Freetype2-无法显示/显示字形

问题描述

我正在使用2D游戏引擎，并且想实现文本渲染。我想使用freetype。我有以下代码：

gluint va;
glGenVertexArrays(1,&va);
gluint vb;
glGenBuffers(1,&vb);
glBindVertexArray(va);
glBindBuffer(GL_ARRAY_BUFFER,vb);
glBufferData(GL_ARRAY_BUFFER,sizeof(float) * 6 * 4,NULL,GL_DYNAMIC_DRAW);
glEnabLevertexAttribArray(0);
glVertexAttribPointer(0,4,GL_FLOAT,GL_FALSE,4 * sizeof(float),0);
glBindBuffer(GL_ARRAY_BUFFER,0);
glBindVertexArray(0);

FT_Face testface;
FT_Error error;

error = FT_New_Face(ftlib,"arial.ttf",&testface);

if (error == FT_Err_UnkNown_File_Format)
{
    std::cout << "Font format not supported" << std::endl;
}
else if (error)
{
    std::cout << "Something else" << "\n";
}

error = FT_Set_Pixel_Sizes(testface,48);

if (error)
{
    std::cout << "Problem with set px szes occ\n";
}

glPixelStorei(GL_UNPACK_ALIGNMENT,1);

for (unsigned char c = 0; c < 128; c++)
{
    if (FT_Load_Char(testface,c,FT_LOAD_RENDER))
    {
        std::cout << "Error. Failed to load glyph "<<c<<"\n";
        continue;
    }

    gluint texture;
    glGenTextures(1,&texture);
    glBindTexture(GL_TEXTURE_2D,texture);
    glTexImage2D(
        GL_TEXTURE_2D,GL_RED,testface->glyph->bitmap.width,testface->glyph->bitmap.rows,GL_UNSIGNED_BYTE,testface->glyph->bitmap.buffer
    );

    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S,GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);

    Character newchar = {
        texture,glm::ivec2(testface->glyph->bitmap.width,testface->glyph->bitmap.rows),glm::ivec2(testface->glyph->bitmap_left,testface->glyph->bitmap_top),testface->glyph->advance.x
    };
    characters.insert(std::pair<char,Character>{c,newchar});
}
FT_Done_Face(testface);
//glPixelStorei(GL_UNPACK_ALIGNMENT,4);

gluseProgram(text_shader_program);
gluniform4f(glGetUniformlocation(text_shader_program,"textColor"),1.f,1.f);
glActiveTexture(GL_TEXTURE0);

std::string::const_iterator c;
std::string text = "TEST";
glBindVertexArray(va);
float x = 0.f;
for (c = text.begin(); c != text.end(); c++)
{
    Character ch = characters[*c];

    float xpos = x + ch.bearing.x;
    float ypos = 0.f - (ch.size.y - ch.bearing.y);

    float w = ch.size.x;
    float h = ch.size.y;

    float vertices[6][4] = {
        {xpos,ypos + h,0.f,0.f},{xpos,ypos,1.f},{xpos + w,0.f}
    };

    glBindTexture(GL_TEXTURE_2D,ch.textureID);

    glBindBuffer(GL_ARRAY_BUFFER,vb);
    glBufferSubData(GL_ARRAY_BUFFER,sizeof(vertices),vertices);
    glBindBuffer(GL_ARRAY_BUFFER,0);

    glDrawArrays(GL_TRIANGLES,6);

    x += (ch.advance >> 6);
}
glBindVertexArray(0);
glBindTexture(GL_TEXTURE_2D,0);

我使用以下代码初始化库（在上述代码发生之前）

FT_Error error = FT_Init_FreeType(&ftlib);
if (error)
{
    std::cout << "????" << std::endl;
}

人脸和库正确初始化，字形已加载，但未绘制任何内容。我不使用摄像头，因此所有坐标都在-1到1的空间内。

我具有以下用于着色的着色器： 顶点着色器

#version 330 core
layout(location=0) in vec4 vertex;

out vec2 TextCoords;

void main() {
    gl_Position = vec4(vertex.xy,0.0,1.0);
    TextCoords = vertex.zw;
}

fragmentshader

#version 330 core
in vec3 TextCoords;

out vec4 color;

uniform sampler2D text;
uniform vec4 textColor;

void main(){
    vec4 sampled = vec4(1.0,1.0,texture(text,TextCoords).r);
    color = textColor * sampled;
}

更新： 我将FT_Set_Pixel_Sizes(testface,48)行更改为FT_Set_Pixel_Sizes(testface,1)，并在文本应有的地方得到了一个巨大的灰色矩形。

有人有什么想法吗？

解决方法

问题似乎是未使用z坐标的结果。问题是，当使用坐标空间-1到1时，文本呈现的比例过大，无法看到或识别。解决方案是将z坐标用作静态相机视图，因此对于500x500窗口，边框为-250.f和250.f