     // Do Nothing        va_start(ap, fmt);                  // Parses The String For Variables            vsprintf(text, fmt, ap);                // And Converts Symbols To Actual Numbers        va_end(ap);                     // Results Are Stored In Text        renderBitmapString(x, y, QString(text), set, fontSize);    }    void drawTextureMappedQuad()    {        QVector<QVector2D> vertices;        QVector<QVector2D> texCoords;        glEnableClientState(GL_VERTEX_ARRAY);        glEnableClientState(GL_TEXTURE_COORD_ARRAY);        vertices<<QVector2D(-1.0f, 1.0f)               <<QVector2D(1.0f, 1.0f)               <<QVector2D(1.0f,-1.0f)              <<QVector2D(-1.0f,-1.0f);        texCoords<<QVector2D(0.0f,0.0f)                <<QVector2D(1.0f,0.0f)                <<QVector2D(1.0f,1.0f)               <<QVector2D(0.0f,1.0f);        glTexCoordPointer(2, GL_FLOAT, 0, texCoords.constData());        glVertexPointer(2, GL_FLOAT, 0, vertices.constData());        glDrawArrays(GL_QUADS, 0, 4);        glDisableClientState(GL_VERTEX_ARRAY);        glDisableClientState(GL_TEXTURE_COORD_ARRAY);    }}

接着是字体纹理加载：

void MyGLWidget::loadTextures(){    texture[0] = bindTexture(QString(":/Font.bmp"),                             GL_TEXTURE_2D,                             GL_RGBA,                             QGLContext::LinearFilteringBindOption);    // Create Nearest Filtered Texture    glBindTexture(GL_TEXTURE_2D, texture[0]);    texture[1] = bindTexture(QString(":/Bumps.bmp"),                             GL_TEXTURE_2D,                             GL_RGBA,                             QGLContext::LinearFilteringBindOption);    // Create Linear Filtered Texture    glBindTexture(GL_TEXTURE_2D, texture[1]);}

初始化：

void MyGLWidget::initializeGL(){    loadTextures();    glEnable(GL_TEXTURE_2D);    buildFont();    glBlendFunc(GL_SRC_ALPHA,GL_ONE);    glShadeModel(GL_SMOOTH);   // Enables Smooth Shading    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);  // Black Background    glClearDepth(1.0f);             // Depth Buffer Setup    glEnable(GL_DEPTH_TEST);        // Enables Depth Testing    glDepthFunc(GL_LEQUAL);        // The Type Of Depth Test To Do    glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST); // Really Nice Perspective Calculations}

绘制：

void MyGLWidget::paintGL(){    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);  // Clear The Screen And The Depth Buffer    glLoadIdentity();       // Reset The Current Modelview Matrix    glBindTexture(GL_TEXTURE_2D, texture[1]);    glTranslatef(0.0f,0.0f,-5.0f);    glRotatef(45.0f,0.0f,0.0f,1.0f);    glRotatef(cnt1*30.0f,1.0f,1.0f,0.0f);    glDisable(GL_BLEND);    glColor3f(1.0f,1.0f,1.0f);    drawTextureMappedQuad();    glRotatef(90.0f,1.0f,1.0f,0.0f);    drawTextureMappedQuad();    glEnable(GL_BLEND);    glLoadIdentity();    glColor3f(1.0f*float(cos(cnt1)),1.0f*float(sin(cnt2)),1.0f-0.5f*float(cos(cnt1+cnt2)));    glPrint(int((280+250*cos(cnt1))),int(235+200*sin(cnt2)),0, 16, "NeHe");    glColor3f(1.0f*float(sin(cnt2)),1.0f-0.5f*float(cos(cnt1+cnt2)),1.0f*float(cos(cnt1)));    glPrint(int((280+230*cos(cnt2))),int(235+200*sin(cnt1)), 1, 24, "OpenGL");    glColor3f(0.0f,0.0f,1.0f);    glPrint(int(240+200*cos((cnt2+cnt1)/5)),2, 0, 16, "Giuseppe D'Agata");    glColor3f(1.0f,1.0f,1.0f);    glPrint(int(242+200*cos((cnt2+cnt1)/5)),2, 0, 16, "Giuseppe D'Agata");    cnt1+=0.01f;    cnt2+=0.0081f;}

运行效果图：