在C++中使用GLUT/OpenGL绘制文本,您需要使用一个库,例如FreeType。FreeType是一个用于处理字体文件的软件开发工具包,它可以让您轻松地在OpenGL应用程序中渲染文本。以下是一个简单的步骤来实现这个目标:
#include <ft2build.h>
#include FT_FREETYPE_H
FT_Library ft;
if (FT_Init_FreeType(&ft))
std::cout << "ERROR::FREETYPE: Could not init FreeType Library"<< std::endl;
FT_Face face;
if (FT_New_Face(ft, "path/to/font/file", 0, &face))
std::cout << "ERROR::FREETYPE: Failed to load font"<< std::endl;
FT_Set_Pixel_Sizes(face, 0, 48);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
for (GLubyte c = 0; c < 128; c++)
{
if (FT_Load_Char(face, c, FT_LOAD_RENDER))
{
std::cout << "ERROR::FREETYTPE: Failed to load Glyph"<< std::endl;
continue;
}
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
);
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);
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));
}
std::string text = "Hello, World!";
glUseProgram(shaderProgram);
glUniform3f(glGetUniformLocation(shaderProgram, "textColor"), 1.0f, 1.0f, 1.0f);
glActiveTexture(GL_TEXTURE0);
for (char c : text)
{
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;
glBindTexture(GL_TEXTURE_2D, ch.TextureID);
glBindVertexArray(VAO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(GLfloat) * 6 * 4, glm::value_ptr(glm::vec4(xpos, ypos + h, 0.0, 0.0)));
glBufferSubData(GL_ARRAY_BUFFER, sizeof(GLfloat) * 6 * 4, sizeof(GLfloat) * 6 * 4, glm::value_ptr(glm::vec4(xpos, ypos, 0.0, 0.0)));
glBufferSubData(GL_ARRAY_BUFFER, sizeof(GLfloat) * 12 * 4, sizeof(GLfloat) * 6 * 4, glm::value_ptr(glm::vec4(xpos + w, ypos, 0.0, 1.0)));
glBufferSubData(GL_ARRAY_BUFFER, sizeof(GLfloat) * 18 * 4, sizeof(GLfloat) * 6 * 4, glm::value_ptr(glm::vec4(xpos + w, ypos + h, 0.0, 1.0)));
glDrawArrays(GL_TRIANGLES, 0, 6);
x += (ch.Advance >> 6) * scale;
}
glBindVertexArray(0);
glBindTexture(GL_TEXTURE_2D, 0);
通过这些步骤,您可以在C++中使用GLUT/OpenGL绘制文本。
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