几乎完全重复的问题:OpenGL font rendering using Freetype2。
我正在尝试使用FreeType2(2.5.3)在我的OpenGL程序中渲染文本,基于本教程:http://en.wikibooks.org/wiki/OpenGL_Programming/Modern_OpenGL_Tutorial_Text_Rendering_02,使用与Bentebent在他的问题中所做的相同结构(上图)。
我遇到了同样的问题,即矩形显示而不是清晰可辨的字符(甚至使用GL_TEXTURE0
的正确glActiveTexture()
参数
例如,在其下方呈现绿色字符串"Hello"
和"World"
会给我这样的信息:
和Bentebent一样,使用gDebugger我可以看到我的纹理生成得很好。我已经搜索了google / stackoverflow,尝试了glTexImage2D
的不同参数,我片段着色器中color
的不同公式等,但没有运气。已经卡住了一段时间了。任何帮助表示赞赏。
用于创建纹理图集的结构:
//DrawTestOpenGLWnd.h
struct FontCharacter
{
float advanceX;
float advanceY;
float bitmapWidth;
float bitmapHeight;
float bitmapLeft;
float bitmapTop;
float uvOffsetX;
float uvOffsetY;
};
struct FontTextureAtlas
{
GLuint texture;
GLint textureUniform;
int width;
int height;
FontCharacter characters[128];
FontTextureAtlas(FT_Face face, int h, GLint tUniform)
{
FT_Set_Pixel_Sizes(face, 0, h);
FT_GlyphSlot glyphSlot = face->glyph;
int roww = 0;
int rowh = 0;
width = 0;
height = 0;
memset(characters, 0, sizeof(FontCharacter));
for (int i = 32; i < 128; i++)
{
if (FT_Load_Char(face, i, FT_LOAD_RENDER))
{
TRACE("Loading character %c failed\n", i);
continue;
}
if (roww + glyphSlot->bitmap.width + 1 >= MAX_WIDTH)
{
width = std::max(width, roww);
height += rowh;
roww = 0;
rowh = 0;
}
roww += glyphSlot->bitmap.width + 1;
rowh = std::max(rowh, glyphSlot->bitmap.rows);
}
width = std::max(width, roww);
height += rowh;
glGenTextures(1, &texture);
if (glGetError() != GL_NO_ERROR){
TRACE("glGenTextures failed\n");
}
glActiveTexture(GL_TEXTURE0);
if (glGetError() != GL_NO_ERROR){
TRACE("glActiveTexture failed\n");
}
glBindTexture(GL_TEXTURE_2D, texture);
if (glGetError() != GL_NO_ERROR){
TRACE("glBindTexture failed\n");
}
glUniform1i(tUniform, 0);
textureUniform = tUniform;
glTexImage2D(GL_TEXTURE_2D, 0, GL_R8, width, height, 0, GL_RED, GL_UNSIGNED_BYTE, 0);
if (glGetError() != GL_NO_ERROR){
TRACE("glTexImage2D failed\n");
}
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
if (glGetError() != GL_NO_ERROR){
TRACE("glPixelStorei failed\n");
}
glPixelStorei(GL_PACK_ALIGNMENT, 1);
if (glGetError() != GL_NO_ERROR){
TRACE("glPixelStorei failed\n");
}
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
if (glGetError() != GL_NO_ERROR){
TRACE("glTexParameteri failed\n");
}
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
if (glGetError() != GL_NO_ERROR){
TRACE("glTexParameteri failed\n");
}
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
if (glGetError() != GL_NO_ERROR){
TRACE("glTexParameteri failed\n");
}
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
if (glGetError() != GL_NO_ERROR){
TRACE("glTexParameteri failed\n");
}
int ox = 0;
int oy = 0;
rowh = 0;
for (int i = 32; i < 128; i++)
{
if (FT_Load_Char(face, i, FT_LOAD_RENDER)) {
TRACE("Loading character %c failed\n", i);
continue;
}
if (ox + glyphSlot->bitmap.width + 1 >= MAX_WIDTH) {
oy += rowh;
rowh = 0;
ox = 0;
}
glTexSubImage2D(GL_TEXTURE_2D, 0, ox, oy, glyphSlot->bitmap.width, glyphSlot->bitmap.rows, GL_RED, GL_UNSIGNED_BYTE, glyphSlot->bitmap.buffer);
if (glGetError() != GL_NO_ERROR) {
TRACE("BORKED AGAIN\n");
}
characters[i].advanceX = glyphSlot->advance.x >> 6;
characters[i].advanceY = glyphSlot->advance.y >> 6;
characters[i].bitmapWidth = glyphSlot->bitmap.width;
characters[i].bitmapHeight = glyphSlot->bitmap.rows;
characters[i].bitmapLeft = glyphSlot->bitmap_left;
characters[i].bitmapTop = glyphSlot->bitmap_top;
characters[i].uvOffsetX = ox / (float)width;
characters[i].uvOffsetY = oy / (float)height;
rowh = std::max(rowh, glyphSlot->bitmap.rows);
ox += glyphSlot->bitmap.width + 1;
}
TRACE("Generated a %d x %d (%d kb) texture atlas.\n", width, height, width * height / 1024);
}
~FontTextureAtlas()
{
glDeleteTextures(1, &texture);
}
};
InitFreeType函数:
void DrawTestOpenGLWnd::InitFreeType(char * strFontFilePath)
{
m_error = FT_Init_FreeType(&m_library);
if (m_error) {
TRACE("An error occurred during library initialization");
}
m_error = FT_New_Face(m_library, strFontFilePath, 0, &m_face);
if (m_error == FT_Err_Unknown_File_Format) {
TRACE("Font file could be opened and read, but it appears that its font format is unsupported");
}
else if (m_error) {
TRACE("Font file could not be opened or read. Or it's broken.");
}
m_program_text = LoadShaders("TextVertexShader.vertexshader", "TextFragmentShader.fragmentshader");
glUseProgram(m_program_text);
m_uniform_texture = glGetUniformLocation(m_program_text, "texture");
m_uniform_textColor = glGetUniformLocation(m_program_text, "textColor");
glGenVertexArrays(1, &vao_text);
glBindVertexArray(vao_text);
glGenBuffers(1, &vbo_text);
//glBindBuffer(GL_ARRAY_BUFFER, vbo_text);
a48 = new FontTextureAtlas(m_face, 48, m_uniform_texture);
a24 = new FontTextureAtlas(m_face, 24, m_uniform_texture);
a12 = new FontTextureAtlas(m_face, 12, m_uniform_texture);
}
RenderText函数:
void DrawTestOpenGLWnd::RenderText(char * text, FontTextureAtlas * atlas, float x, float y, float sx, float sy)
{
glUseProgram(m_program_text);
const unsigned char* p;
std::vector<glm::vec4> coords;
int c = 0;
for (p = (const unsigned char*)text; *p; p++)
{
float x2 = x + atlas->characters[*p].bitmapLeft * sx;
float y2 = -y - atlas->characters[*p].bitmapTop * sy;
float w = atlas->characters[*p].bitmapWidth * sx;
float h = atlas->characters[*p].bitmapHeight * sy;
x += atlas->characters[*p].advanceX * sx;
y += atlas->characters[*p].advanceY * sy;
if (!w || !h)
continue;
coords.push_back(
glm::vec4(
x2,
-y2,
atlas->characters[*p].uvOffsetX,
atlas->characters[*p].uvOffsetY)
);
coords.push_back(
glm::vec4(
x2 + w,
-y2,
atlas->characters[*p].uvOffsetX + atlas->characters[*p].bitmapWidth / atlas->width,
atlas->characters[*p].uvOffsetY)
);
coords.push_back(
glm::vec4(
x2,
-y2 - h,
atlas->characters[*p].uvOffsetX,
atlas->characters[*p].uvOffsetY + atlas->characters[*p].bitmapHeight / atlas->height)
);
coords.push_back(
glm::vec4(
x2 + w,
-y2,
atlas->characters[*p].uvOffsetX + atlas->characters[*p].bitmapWidth / atlas->width,
atlas->characters[*p].uvOffsetY)
);
coords.push_back(
glm::vec4(
x2,
-y2 - h,
atlas->characters[*p].uvOffsetX,
atlas->characters[*p].uvOffsetY + atlas->characters[*p].bitmapHeight / atlas->height)
);
coords.push_back(
glm::vec4(
x2 + w,
-y2 - h,
atlas->characters[*p].uvOffsetX + atlas->characters[*p].bitmapWidth / atlas->width,
atlas->characters[*p].uvOffsetY + atlas->characters[*p].bitmapHeight / atlas->height)
);
}
glBindVertexArray(vao_text);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glActiveTexture(GL_TEXTURE0);
glUniform1i(atlas->textureUniform, 0);
glBindTexture(GL_TEXTURE_2D, atlas->texture);
GLfloat textColor[4] = {0.0, 1.0, 0.0, 0.}; //green
glUniform4fv(m_uniform_textColor, 1, textColor);
glBindBuffer(GL_ARRAY_BUFFER, vbo_text);
glBufferData(GL_ARRAY_BUFFER, coords.size() * sizeof(glm::vec4), coords.data(), GL_DYNAMIC_DRAW);
//Position
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, sizeof(glm::vec4), (void*)0);
glDrawArrays(GL_TRIANGLES, 0, coords.size());
glDisableVertexAttribArray(0);
glBindVertexArray(0);
glUseProgram(0);
}
TextVertexShader.vertexshader:
#version 330 core
layout(location = 0) in vec4 pos_uv;
out vec2 uv;
void main(void) {
gl_Position = vec4(pos_uv.xy, 0, 1);
uv = pos_uv.zw;
}
TextFragmentShader.fragmentshader:
#version 330 core
in vec2 uv;
uniform sampler2D texture;
uniform vec4 textColor;
out vec4 color;
void main(void) {
color = vec4(textColor.rgb, texture2D(texture, uv).a);
}
答案 0 :(得分:4)
您的纹理格式为R8,因此它仅包含R通道。您的着色器接缝使用A通道。 比较这两行代码:
glTexImage2D(GL_TEXTURE_2D, 0, GL_R8, width, height, 0, GL_RED,
GL_UNSIGNED_BYTE, 0);
...
glTexSubImage2D(GL_TEXTURE_2D, 0, ox, oy, glyphSlot->bitmap.width,
glyphSlot->bitmap.rows, GL_RED, ...
VS
color = vec4(textColor.rgb, texture2D(texture, uv).a);
我建议更改GL_R8
&amp; GL_RED
至GL_ALPHA8
&amp; GL_ALPHA
如果你的OpenGL&lt; 3.0,否则将texture2D(texture, uv).a
更改为texture2D(texture, uv).r
。
答案 1 :(得分:3)
OP在这里。这是我的工作代码,根据Anonymous&#39;建议:
在struct FontCharacterAtlas中:
glTexImage2D(GL_TEXTURE_2D, 0, GL_RED, width, height, 0, GL_RED,
GL_UNSIGNED_BYTE, 0);
...
glTexSubImage2D(GL_TEXTURE_2D, 0, ox, oy, glyphSlot->bitmap.width, glyphSlot->bitmap.rows,
GL_RED, GL_UNSIGNED_BYTE, glyphSlot->bitmap.buffer);
在TextFragmentShader.fragmentshader中:
color = vec4(textColor.rgb, texture2D(texture, uv).r);
文字呈现,虽然不是很好(一些字符和边被略微剪掉,当使用a24或a12图集时字体非常混乱)但这是另一个故事。