使用Freetype2进行OpenGL字体渲染

概述我正在尝试使用OpenGL渲染freetype字体,遵循 http://en.wikibooks.org/wiki/OpenGL_Programming/Modern_OpenGL_Tutorial_Text_Rendering_02发布的示例. 我已经能够从字体生成纹理图集,创建着色器和创建四边形.我似乎被困在的是将纹理传递到着色器和/或为我的四边形获得正确的UV.现在一直在努力奋斗,真的需要帮 我正在尝试使用OpenGL渲染freetype字体,遵循 http://en.wikibooks.org/wiki/OpenGL_Programming/Modern_OpenGL_Tutorial_Text_Rendering_02发布的示例.

我已经能够从字体生成纹理图集,创建着色器和创建四边形.我似乎被困在的是将纹理传递到着色器和/或为我的四边形获得正确的UV.现在一直在努力奋斗,真的需要帮助.

以下是我用来创建纹理图集的结构.

struct FontCharacter    {        float advanceX;        float advanceY;        float bitmapWIDth;        float bitmapHeight;        float bitmapleft;        float bitmaptop;        float uvOffsetX;        float uvOffsetY;    };    struct FontTextureAtlas    {        gluint texture;        gluint textureUniform;        int wIDth;        int height;        FontCharacter characters[128];        FontTextureAtlas(FT_Face face,int h,gluint tUniform)        {            FT_Set_Pixel_Sizes(face,h);            FT_GlyphSlot glyphSlot = face->glyph;            int roww = 0;            int rowh = 0;            wIDth = 0;            height = 0;            memset(characters,sizeof(FontCharacter));            for (int i = 32; i < 128; i++)            {                if (FT_Load_Char(face,i,FT_LOAD_RENDER))                {                    std::cout << "Loading character %c Failed\n",i;                    continue;                }                if (roww + glyphSlot->bitmap.wIDth + 1 >= MAX_WIDTH)                {                    wIDth = std::fmax(wIDth,roww);                    height += rowh;                    roww = 0;                    rowh = 0;                }                roww += glyphSlot->bitmap.wIDth + 1;                rowh = std::fmax(rowh,glyphSlot->bitmap.rows);            }            wIDth = std::fmax(wIDth,roww);            height += rowh;            glGenTextures(1,&texture);            if (glGetError() != GL_NO_ERROR)            {                std::cout << "glGenTextures Failed\n";            }            glActiveTexture(GL_TEXTURE0 + texture);            if (glGetError() != GL_NO_ERROR)            {                std::cout << "glActiveTexture Failed\n";            }            glBindTexture(GL_TEXTURE_2D,texture);            if (glGetError() != GL_NO_ERROR)            {                std::cout << "glBindTexture Failed\n";            }            gluniform1i(tUniform,0);            textureUniform = tUniform;            glTexImage2D(GL_TEXTURE_2D,GL_RED,wIDth,height,GL_UNSIGNED_BYTE,0);            if (glGetError() != GL_NO_ERROR)            {                std::cout << "glTexImage2D Failed\n";            }            glPixelStorei(GL_UNPACK_AlignmENT,1);            if (glGetError() != GL_NO_ERROR)            {                std::cout << "glPixelStorei Failed\n";            }            glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S,GL_CLAMP_TO_EDGE);            if (glGetError() != GL_NO_ERROR)            {                std::cout << "glTexParameteri Failed\n";            }            glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T,GL_TEXTURE_MIN_FILTER,GL_liNEAR);            if (glGetError() != GL_NO_ERROR)            {                std::cout << "glTexParameteri Failed\n";            }            glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_liNEAR);            if (glGetError() != GL_NO_ERROR)            {                std::cout << "glTexParameteri Failed\n";            }            int ox = 0;            int oy = 0;            rowh = 0;            for (int i = 32; i < 128; i++)            {                if (FT_Load_Char(face,i;                    continue;                }                if (ox + glyphSlot->bitmap.wIDth + 1 >= MAX_WIDTH)                 {                    oy += rowh;                    rowh = 0;                    ox = 0;                }                glTexSubImage2D(GL_TEXTURE_2D,ox,oy,glyphSlot->bitmap.wIDth,glyphSlot->bitmap.rows,glyphSlot->bitmap.buffer);                if (glGetError() != GL_NO_ERROR)                {                    std::cout << "BORKED AGAIN\n";                }                characters[i].advanceX = glyphSlot->advance.x >> 6;                characters[i].advanceY = glyphSlot->advance.y >> 6;                characters[i].bitmapWIDth = glyphSlot->bitmap.wIDth;                characters[i].bitmapHeight = glyphSlot->bitmap.rows;                characters[i].bitmapleft = glyphSlot->bitmap_left;                characters[i].bitmaptop = glyphSlot->bitmap_top;                characters[i].uvOffsetX = ox / (float)wIDth;                characters[i].uvOffsetY = oy / (float)height;                rowh = std::fmax(rowh,glyphSlot->bitmap.rows);                ox += glyphSlot->bitmap.wIDth + 1;            }            std::cout << "Generated a " << wIDth << "x " << height << " (" << wIDth * height / 1024 << " kb) texture atlas.\n";        }        ~FontTextureAtlas()        {            glDeleteTextures(1,&texture);        }

渲染器中使用的局部变量和函数头

class RenderCore{    FT_library library;            FT_Face face;            FontTextureAtlas* a48;            FontTextureAtlas* a24;            FontTextureAtlas* a12;            gluint vbo;            gluint vao;            gluint m_posUV;            gluint m_colorIN;            gluint m_texture;            int InitFT();            voID RenderText(const char* text,FontTextureAtlas* atlas,float x,float y,float sx,float sy);}

这是我加载字体的地方.

int RenderCore::InitFT(){    if (FT_Init_FreeType(&library))    {        std::cout << "Could not Initialize freetype library.\n";        return 0;    }    /* Load a Font */    if (FT_New_Face(library,"assets/Fonts/arialbd.ttf",&face))    {        std::cout << "Could not open Font assets/Fonts/DentonBeta2.ttf\n";        return 0;    }    m_shaderManager->CreateProgram("Text");    m_shaderManager->LoadShader("shaders/Text.vertex","TextVS",GL_VERTEX_SHADER);    m_shaderManager->LoadShader("shaders/Text.fragment","TextFS",GL_FRAGMENT_SHADER);    m_shaderManager->AttachShader("TextVS","Text");    m_shaderManager->AttachShader("TextFS","Text");    m_shaderManager->linkProgram("Text");    m_shaderManager->UseProgram("Text");    m_shaderManager->UseProgram("Text");    m_colorIN = m_shaderManager->GetUniformlocation("Text","inputcolor");    m_texture = m_shaderManager->GetUniformlocation("Text","texture");    // Create the vertex buffer object    glGenBuffers(1,&vbo);    glGenVertexArrays(1,&vao);    /* Create texture atlasses for several Font sizes */    a48 = new FontTextureAtlas(face,48,m_texture);    a24 = new FontTextureAtlas(face,24,m_texture);    a12 = new FontTextureAtlas(face,12,m_texture);}

渲染功能.

voID RenderCore::RenderText(const char* text,float sy)    {        m_shaderManager->UseProgram("Text");        const unsigned char* p;        std::vector<glm::vec4> coords;        int c = 0;        for (p = (const unsigned char*)text; *p; p++)        {            float x2 = x + atlas->characters[*p].bitmapleft * sx;            float y2 = -y - atlas->characters[*p].bitmaptop * sy;            float w = atlas->characters[*p].bitmapWIDth * sx;            float h = atlas->characters[*p].bitmapHeight * sy;            x += atlas->characters[*p].advanceX * sx;            y += atlas->characters[*p].advanceY * sy;            if (!w || !h)                continue;            coords.push_back(                glm::vec4(                x2,-y2,atlas->characters[*p].uvOffsetX,atlas->characters[*p].uvOffsetY)                );            coords.push_back(                glm::vec4(                x2 + w,atlas->characters[*p].uvOffsetX + atlas->characters[*p].bitmapWIDth / atlas->wIDth,atlas->characters[*p].uvOffsetY)                );            coords.push_back(                glm::vec4(                x2,-y2 - h,atlas->characters[*p].uvOffsetY + atlas->characters[*p].bitmapHeight / atlas->height)                );            coords.push_back(                glm::vec4(                x2 + w,atlas->characters[*p].uvOffsetY)                );            coords.push_back(                glm::vec4(                x2,atlas->characters[*p].uvOffsetY + atlas->characters[*p].bitmapHeight / atlas->height)                );            coords.push_back(                glm::vec4(                x2 + w,atlas->characters[*p].uvOffsetY + atlas->characters[*p].bitmapHeight / atlas->height)                );        }        glEnable(GL_BLEND);        glBlendFunc(GL_SRC_Alpha,GL_ONE_MINUS_SRC_Alpha);        glActiveTexture(GL_TEXTURE0 + atlas->texture);        gluniform1i(atlas->textureUniform,0);        glBindTexture(GL_TEXTURE_2D,atlas->texture);        m_shaderManager->SetUniform(1,glm::vec4(0,1,1),m_colorIN);        glBindBuffer(GL_ARRAY_BUFFER,vbo);        glBufferData(GL_ARRAY_BUFFER,coords.size() * sizeof(glm::vec4),coords.data(),GL_DYNAMIC_DRAW);        //Generate VAO        glBindVertexArray(vao);        //position        glEnabLevertexAttribarray(0);        glVertexAttribPointer(0,4,GL_float,GL_FALSE,sizeof(glm::vec4),(voID*)0);        glBindVertexArray(vao);        glDrawArrays(GL_TRIANGLE_STRIP,coords.size());        gldisabLevertexAttribarray(0);        m_shaderManager->resetProgram();    }

顶点着色器

#version 440in vec4 pos_uv;out vec2 uv;voID main(){    gl_position = vec4(pos_uv.xy,1);    uv = pos_uv.zw;}

片段着色器

#version 440    in vec2 uv;    uniform sampler2D texture;    uniform vec4 inputcolor;    out vec4 color;    voID main()    {        color = vec4(inputcolor.rgb,texture2D(texture,uv).a);    }

使用gDeBUGger,我可以看到纹理图谱已经正确生成,VBO似乎也很好.结果只是屏幕上的一堆正方形,但我真的不知道为什么.我认为将纹理传递到着色器可能会出现问题,除Alpha通道外的所有通道都是空的,Alpha始终为1.

解决方法 管理解决问题,而不是glActiveTexture(GL_TEXTURE0纹理);它应该只有glActiveTexture(GL_TEXTURE0);

我假设glActiveTexture绑定到程序中的特定索引而不是所有纹理.

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