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  • OpenGL font rendering

    - by DEElekgolo
    I am trying to make an openGL text rendering class using FreeType. I was originally following this code but it doesn't seem to work out for me. I get nothing reguardless of what parameters I put for Draw(). class Font { public: Font() { if (FT_Init_FreeType(&ftLibrary)) { printf("Could not initialize FreeType library\n"); return; } glGenBuffers(1,&iVerts); } bool Load(std::string sFont, unsigned int Size = 12.0f) { if (FT_New_Face(ftLibrary,sFont.c_str(),0,&ftFace)) { printf("Could not open font: %s\n",sFont.c_str()); return true; } iSize = Size; FT_Set_Pixel_Sizes(ftFace,0,(int)iSize); FT_GlyphSlot gGlyph = ftFace->glyph; //Generating the texture atlas. //Rather than some amazing rectangular packing method, I'm just going //to have one long strip of letters with the height being that of the font size. int width = 0; int height = 0; for (int i = 32; i < 128; i++) { if (FT_Load_Char(ftFace,i,FT_LOAD_RENDER)) { printf("Error rendering letter %c for font %s.\n",i,sFont.c_str()); } width += gGlyph->bitmap.width; height += std::max(height,gGlyph->bitmap.rows); } //Generate the openGL texture glActiveTexture(GL_TEXTURE0); //if I texture exists then delete it. iTexture ? glDeleteBuffers(1,&iTexture):0; glGenTextures(1,&iTexture); glBindTexture(GL_TEXTURE_2D,iTexture); glPixelStorei(GL_UNPACK_ALIGNMENT,1); glTexImage2D(GL_TEXTURE_2D,0,GL_ALPHA,width,height,0,GL_ALPHA,GL_UNSIGNED_BYTE,0); 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); //load the glyphs and set the glyph data int x = 0; for (int i = 32; i < 128; i++) { if (FT_Load_Char(ftFace,i,FT_LOAD_RENDER)) { //if it cant load the character continue; } //load the glyph map into the texture glTexSubImage2D(GL_TEXTURE_2D,0,x,0, gGlyph->bitmap.width, gGlyph->bitmap.rows, GL_ALPHA, GL_UNSIGNED_BYTE, gGlyph->bitmap.buffer); //move the "pen" down the strip x += gGlyph->bitmap.width; chars[i].ax = (float)(gGlyph->advance.x >> 6); chars[i].ay = (float)(gGlyph->advance.y >> 6); chars[i].bw = (float)gGlyph->bitmap.width; chars[i].bh = (float)gGlyph->bitmap.rows; chars[i].bl = (float)gGlyph->bitmap_left; chars[i].bt = (float)gGlyph->bitmap_top; chars[i].tx = (float)x/width; } printf("Loaded font: %s\n",sFont.c_str()); return true; } void Draw(std::string sString,Vector2f vPos = Vector2f(0,0),Vector2f vScale = Vector2f(1,1)) { struct pPoint { pPoint() { x = y = s = t = 0; } pPoint(float a,float b,float c,float d) { x = a; y = b; s = c; t = d; } float x,y; float s,t; }; pPoint* cCoordinates = new pPoint[6*sString.length()]; int n = 0; for (const char *p = sString.c_str(); *p; p++) { float x2 = vPos.x() + chars[*p].bl * vScale.x(); float y2 = -vPos.y() - chars[*p].bt * vScale.y(); float w = chars[*p].bw * vScale.x(); float h = chars[*p].bh * vScale.y(); float x = vPos.x() + chars[*p].ax * vScale.x(); float y = vPos.y() + chars[*p].ay * vScale.y(); //skip characters with no pixels //still advances though if (!w || !h) { continue; } //triangle one cCoordinates[n++] = pPoint( x2 , -y2 , chars[*p].tx , 0); cCoordinates[n++] = pPoint( x2+w , -y2 , chars[*p].tx + chars[*p].bw / w , 0); cCoordinates[n++] = pPoint( x2 , -y2-h , chars[*p].tx , chars[*p].bh / h); cCoordinates[n++] = pPoint( x2+w , -y2 , chars[*p].tx + chars[*p].bw / w , 0); cCoordinates[n++] = pPoint( x2 , -y2-h , chars[*p].tx , chars[*p].bh / h); cCoordinates[n++] = pPoint( x2+w , -y2-h , chars[*p].tx + chars[*p].bw / w , chars[*p].bh / h); } glBindBuffer(GL_ARRAY_BUFFER,iVerts); glBindBuffer(GL_TEXTURE_2D,iTexture); //Vertices glEnableClientState(GL_VERTEX_ARRAY); glVertexPointer(2,GL_FLOAT,sizeof(pPoint),&cCoordinates[0].x); //TexCoord 0 glClientActiveTexture(GL_TEXTURE0); glEnableClientState(GL_TEXTURE_COORD_ARRAY); glTexCoordPointer(2,GL_FLOAT,sizeof(pPoint),&cCoordinates[0].s); glCullFace(GL_NONE); glBufferData(GL_ARRAY_BUFFER,6*sString.length(),cCoordinates,GL_DYNAMIC_DRAW); glDrawArrays(GL_TRIANGLES,0,n); glCullFace(GL_BACK); glBindBuffer(GL_ARRAY_BUFFER,0); glBindBuffer(GL_TEXTURE_2D,0); glDisableClientState(GL_VERTEX_ARRAY); glDisableClientState(GL_TEXTURE_COORD_ARRAY); } ~Font() { glDeleteBuffers(1,&iVerts); glDeleteBuffers(1,&iTexture); } private: unsigned int iSize; //openGL texture atlas unsigned int iTexture; //openGL geometry buffer; unsigned int iVerts; FT_Library ftLibrary; FT_Face ftFace; struct Character { float ax,ay;//Advance float bw,bh;//bitmap size float bl,bt;//bitmap left and top float tx; } chars[128]; };

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