2d text artifact when depth test is enable Opengl - c++

Question

Main.cpp
//Variables
const unsigned int width = 896, height = 504;
//Initiating GLFW Window
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
//Creating a GLFW window
window = glfwCreateWindow(width, height, "Jaguar", NULL, NULL);
//Checking if Window was initiated
if (window == NULL) {
std::cout << "GLFW FAILED TO INITIATE WINDOW!\n";
glfwTerminate();
}
glfwMakeContextCurrent(window);
//Centering Window
int windowWidth, windowHeight;
glfwGetWindowSize(window, &windowWidth, &windowHeight);
const GLFWvidmode* mode = glfwGetVideoMode(glfwGetPrimaryMonitor());
glfwSetWindowPos(window, mode->width / 2 - windowWidth / 2, mode->height / 2 - windowHeight / 2);
//Setting-Up window's icon
GLFWimage icon[1];
icon[0].pixels = stbi_load("resources/images/gui/icon/icon.png", &icon[0].width, &icon[0].height, 0, 4);
glfwSetWindowIcon(window, 1, icon);
stbi_image_free(icon[0].pixels);
//Checking if Glad was initiated
if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)) {
std::cout << "GLAD FAILED TO BE INITIATED\n";
}
glEnable(GL_CULL_FACE);
glEnable(GL_BLEND);
glEnable(GL_DEPTH_TEST);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
stbi_set_flip_vertically_on_load(true);
//Setting-Up Viewport
glViewport(0, 0, width, height);
//Intitiating MainMenu
states.push(new MainMenuState(*window, &states));
font.cpp
FT_Library ft;
if (FT_Init_FreeType(&ft)) {
std::cout << "FREETYPE::Failed to initialize library\n";
}
FT_Face face;
if (FT_New_Face(ft, filePath, 0, &face)) {
std::cout << "FREETYPE::Failed to load to font: " << filePath << "\n";
}
// set size to load glyphs as
FT_Set_Pixel_Sizes(face, 0, px);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
for (unsigned char c = 0; c < 128; c++) {
if (FT_Load_Char(face, c, FT_LOAD_RENDER)) {
std::cout << "FREETYPE::Failed to load glpyh\n";
}
unsigned int 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);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_BORDER);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_BORDER);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
Character character = {
texture,
glm::ivec2(face->glyph->bitmap.width, face->glyph->bitmap.rows),
glm::ivec2(face->glyph->bitmap_left, face->glyph->bitmap_top)
,face->glyph->advance.x };
Characters.insert(std::pair<char, Character>(c, character));
}
FT_Done_Face(face);
FT_Done_FreeType(ft);
text.cpp
// activate corresponding render state
shader.use();
glUniform3f(glGetUniformLocation(shader.id, "textColor"), color.x, color.y,
color.z);
glActiveTexture(GL_TEXTURE0);
glBindVertexArray(VAO);
// iterate through all characters
std::string::const_iterator c;
for (c = string.begin(); c != string.end(); c++)
{
Character ch = font.Characters[*c];
float xpos = position.x + ch.bearing.x * scale;
float ypos = position.y - (ch.size.y - ch.bearing.y) * scale;
float w = ch.size.x * scale;
float h = ch.size.y * scale;
// update VBO for each character
float vertices[6][4] = {
{ xpos, ypos + h, 0.0f, 0.0f },
{ xpos, ypos, 0.0f, 1.0f },
{ xpos + w, ypos, 1.0f, 1.0f },
{ xpos, ypos + h, 0.0f, 0.0f },
{ xpos + w, ypos, 1.0f, 1.0f },
{ xpos + w, ypos + h, 1.0f, 0.0f }
};
// render glyph texture over quad
glBindTexture(GL_TEXTURE_2D, ch.textureId);
// update content of VBO memory
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(vertices), vertices);
glBindBuffer(GL_ARRAY_BUFFER, 0);
// render quad
glDrawArrays(GL_TRIANGLES, 0, 6);
// now advance cursors for next glyph (note that advance is number of
1/64 pixels)
position.x += (ch.advance >> 6) * scale; // bitshift by 6 to get value in
pixels (2^6 = 64)
}
glBindVertexArray(0);
glBindTexture(GL_TEXTURE_2D, 0);
Things I have already done:
Render text last
used gl_src_alpha, gl_one_minus_src_alpha
when i have depth testing disable it works just fine do I just enable and disable when needed??
if so how bad/good is it when it come to performance(game smoothness)
I have done some research on it and people are saying enable alpha blending do they mean gl_src_alpha, gl_one_minus_src_alpha

Answer 1

When you use Blending, you must disable the Depth Test. Enable the depth test when you draw the geometry, but disable the depth test before drawing the text. The depth test causes fragments to be discarded depending on the depth function. Blending takes the fragment color outputs from the Fragment Shader and combines them with the colors in the color buffers. Hence Blending is only applied to those fragments that are not discarded.