When using freetype on opengl some letters appear to be on a higher position than they are supposed to be. Letters that should be lower, such as p or g, are instead higher.
It looks like this:
I think this is because the code is not lowering the latters and just use the default position it uses for all letters, but since I'm a bit inexperienced with free type I couldn't figure out how to fix this. Here is my code:
void Text::render_text(std::string text, float x, float y, float z, float scale, glm::vec3 color, float angle_rad)
{
// activate corresponding render state
shader.use();
glUniform3f(glGetUniformLocation(shader.ID, "textColor"), color.x, color.y, color.z);
glActiveTexture(GL_TEXTURE0);
glBindVertexArray(VAO);
GLfloat vertices[6][4] = {
{ 0.0, 1.0, 0.0, 0.0 },
{ 0.0, 0.0, 0.0, 1.0 },
{ 1.0, 0.0, 1.0, 1.0 },
{ 0.0, 1.0, 0.0, 0.0 },
{ 1.0, 0.0, 1.0, 1.0 },
{ 1.0, 1.0, 1.0, 0.0 }
};
// Update content of VBO memory
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(vertices), vertices); // Be sure to use glBufferSubData and not glBufferData
glBindBuffer(GL_ARRAY_BUFFER, 0);
glm::mat4 rotateM = glm::rotate(glm::mat4(1.0f), glm::radians(angle_rad), glm::vec3(0.0f, 0.0f, 1.0f));
glm::mat4 transOriginM = glm::translate(glm::mat4(1.0f), glm::vec3(x, y, z));
// Iterate through all characters
std::string::const_iterator c;
GLfloat char_x = 0.0f;
for (c = text.begin(); c != text.end(); c++)
{
Character ch = Characters[*c];
GLfloat w = ch.Size.x * scale;
GLfloat h = ch.Size.y * scale;
GLfloat xrel = char_x + ch.Bearing.x * scale;
GLfloat yrel = (ch.Size.y - ch.Bearing.y) * scale;
// Now advance cursors for next glyph (note that advance is number of 1/64 pixels)
char_x += (ch.Advance >> 6) * scale; // Bitshift by 6 to get value in pixels (2^6 = 64 (divide amount of 1/64th pixels by 64 to get amount of pixels))
glm::mat4 scaleM = glm::scale(glm::mat4(1.0f), glm::vec3(w, h, 1.0f));
glm::mat4 transRelM = glm::translate(glm::mat4(1.0f), glm::vec3(xrel, yrel, z));
glm::mat4 modelM = transOriginM * rotateM * transRelM * scaleM;
GLint model_loc = glGetUniformLocation(shader.ID, "model");
glUniformMatrix4fv(model_loc, 1, GL_FALSE, glm::value_ptr(modelM));
// Render glyph texture over quad
glBindTexture(GL_TEXTURE_2D, ch.TextureID);
// Render quad
glDrawArrays(GL_TRIANGLES, 0, 6);
}
glBindVertexArray(0);
glBindTexture(GL_TEXTURE_2D, 0);
}
void Text::init()
{
// glfw: initialize and configure
// ------------------------------
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
// glfw window creation
// --------------------
// glad: load all OpenGL function pointers
// ---------------------------------------
// OpenGL stateh-
// ------------
//glEnable(GL_CULL_FACE);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
// compile and setup the shader
// ----------------------------
shader = Shader("./src/opengl/shaders/text.vs", "./src/opengl/shaders/text.fs");
glm::mat4 projection = glm::ortho(0.0f, static_cast<float>(SCR_WIDTH), 0.0f, static_cast<float>(SCR_HEIGHT));
shader.use();
glUniformMatrix4fv(glGetUniformLocation(shader.ID, "projection"), 1, GL_FALSE, glm::value_ptr(projection));
// FreeType
// --------
FT_Library ft;
// All functions return a value different than 0 whenever an error occurred
if (FT_Init_FreeType(&ft))
{
std::cout << "ERROR::FREETYPE: Could not init FreeType Library" << std::endl;
exit(0);
}
std::string font_name = "./src/opengl/fonts/FreeSans.ttf";
// find path to font
// load font as face
FT_Face face;
if (FT_New_Face(ft, font_name.c_str(), 0, &face)) {
std::cout << "ERROR::FREETYPE: Failed to load font" << std::endl;
exit(0) ;
}
else {
// set size to load glyphs as
FT_Set_Pixel_Sizes(face, 0, 48);
// disable byte-alignment restriction
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
// load first 128 characters of ASCII set
for (unsigned char c = 0; c < 128; c++)
{
// Load character glyph
if (FT_Load_Char(face, c, FT_LOAD_RENDER))
{
std::cout << "ERROR::FREETYTPE: Failed to load Glyph" << std::endl;
continue;
}
// generate texture
GLuint texture;
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
glTexImage2D(
GL_TEXTURE_2D,
0,
GL_RED,
face->glyph->bitmap.width,
face->glyph->bitmap.rows,
0,
GL_RED,
GL_UNSIGNED_BYTE,
face->glyph->bitmap.buffer
);
// set texture options
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
// now store character for later use
Character character = {
texture,
glm::ivec2(face->glyph->bitmap.width, face->glyph->bitmap.rows),
glm::ivec2(face->glyph->bitmap_left, face->glyph->bitmap_top),
static_cast<unsigned int>(face->glyph->advance.x)
};
Characters.insert(std::pair<char, Character>(c, character));
}
glBindTexture(GL_TEXTURE_2D, 0);
}
// destroy FreeType once we're finished
FT_Done_Face(face);
FT_Done_FreeType(ft);
// configure VAO/VBO for texture quads
// -----------------------------------
glGenVertexArrays(1, &VAO);
glGenBuffers(1, &VBO);
glBindVertexArray(VAO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
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);
}
Edit: Using different fonts does not effect this bug, it still remains. It seems like bearing of letters g and p are not negative as they are supposed to be.