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 440
in 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.
