在 OpenGL 中使用 Freetype 的字体渲染问题不起作用
Issue with Font Rendering using Freetype in OpenGL is not working
我遇到字体渲染问题。为此，我正在使用教程 https://learnopengl.com/In-Practice/Text-Rendering。
我正在 OpenGLESV3 中开发应用程序。
我为 3D 对象绘制、加载纹理和最后的字体渲染制作了不同的着色器程序。
我在 3D 对象和纹理绘制完成后绘制字体。
但是问题是当我使用正交投影绘制时看不到字体。我只能看到 3D 对象和纹理。 （尽管着色器不同）
当我仅使用正交投影绘制字体时，它绘制得非常完美。
我确定是投影设置的问题，但我无法找出问题所在。
有人可以帮忙吗？
这是我的渲染循环中的代码
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glViewport(0, 0, (GLsizei)SCR_WIDTH, (GLsizei)SCR_HEIGHT);
/********************************* 3D objects Rendering ********************************************************/
glUseProgram(shaderpgmPoints);
projection = glm::perspective(glm::radians(camspec.fov), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f);
glUniformMatrix4fv(glGetUniformLocation(shaderpgmPoints, "projection"), 1, false, &projection[0][0]);
view = glm::lookAt(camspec.cameraPos, camspec.cameraPos + camspec.cameraFront, camspec.cameraUp);
glUniformMatrix4fv(glGetUniformLocation(shaderpgmPoints, "view"), 1, false, &view[0][0]);
model = glm::mat4(1.0f);
glUniformMatrix4fv(glGetUniformLocation(shaderpgmPoints, "model"), 1, false, &model[0][0]);
glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);
glBindBuffer(GL_ARRAY_BUFFER, quadBufferObject);
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0);
glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, 0, (void*)64);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glBindBuffer(GL_ARRAY_BUFFER, leftlaneBufferObject);
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0);
glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, 0, (void*)192);
;
glEnable(GL_PROGRAM_POINT_SIZE);
glDrawArrays(GL_LINES, 0, 12);
glDisable(GL_BLEND);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glBindBuffer(GL_ARRAY_BUFFER, rightlaneBufferObject);
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0);
glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, 0, (void*)32);
glLineWidth(10.0f);
glDrawArrays(GL_LINES, 0, 2);
glDisable(GL_BLEND);
glDisableVertexAttribArray(0);
glDisableVertexAttribArray(1);
glUseProgram(0);
/********************************* 3D objects Rendering -End ********************************************************/
/********************************* Texture Rendering ********************************************************/
glUseProgram(shaderpgmTexture);
glm::mat4 transform = glm::mat4(1.0f);
transform = glm::translate(transform, glm::vec3(0.0f, 0.0f, 0.0f));
glUniformMatrix4fv(glGetUniformLocation(shaderpgmTexture, "transform"), 1, false, &transform[0][0]);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glUniform1i(glGetUniformLocation(shaderpgmTexture, "outputTexture"), 1);
glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, camTexture);
glBindBuffer(GL_ARRAY_BUFFER, camTextureBufferObject);
// position attribute
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
// texture coord attribute
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(3 * sizeof(float)));
glEnableVertexAttribArray(1);
glDrawArrays(GL_QUADS, 0, 4);
glDisable(GL_BLEND);
glDisableVertexAttribArray(0);
glDisableVertexAttribArray(1);
glUseProgram(0);
/********************************* Texture Rendering - End ********************************************************/
/********************************* Font Rendering ********************************************************/
glDisable(GL_DEPTH_TEST);
glUseProgram(shaderpgmFont);
glEnable(GL_CULL_FACE);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glm::mat4 project = glm::ortho(0.0f, static_cast<GLfloat>(SCR_WIDTH), 0.0f, static_cast<GLfloat>(SCR_HEIGHT));
glUniformMatrix4fv(glGetUniformLocation(shaderpgmFont, "projection"), 1, false, &project[0][0]);
glUniform3f(glGetUniformLocation(shaderpgmFont, "textColor"), 1.0f, 0.0f, 0.0f);
glActiveTexture(GL_TEXTURE0);
GLfloat scale = 1.0f;
GLfloat x = 10.0f;
GLfloat y = 10.0f;
std::string text = "THE";
std::string::const_iterator c;
for (c = text.begin(); c != text.end(); c++)
{
Character ch = Characters[*c];
GLfloat xpos = x + ch.Bearing.x * scale;
GLfloat ypos = y - (ch.Size.y - ch.Bearing.y) * scale;
GLfloat w = ch.Size.x * scale;
GLfloat h = ch.Size.y * scale;
GLfloat vertices[6][4] = {
{ xpos, ypos + h, 0.0, 0.0 },
{ xpos, ypos, 0.0, 1.0 },
{ xpos + w, ypos, 1.0, 1.0 },
{ xpos, ypos + h, 0.0, 0.0 },
{ xpos + w, ypos, 1.0, 1.0 },
{ xpos + w, ypos + h, 1.0, 0.0 }
};
// Render glyph texture over quad
glBindTexture(GL_TEXTURE_2D, ch.TextureID);
// Update content of VBO memory
glBindBuffer(GL_ARRAY_BUFFER, FontVertexBufferObject);
glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(vertices), vertices); // Be sure to use glBufferSubData and not glBufferData
glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);
glDrawArrays(GL_TRIANGLES, 0, 6);
glBindBuffer(GL_ARRAY_BUFFER, 0);
// Now advance cursors for next glyph (note that advance is number of 1/64 pixels)
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))
}
glBindTexture(GL_TEXTURE_2D, 0);
glDisable(GL_BLEND);
glDisable(GL_CULL_FACE);
glUseProgram(0);
glEnable(GL_DEPTH_TEST);
/********************************* Font Rendering - End********************************************************/
我正在像这样初始化字体缓冲区
glDisable(GL_DEPTH_TEST);
glEnable(GL_CULL_FACE);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glUseProgram(shaderpgmFont);
// 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;
// Load font as face
FT_Face face;
if (FT_New_Face(ft, "fonts/arial.ttf", 0, &face))
{
std::cout << "ERROR::FREETYPE: Failed to load font" << std::endl;
}
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 (GLubyte 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_ALPHA,
face->glyph->bitmap.width,
face->glyph->bitmap.rows,
0,
GL_ALPHA,
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),
face->glyph->advance.x
};
Characters.insert(std::pair<GLchar, 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
glGenBuffers(1, &FontVertexBufferObject);
glBindBuffer(GL_ARRAY_BUFFER, FontVertexBufferObject);
glBufferData(GL_ARRAY_BUFFER, sizeof(GLfloat) * 6 * 4, NULL, GL_DYNAMIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(GLfloat), 0);
glEnableVertexAttribArray(1);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(GLfloat), (void*)(2 * sizeof(GLfloat)));
glBindBuffer(GL_ARRAY_BUFFER, 0);
}
glUseProgram(0);
glDisable(GL_CULL_FACE);
glDisable(GL_BLEND);
glEnable(GL_DEPTH_TEST);
在您的初始化函数中，您通过 glVertexAttribPointer 设置了一些 OpenGL 状态，稍后会被破坏。
要解决此问题，请修改您的文本呈现代码，使其在 glBindBuffer 之后进行两次调用 glVertexAttribPointer。
我遇到字体渲染问题。为此，我正在使用教程 https://learnopengl.com/In-Practice/Text-Rendering。 我正在 OpenGLESV3 中开发应用程序。
我为 3D 对象绘制、加载纹理和最后的字体渲染制作了不同的着色器程序。 我在 3D 对象和纹理绘制完成后绘制字体。 但是问题是当我使用正交投影绘制时看不到字体。我只能看到 3D 对象和纹理。 （尽管着色器不同）
当我仅使用正交投影绘制字体时，它绘制得非常完美。
我确定是投影设置的问题，但我无法找出问题所在。 有人可以帮忙吗？
这是我的渲染循环中的代码
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glViewport(0, 0, (GLsizei)SCR_WIDTH, (GLsizei)SCR_HEIGHT);
/********************************* 3D objects Rendering ********************************************************/
glUseProgram(shaderpgmPoints);
projection = glm::perspective(glm::radians(camspec.fov), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f);
glUniformMatrix4fv(glGetUniformLocation(shaderpgmPoints, "projection"), 1, false, &projection[0][0]);
view = glm::lookAt(camspec.cameraPos, camspec.cameraPos + camspec.cameraFront, camspec.cameraUp);
glUniformMatrix4fv(glGetUniformLocation(shaderpgmPoints, "view"), 1, false, &view[0][0]);
model = glm::mat4(1.0f);
glUniformMatrix4fv(glGetUniformLocation(shaderpgmPoints, "model"), 1, false, &model[0][0]);
glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);
glBindBuffer(GL_ARRAY_BUFFER, quadBufferObject);
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0);
glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, 0, (void*)64);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glBindBuffer(GL_ARRAY_BUFFER, leftlaneBufferObject);
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0);
glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, 0, (void*)192);
;
glEnable(GL_PROGRAM_POINT_SIZE);
glDrawArrays(GL_LINES, 0, 12);
glDisable(GL_BLEND);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glBindBuffer(GL_ARRAY_BUFFER, rightlaneBufferObject);
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0);
glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, 0, (void*)32);
glLineWidth(10.0f);
glDrawArrays(GL_LINES, 0, 2);
glDisable(GL_BLEND);
glDisableVertexAttribArray(0);
glDisableVertexAttribArray(1);
glUseProgram(0);
/********************************* 3D objects Rendering -End ********************************************************/
/********************************* Texture Rendering ********************************************************/
glUseProgram(shaderpgmTexture);
glm::mat4 transform = glm::mat4(1.0f);
transform = glm::translate(transform, glm::vec3(0.0f, 0.0f, 0.0f));
glUniformMatrix4fv(glGetUniformLocation(shaderpgmTexture, "transform"), 1, false, &transform[0][0]);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glUniform1i(glGetUniformLocation(shaderpgmTexture, "outputTexture"), 1);
glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, camTexture);
glBindBuffer(GL_ARRAY_BUFFER, camTextureBufferObject);
// position attribute
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
// texture coord attribute
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(3 * sizeof(float)));
glEnableVertexAttribArray(1);
glDrawArrays(GL_QUADS, 0, 4);
glDisable(GL_BLEND);
glDisableVertexAttribArray(0);
glDisableVertexAttribArray(1);
glUseProgram(0);
/********************************* Texture Rendering - End ********************************************************/
/********************************* Font Rendering ********************************************************/
glDisable(GL_DEPTH_TEST);
glUseProgram(shaderpgmFont);
glEnable(GL_CULL_FACE);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glm::mat4 project = glm::ortho(0.0f, static_cast<GLfloat>(SCR_WIDTH), 0.0f, static_cast<GLfloat>(SCR_HEIGHT));
glUniformMatrix4fv(glGetUniformLocation(shaderpgmFont, "projection"), 1, false, &project[0][0]);
glUniform3f(glGetUniformLocation(shaderpgmFont, "textColor"), 1.0f, 0.0f, 0.0f);
glActiveTexture(GL_TEXTURE0);
GLfloat scale = 1.0f;
GLfloat x = 10.0f;
GLfloat y = 10.0f;
std::string text = "THE";
std::string::const_iterator c;
for (c = text.begin(); c != text.end(); c++)
{
Character ch = Characters[*c];
GLfloat xpos = x + ch.Bearing.x * scale;
GLfloat ypos = y - (ch.Size.y - ch.Bearing.y) * scale;
GLfloat w = ch.Size.x * scale;
GLfloat h = ch.Size.y * scale;
GLfloat vertices[6][4] = {
{ xpos, ypos + h, 0.0, 0.0 },
{ xpos, ypos, 0.0, 1.0 },
{ xpos + w, ypos, 1.0, 1.0 },
{ xpos, ypos + h, 0.0, 0.0 },
{ xpos + w, ypos, 1.0, 1.0 },
{ xpos + w, ypos + h, 1.0, 0.0 }
};
// Render glyph texture over quad
glBindTexture(GL_TEXTURE_2D, ch.TextureID);
// Update content of VBO memory
glBindBuffer(GL_ARRAY_BUFFER, FontVertexBufferObject);
glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(vertices), vertices); // Be sure to use glBufferSubData and not glBufferData
glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);
glDrawArrays(GL_TRIANGLES, 0, 6);
glBindBuffer(GL_ARRAY_BUFFER, 0);
// Now advance cursors for next glyph (note that advance is number of 1/64 pixels)
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))
}
glBindTexture(GL_TEXTURE_2D, 0);
glDisable(GL_BLEND);
glDisable(GL_CULL_FACE);
glUseProgram(0);
glEnable(GL_DEPTH_TEST);
/********************************* Font Rendering - End********************************************************/
我正在像这样初始化字体缓冲区
glDisable(GL_DEPTH_TEST);
glEnable(GL_CULL_FACE);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glUseProgram(shaderpgmFont);
// 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;
// Load font as face
FT_Face face;
if (FT_New_Face(ft, "fonts/arial.ttf", 0, &face))
{
std::cout << "ERROR::FREETYPE: Failed to load font" << std::endl;
}
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 (GLubyte 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_ALPHA,
face->glyph->bitmap.width,
face->glyph->bitmap.rows,
0,
GL_ALPHA,
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),
face->glyph->advance.x
};
Characters.insert(std::pair<GLchar, 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
glGenBuffers(1, &FontVertexBufferObject);
glBindBuffer(GL_ARRAY_BUFFER, FontVertexBufferObject);
glBufferData(GL_ARRAY_BUFFER, sizeof(GLfloat) * 6 * 4, NULL, GL_DYNAMIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(GLfloat), 0);
glEnableVertexAttribArray(1);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(GLfloat), (void*)(2 * sizeof(GLfloat)));
glBindBuffer(GL_ARRAY_BUFFER, 0);
}
glUseProgram(0);
glDisable(GL_CULL_FACE);
glDisable(GL_BLEND);
glEnable(GL_DEPTH_TEST);
在您的初始化函数中，您通过 glVertexAttribPointer 设置了一些 OpenGL 状态，稍后会被破坏。
要解决此问题，请修改您的文本呈现代码，使其在 glBindBuffer 之后进行两次调用 glVertexAttribPointer。