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尝试渲染使用FreeType2和this online tutorial的字符，但有一些问题，结果非常不规则。我查看了本网站here和here上的其他问题，并进行了更正，但我仍然非常难过。我将它进行到底，但该位图显示不正确：OpenGL FreeType2位图不渲染
不仅如此，但显示取决于我想要呈现的字符。有些显示为空白，而其他显示为矩形。代码如下，任何意见将不胜感激。
主程序：
#include <iostream>
#include <fstream>
#include <vector>
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#define GLM_FORCE_RADIANS
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtx/transform.hpp>
#include <ft2build.h>
#include FT_FREETYPE_H
#include "OGLT.hpp"
OGLT Toolkit;
GLuint vao, vbo[2], shader, uniform_color, tex, uniform_tex;
static void key_callback(GLFWwindow * window, int key, int scancode, int action, int mods){
if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
glfwSetWindowShouldClose(window, GL_TRUE);
}
void MyInitialize(){
// Initialize FreeType
FT_Library library;
FT_Face face;
int error = FT_Init_FreeType(&library);
if (error){
std::cout << "An error occurred during library initialization!\n";
}
//error = FT_New_Face(library, "open-sans/OpenSans-Regular.ttf", 0, &face);
error = FT_New_Face(library, "/usr/share/fonts/truetype/droid/DroidSans.ttf", 0, &face);
if(error == FT_Err_Unknown_File_Format){
std::cout << "The font file could be opened and read, but it appears " <<
"that its font format is unsupported.\n";
}
else if(error){
std::cout << "Another error code means that the font file could not be " <<
"opened or read, or that it is broken.\n";
}
else std::cout << "Font file sucessfully loaded!\n";
FT_Set_Pixel_Sizes(face, 0, 100);
// Initialize GLEW and load shaders
Toolkit.StartGLEW();
// OpenGL state initialization
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
glPixelStorei(GL_UNPACK_ALIGNMENT,1);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LESS);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
// Vertex buffer initialization
FT_Load_Char(face, 'W', FT_LOAD_RENDER);
FT_GlyphSlot g = face->glyph;
float x = 0.0f, y = 0.0f;
float sx = 2.0/1000.0;
float sy = 2.0/800.0;
float x2 = x + g->bitmap_left * sx;
float y2 = -y - g->bitmap_top * sy;
float w = g->bitmap.width * sx;
float h = g->bitmap.rows * sy;
static float letter[] = {
x2, -y2, 0.0f,
x2+w, -y2, 0.0f,
x2, -y2-h, 0.0f,
x2+w, -y2-h, 0.0f,
};
static float letter_uv[] = {
0.0f, 0.0f,
1.0f, 0.0f,
0.0f, 1.0f,
1.0f, 1.0f
};
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
glGenBuffers(2, vbo);
glBindBuffer(GL_ARRAY_BUFFER, vbo[0]);
glBufferData(GL_ARRAY_BUFFER, sizeof(letter), letter, GL_STATIC_DRAW);
GLuint VertexAttributeID = 0;
glVertexAttribPointer(VertexAttributeID, 3, GL_FLOAT, GL_FALSE, 0, 0);
glEnableVertexAttribArray(VertexAttributeID);
glBindBuffer(GL_ARRAY_BUFFER, vbo[1]);
glBufferData(GL_ARRAY_BUFFER, sizeof(letter_uv), letter, GL_STATIC_DRAW);
GLuint UvAttributeID = 1;
glVertexAttribPointer(UvAttributeID, 2, GL_FLOAT, GL_FALSE, 0, 0);
glEnableVertexAttribArray(UvAttributeID);
glBindVertexArray(0);
glBindBuffer(GL_ARRAY_BUFFER, vbo[0]);
glActiveTexture(GL_TEXTURE0);
glGenTextures(1, &tex);
glBindTexture(GL_TEXTURE_2D, tex);
glTexImage2D(GL_TEXTURE_2D, 0, GL_R8, g->bitmap.width, g->bitmap.rows, 0,
GL_RED, GL_UNSIGNED_BYTE, g->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);
shader = Toolkit.LoadShaders("test_vertex.glsl", "test_fragment.glsl");
uniform_color = glGetUniformLocation(shader, "color");
uniform_tex = glGetUniformLocation(shader, "texture_sampler");
}
void MyDisplay(GLFWwindow * window){
int width, height;
glfwGetFramebufferSize(window, &width, &height);
glViewport(0, 0, width, height);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glUseProgram(shader);
glm::vec4 ColorVec = glm::vec4(0.0f, 1.0f, 0.0f, 1.0f);
glUniform4fv(uniform_color, 1, &ColorVec[0]);
glUniform1i(uniform_tex, 0);
glBindVertexArray(vao);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, tex);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
glBindVertexArray(0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindTexture(GL_TEXTURE_2D, 0);
glUseProgram(0);
}
int main(){
// Initialize window
GLFWwindow * window;
// Initialize the library
if(!glfwInit()) return -1;
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
// Create a windowed mode window and its OpenGL context
window = glfwCreateWindow(1000, 800, "Font Test", NULL, NULL);
if(!window){
glfwTerminate();
return -1;
}
// Make the window's context current
glfwMakeContextCurrent(window);
glfwSwapInterval(1);
glfwSetKeyCallback(window, key_callback);
MyInitialize();
// Loop until the user closes the window
while(!glfwWindowShouldClose(window)){
// Render here
MyDisplay(window);
// Swap front and back buffers
glfwSwapBuffers(window);
// Poll for and process events
glfwPollEvents();
}
glfwDestroyWindow(window);
glfwTerminate();
return 0;
}
顶点着色器：
#version 330 core
layout (location = 0) in vec3 vertex;
layout (location = 1) in vec2 vertex_uv;
out vec2 uv;
void main(){
gl_Position = vec4(vertex.xyz, 1);
uv = vertex_uv;
}
片段着色器：
#version 330 core
in vec2 uv;
uniform vec4 color;
uniform sampler2D texture_sampler;
out vec4 color_out;
void main(){
color_out = vec4(1.0, 1.0, 1.0, texture(texture_sampler, uv).r) * color;
}