Sign in to follow this  
swinchen

OpenGL OpenGL SDL_ttf font rendering problems.

Recommended Posts

Hello, I have been hacking at the SDL_ttf glfont.c example (included with the SDL_ttf source code) file in order to improve performance by pre-caching the ogl textures. As it stands right now it seems to render 'i' and 'l' correctly but all other glyphs show up as white or gray rectangles. Any help you might be able to offer would be greatly appreciated. I am not sure if this is an SDL problem I am having or an OpenGL... Here is the nice color coded version: http://paste.lisp.org/display/29373 Or see the attached code Thanks, Sam
#include <SDL/SDL.h>
#include <SDL/SDL_ttf.h>
#include <SDL/SDL_opengl.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>

#define PI 3.141592653589793238462643

typedef struct
{
	int minx, maxx, miny, maxy, advance;
	GLfloat texcoord[4];
	GLuint texid;
} t_glyph;

typedef struct
{
	int style, pointsize, height, ascent, descent, lineskip;
	SDL_Color color;
	t_glyph glyphs[128];
} t_font;

int build_font(char* filename, t_font* font);
void print_glstr(int x, int y, t_font* font, char* str);
void set_perspective(GLdouble fovy, GLdouble aspect, GLdouble zNear, GLdouble zFar);
void SDL_GL_Enter2DMode();
void SDL_GL_Leave2DMode();
static int power_of_two(int input);
GLuint SDL_GL_LoadTexture(SDL_Surface *surface, GLfloat *texcoord);

int main(int argc, char* argv[])
{
	t_font font;
	SDL_Surface* screen;
	
	SDL_Color white = {0xFF, 0xFF, 0xFF, 0x00};
	
	if ( SDL_Init(SDL_INIT_TIMER | SDL_INIT_VIDEO) < 0 )
	{
		fprintf(stderr, "ERROR Initializing SDL: %s\n", SDL_GetError());
		return -1;		
	}
	atexit(SDL_Quit);
	
	if ( TTF_Init() < 0 )
	{
		fprintf(stderr, "ERROR Initializing TTF Engine: %s\n", TTF_GetError());
		return -1;
	}
	atexit(TTF_Quit);
	
	SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
	screen = SDL_SetVideoMode(800, 600, 32, SDL_OPENGL);
	if ( screen == NULL )
	{
		fprintf(stderr, "ERROR Couldn't set video mode: %s\n", SDL_GetError());
		return -1;
	}
	
	glViewport(0, 0, screen->w, screen->h);
	glMatrixMode( GL_PROJECTION );
	glLoadIdentity();
	
	set_perspective(45.0f, (GLdouble) screen->w / screen->h, 1.0f, 100.0f);
	glEnable(GL_DEPTH_TEST);
	glDepthFunc(GL_LESS);
	glShadeModel(GL_SMOOTH);
	glClearColor(0.0, 0.0, 0.0, 1.0);
	
	
	font.pointsize = 20;
	font.style = TTF_STYLE_NORMAL;
	memcpy(&(font.color), &white, sizeof(SDL_Color));
	if ( build_font("MONACO.TTF",&font) < 0)
	{
		fprintf(stderr, "ERROR building font: %s\n", TTF_GetError());
		return -1;		
	}
	
	while ( SDL_GetTicks() < 5000 )
	{
		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
		
		glMatrixMode(GL_MODELVIEW);
		glLoadIdentity();
		glTranslated(0.0, 0.0, -5.0);
		
		glBegin(GL_POINTS);
			glVertex3d(0.0,0.0,0.0);
		glEnd();
		
		SDL_GL_Enter2DMode();
		print_glstr(100, 500, &font, "abcdefghijklmnopqrstuvwxyz");
		SDL_GL_Leave2DMode();		
			
		SDL_GL_SwapBuffers();
	}
	
	SDL_FreeSurface(screen);
	return 0;
}

int build_font(char* filename, t_font* font)
{
	TTF_Font* ttffont;
	SDL_Surface* surf;
	int i;
	GLenum gl_error;
	
	ttffont = TTF_OpenFont(filename, font->pointsize);
	if (ttffont == NULL)
	{
		TTF_SetError("ERROR opening font: %s\n", TTF_GetError());
		return -1;
	}
	
	TTF_SetFontStyle(ttffont, font->style);
	
	font->ascent = TTF_FontAscent(ttffont);
	font->descent = TTF_FontDescent(ttffont);
	font->height = TTF_FontHeight(ttffont);
	font->lineskip = TTF_FontLineSkip(ttffont);
	
	for ( i = ' '; i <= '~'; i++ )
	{
		surf = TTF_RenderGlyph_Blended(ttffont, i, font->color);
		if ( surf == NULL )
		{
			TTF_SetError("ERROR rendering glyph %c: %s\n", (char)i,
				TTF_GetError());
			TTF_CloseFont(ttffont);
			return -1;			
		}
		
		TTF_GlyphMetrics(ttffont, i, &(font->glyphs[i].minx), 
			&(font->glyphs[i].maxx), &(font->glyphs[i].miny),
			&(font->glyphs[i].maxy), &(font->glyphs[i].advance));
		
		font->glyphs[i].texid = SDL_GL_LoadTexture(surf,
			font->glyphs[i].texcoord);
		
		if ( (gl_error = glGetError()) != GL_NO_ERROR ) {
			/* If this failed, the text may exceed texture size limits */
			TTF_SetError("Warning: Couldn't create texture: 0x%x\n", gl_error);
			SDL_FreeSurface(surf);
			TTF_CloseFont(ttffont);
			return -1;
		}		
		SDL_FreeSurface(surf);
	}
	
	TTF_CloseFont(ttffont);
	return 0;
}

void print_glstr(int x, int y, t_font* font, char* str)
{
	int texMinX, texMaxX, texMinY, texMaxY, i, w, h;
	
	while (*str != 0)
	{
		i = (int)*str;
		texMinX = font->glyphs[i].texcoord[0];
		texMinY = font->glyphs[i].texcoord[1];
		texMaxX = font->glyphs[i].texcoord[2];
		texMaxY = font->glyphs[i].texcoord[3];
		w = font->glyphs[i].maxx;
		h = font->glyphs[i].maxy;
		
		glBindTexture(GL_TEXTURE_2D, font->glyphs[i].texid);
		glBegin(GL_TRIANGLE_STRIP);
			glTexCoord2f(texMinX, texMinY); glVertex2i(x,   y  );
			glTexCoord2f(texMaxX, texMinY); glVertex2i(x+w, y  );
			glTexCoord2f(texMinX, texMaxY); glVertex2i(x,   y+h);
			glTexCoord2f(texMaxX, texMaxY); glVertex2i(x+w, y+h);
		glEnd();
		
		x += font->glyphs[i].advance;
		str++;
	}
}

void set_perspective(GLdouble fovy, GLdouble aspect, GLdouble zNear, GLdouble zFar)
{
   GLdouble ymax;
   ymax = zNear * tan(fovy * PI / 360.0f);
   glFrustum(-ymax*aspect, ymax*aspect, -ymax, ymax, zNear, zFar);
}

void SDL_GL_Enter2DMode()
{
	SDL_Surface *screen = SDL_GetVideoSurface();

	/* Note, there may be other things you need to change,
	   depending on how you have your OpenGL state set up.
	*/
	glPushAttrib(GL_ENABLE_BIT);
	glDisable(GL_DEPTH_TEST);
	glDisable(GL_CULL_FACE);
	glEnable(GL_TEXTURE_2D);

	/* This allows alpha blending of 2D textures with the scene */
	glEnable(GL_BLEND);
	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

	glViewport(0, 0, screen->w, screen->h);

	glMatrixMode(GL_PROJECTION);
	glPushMatrix();
	glLoadIdentity();

	glOrtho(0.0, (GLdouble)screen->w, (GLdouble)screen->h, 0.0, 0.0, 1.0);

	glMatrixMode(GL_MODELVIEW);
	glPushMatrix();
	glLoadIdentity();

	glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
}

void SDL_GL_Leave2DMode()
{
	glMatrixMode(GL_MODELVIEW);
	glPopMatrix();

	glMatrixMode(GL_PROJECTION);
	glPopMatrix();

	glPopAttrib();
}

/* Quick utility function for texture creation */
static int power_of_two(int input)
{
	int value = 1;

	while ( value < input ) {
		value <<= 1;
	}
	return value;
}

GLuint SDL_GL_LoadTexture(SDL_Surface *surface, GLfloat *texcoord)
{
	GLuint texture;
	int w, h;
	SDL_Surface *image;
	SDL_Rect area;
	Uint32 saved_flags;
	Uint8  saved_alpha;

	/* Use the surface width and height expanded to powers of 2 */
	w = power_of_two(surface->w);
	h = power_of_two(surface->h);
	texcoord[0] = 0.0f;			/* Min X */
	texcoord[1] = 0.0f;			/* Min Y */
	texcoord[2] = (GLfloat)surface->w / w;	/* Max X */
	texcoord[3] = (GLfloat)surface->h / h;	/* Max Y */

	image = SDL_CreateRGBSurface(
			SDL_SWSURFACE,
			w, h,
			32,
#if SDL_BYTEORDER == SDL_LIL_ENDIAN /* OpenGL RGBA masks */
			0x000000FF, 
			0x0000FF00, 
			0x00FF0000, 
			0xFF000000
#else
			0xFF000000,
			0x00FF0000, 
			0x0000FF00, 
			0x000000FF
#endif
		       );
	if ( image == NULL ) {
		return 0;
	}

	/* Save the alpha blending attributes */
	saved_flags = surface->flags&(SDL_SRCALPHA|SDL_RLEACCELOK);
	saved_alpha = surface->format->alpha;
	if ( (saved_flags & SDL_SRCALPHA) == SDL_SRCALPHA ) {
		SDL_SetAlpha(surface, 0, 0);
	}

	/* Copy the surface into the GL texture image */
	area.x = 0;
	area.y = 0;
	area.w = surface->w;
	area.h = surface->h;
	SDL_BlitSurface(surface, &area, image, &area);

	/* Restore the alpha blending attributes */
	if ( (saved_flags & SDL_SRCALPHA) == SDL_SRCALPHA ) {
		SDL_SetAlpha(surface, saved_flags, saved_alpha);
	}

	/* Create an OpenGL texture for the image */
	glGenTextures(1, &texture);
	glBindTexture(GL_TEXTURE_2D, texture);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
	glTexImage2D(GL_TEXTURE_2D,
		     0,
		     GL_RGBA,
		     w, h,
		     0,
		     GL_RGBA,
		     GL_UNSIGNED_BYTE,
		     image->pixels);
	SDL_FreeSurface(image); /* No longer needed */

	return texture;
}


Share this post


Link to post
Share on other sites
Hmmm, if no one sees the problem right away maybe you could give me some tips on debugging applications with OpenGL? If I used a software renderer like MESA maybe I could use traditional debugging techniques? Right now I am staring at the code saying "Well, it looks like it should work!"


Thanks,
Sam

Share this post


Link to post
Share on other sites
In print_glstr function set w to font->glyphs[i].advance and h to font->height,
since maxx and maxy don't give glyph width and height. Another possibility is the call to TTF_RenderGlyph_Blended. Replace it with TTF_RenderGlyph_Solid.

I would also suggest putting all glyphs in one big OpenGL texture. Something like in NeHe tutorial #17 (textured fonts).

Share this post


Link to post
Share on other sites
Guest Anonymous Poster
Doh! I figured it out. In the print_glstr function I declared texMinX and friends as int... they should have been GLfloat. Also, I fixed the font alignment...

Now you mentioned using one texture to hold all of the font information. What are the reasons/benefits of doing this?

If I did store them as one texture I could just render one surface that contains all printable characters, and then "chop" the texture into display lists using the glyph metrics correct?

Thanks!

Sam


#include <SDL/SDL.h>
#include <SDL/SDL_ttf.h>
#include <GL/glew.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <limits.h>

#define PI 3.141592653589793238462643

typedef struct
{
int minx, maxx, miny, maxy, advance;
GLfloat texcoord[4];
GLuint texid;
} t_glyph;

typedef struct
{
int style, pointsize, height, ascent, descent, lineskip;
SDL_Color color;
t_glyph glyphs[128];
} t_font;

int build_font(char* filename, t_font* font);
void print_glstr(int x, int y, t_font* font, char* str);
void set_perspective(GLdouble fovy, GLdouble aspect, GLdouble zNear, GLdouble zFar);
void SDL_GL_Enter2DMode();
void SDL_GL_Leave2DMode();
static int power_of_two(int input);
GLuint SDL_GL_LoadTexture(SDL_Surface *surface, GLfloat *texcoord);

int main(int argc, char* argv[])
{
t_font font;
SDL_Surface* screen;
GLenum glerr;
char buffer[256];
unsigned int frame_cnt, old_ticks;
GLfloat frame_rate;

SDL_Color white = {0xFF, 0xFF, 0xFF, 0x00};

if ( SDL_Init(SDL_INIT_TIMER | SDL_INIT_VIDEO) < 0 )
{
fprintf(stderr, "ERROR Initializing SDL: %s\n", SDL_GetError());
return -1;
}
atexit(SDL_Quit);

SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
screen = SDL_SetVideoMode(1024, 768, 32, SDL_OPENGL | SDL_FULLSCREEN);
if ( screen == NULL )
{
fprintf(stderr, "ERROR Couldn't set video mode: %s\n", SDL_GetError());
return -1;
}

SDL_WM_SetCaption("Sam's Font Example", 0);

if ( TTF_Init() < 0 )
{
fprintf(stderr, "ERROR Initializing TTF Engine: %s\n", TTF_GetError());
return -1;
}
atexit(TTF_Quit);

glerr = glewInit();
if ( glerr != GLEW_OK )
{
fprintf(stderr, "ERROR Initializing GLEW: %s\n", glewGetErrorString(glerr));
return -1;
}

glViewport(0, 0, screen->w, screen->h);
glMatrixMode( GL_PROJECTION );
glLoadIdentity();

set_perspective(45.0f, (GLdouble) screen->w / screen->h, 1.0f, 1000.0f);

glMatrixMode( GL_MODELVIEW );
glLoadIdentity( );
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LESS);
glShadeModel(GL_SMOOTH);

font.pointsize = 20;
font.style = TTF_STYLE_NORMAL;
memcpy(&(font.color), &white, sizeof(SDL_Color));
if ( build_font(argv[1],&font) < 0 )
{
fprintf(stderr, "ERROR building font: %s\n", TTF_GetError());
return -1;
}

frame_cnt = 0;
old_ticks = SDL_GetTicks();
frame_rate = 0.0;
while ( SDL_GetTicks() < 10000 )
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();

glTranslated(0.0, 0.0, -5.0);

SDL_GL_Enter2DMode();

sprintf(buffer, "Frame Rate - %f", frame_rate);
print_glstr(0, font.height, &font, buffer);

// print_glstr(0, 100, &font, " !\"#$%&'()*+,-./0123456789:;<=>?@");
// print_glstr(0, 200, &font, "ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`");
// print_glstr(0, 300, &font, "abcdefghijklmnopqrstuvwxyz{|}~");

SDL_GL_Leave2DMode();
SDL_GL_SwapBuffers();

frame_cnt++;

if (frame_cnt >= 100)
{
frame_rate = (GLfloat)frame_cnt/((GLfloat)(SDL_GetTicks() - old_ticks)/1000.0f);
old_ticks = SDL_GetTicks();
frame_cnt = 0;
}
}

SDL_FreeSurface(screen);
return 0;
}

int build_font(char* filename, t_font* font)
{
TTF_Font* ttffont;
SDL_Surface* surf;
int i;
GLenum gl_error;

ttffont = TTF_OpenFont(filename, font->pointsize);
if (ttffont == NULL)
{
TTF_SetError("ERROR opening font: %s\n", TTF_GetError());
return -1;
}

TTF_SetFontStyle(ttffont, font->style);

font->ascent = TTF_FontAscent(ttffont);
font->descent = TTF_FontDescent(ttffont);
font->height = TTF_FontHeight(ttffont);
font->lineskip = TTF_FontLineSkip(ttffont);

for ( i = ' '; i <= '~'; i++ )
{
surf = TTF_RenderGlyph_Blended(ttffont, i, font->color);
if ( surf == NULL )
{
TTF_SetError("ERROR rendering glyph %c: %s\n", (char)i,
TTF_GetError());
TTF_CloseFont(ttffont);
return -1;
}

TTF_GlyphMetrics(ttffont, i, &(font->glyphs[i].minx),
&(font->glyphs[i].maxx), &(font->glyphs[i].miny),
&(font->glyphs[i].maxy), &(font->glyphs[i].advance));

font->glyphs[i].texid = SDL_GL_LoadTexture(surf,
font->glyphs[i].texcoord);

if ( (gl_error = glGetError()) != GL_NO_ERROR ) {
/* If this failed, the text may exceed texture size limits */
TTF_SetError("Warning: Couldn't create texture: 0x%x\n", gl_error);
SDL_FreeSurface(surf);
TTF_CloseFont(ttffont);
return -1;
}
SDL_FreeSurface(surf);
}

TTF_CloseFont(ttffont);
return 0;
}

void print_glstr(int x, int y, t_font* font, char* str)
{
GLfloat texMinX, texMaxX, texMinY, texMaxY;
GLfloat left, right, top, bottom;
t_glyph* g;

while (*str != 0)
{
g = &(font->glyphs[(int)*str]);

texMinX = g->texcoord[0];
texMinY = g->texcoord[1];
texMaxX = g->texcoord[2];
texMaxY = g->texcoord[3];
left = x + g->minx;
right = x + g->maxx - g->minx;
top = y - g->maxy;
bottom = y - g->miny;

glBindTexture(GL_TEXTURE_2D, g->texid);
glBegin(GL_TRIANGLE_STRIP);
glTexCoord2f(texMinX, texMinY); glVertex2f( left, top);
glTexCoord2f(texMaxX, texMinY); glVertex2f(right, top);
glTexCoord2f(texMinX, texMaxY); glVertex2f( left, bottom);
glTexCoord2f(texMaxX, texMaxY); glVertex2f(right, bottom);
glEnd();

x += g->advance;
str++;
}
}

void set_perspective(GLdouble fovy, GLdouble aspect, GLdouble zNear, GLdouble zFar)
{
GLdouble ymax;
ymax = zNear * tan(fovy * PI / 360.0f);
glFrustum(-ymax*aspect, ymax*aspect, -ymax, ymax, zNear, zFar);
}

void SDL_GL_Enter2DMode()
{
SDL_Surface *screen = SDL_GetVideoSurface();

/* Note, there may be other things you need to change,
depending on how you have your OpenGL state set up.
*/

glPushAttrib(GL_ALL_ATTRIB_BITS);
glDisable(GL_DEPTH_TEST);
glDisable(GL_CULL_FACE);
glEnable(GL_TEXTURE_2D);

/* This allows alpha blending of 2D textures with the scene */
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

glViewport(0, 0, screen->w, screen->h);

glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();

glOrtho(0.0, (GLdouble)screen->w, (GLdouble)screen->h, 0.0, 0.0, 1.0);

glMatrixMode(GL_MODELVIEW);
glPushMatrix();
glLoadIdentity();

glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
}

void SDL_GL_Leave2DMode()
{
glMatrixMode(GL_MODELVIEW);
glPopMatrix();

glMatrixMode(GL_PROJECTION);
glPopMatrix();

glPopAttrib();
}

/* Quick utility function for texture creation */
static int power_of_two(int input)
{
int value = 1;

while ( value < input ) {
value <<= 1;
}
return value;
}

GLuint SDL_GL_LoadTexture(SDL_Surface *surface, GLfloat *texcoord)
{
GLuint texture;
int w, h;
SDL_Surface *image;
SDL_Rect area;
Uint32 saved_flags;
Uint8 saved_alpha;

/* Use the surface width and height expanded to powers of 2 */
w = power_of_two(surface->w);
h = power_of_two(surface->h);
texcoord[0] = 0.0f; /* Min X */
texcoord[1] = 0.0f; /* Min Y */
texcoord[2] = (GLfloat)surface->w / w; /* Max X */
texcoord[3] = (GLfloat)surface->h / h; /* Max Y */

image = SDL_CreateRGBSurface(
SDL_SWSURFACE,
w, h,
32,
#if SDL_BYTEORDER == SDL_LIL_ENDIAN /* OpenGL RGBA masks */
0x000000FF,
0x0000FF00,
0x00FF0000,
0xFF000000
#else
0xFF000000,
0x00FF0000,
0x0000FF00,
0x000000FF
#endif
);
if ( image == NULL ) {
return 0;
}

/* Save the alpha blending attributes */
saved_flags = surface->flags&(SDL_SRCALPHA|SDL_RLEACCELOK);
saved_alpha = surface->format->alpha;
if ( (saved_flags & SDL_SRCALPHA) == SDL_SRCALPHA ) {
SDL_SetAlpha(surface, 0, 0);
}

/* Copy the surface into the GL texture image */
area.x = 0;
area.y = 0;
area.w = surface->w;
area.h = surface->h;
SDL_BlitSurface(surface, &area, image, &area);

/* Restore the alpha blending attributes */
if ( (saved_flags & SDL_SRCALPHA) == SDL_SRCALPHA ) {
SDL_SetAlpha(surface, saved_flags, saved_alpha);
}

/* Create an OpenGL texture for the image */
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexImage2D(GL_TEXTURE_2D,
0,
GL_RGBA,
w, h,
0,
GL_RGBA,
GL_UNSIGNED_BYTE,
image->pixels);
SDL_FreeSurface(image); /* No longer needed */

return texture;
}

Share this post


Link to post
Share on other sites
Doh! I figured it out. In the print_glstr function I declared texMinX and friends as int... they should have been GLfloat. Also, I fixed the font alignment...

Now you mentioned using one texture to hold all of the font information. What are the reasons/benefits of doing this?

If I did store them as one texture I could just render one surface that contains all printable characters, and then "chop" the texture into display lists using the glyph metrics correct?

Thanks!

Sam


#include <SDL/SDL.h>
#include <SDL/SDL_ttf.h>
#include <GL/glew.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <limits.h>

#define PI 3.141592653589793238462643

typedef struct
{
int minx, maxx, miny, maxy, advance;
GLfloat texcoord[4];
GLuint texid;
} t_glyph;

typedef struct
{
int style, pointsize, height, ascent, descent, lineskip;
SDL_Color color;
t_glyph glyphs[128];
} t_font;

int build_font(char* filename, t_font* font);
void print_glstr(int x, int y, t_font* font, char* str);
void set_perspective(GLdouble fovy, GLdouble aspect, GLdouble zNear, GLdouble zFar);
void SDL_GL_Enter2DMode();
void SDL_GL_Leave2DMode();
static int power_of_two(int input);
GLuint SDL_GL_LoadTexture(SDL_Surface *surface, GLfloat *texcoord);

int main(int argc, char* argv[])
{
t_font font;
SDL_Surface* screen;
GLenum glerr;
char buffer[256];
unsigned int frame_cnt, old_ticks;
GLfloat frame_rate;

SDL_Color white = {0xFF, 0xFF, 0xFF, 0x00};

if ( SDL_Init(SDL_INIT_TIMER | SDL_INIT_VIDEO) < 0 )
{
fprintf(stderr, "ERROR Initializing SDL: %s\n", SDL_GetError());
return -1;
}
atexit(SDL_Quit);

SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
screen = SDL_SetVideoMode(1024, 768, 32, SDL_OPENGL | SDL_FULLSCREEN);
if ( screen == NULL )
{
fprintf(stderr, "ERROR Couldn't set video mode: %s\n", SDL_GetError());
return -1;
}

SDL_WM_SetCaption("Sam's Font Example", 0);

if ( TTF_Init() < 0 )
{
fprintf(stderr, "ERROR Initializing TTF Engine: %s\n", TTF_GetError());
return -1;
}
atexit(TTF_Quit);

glerr = glewInit();
if ( glerr != GLEW_OK )
{
fprintf(stderr, "ERROR Initializing GLEW: %s\n", glewGetErrorString(glerr));
return -1;
}

glViewport(0, 0, screen->w, screen->h);
glMatrixMode( GL_PROJECTION );
glLoadIdentity();

set_perspective(45.0f, (GLdouble) screen->w / screen->h, 1.0f, 1000.0f);

glMatrixMode( GL_MODELVIEW );
glLoadIdentity( );
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LESS);
glShadeModel(GL_SMOOTH);

font.pointsize = 20;
font.style = TTF_STYLE_NORMAL;
memcpy(&(font.color), &white, sizeof(SDL_Color));
if ( build_font(argv[1],&font) < 0 )
{
fprintf(stderr, "ERROR building font: %s\n", TTF_GetError());
return -1;
}

frame_cnt = 0;
old_ticks = SDL_GetTicks();
frame_rate = 0.0;
while ( SDL_GetTicks() < 10000 )
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();

glTranslated(0.0, 0.0, -5.0);

SDL_GL_Enter2DMode();

sprintf(buffer, "Frame Rate - %f", frame_rate);
print_glstr(0, font.height, &font, buffer);

// print_glstr(0, 100, &font, " !\"#$%&'()*+,-./0123456789:;<=>?@");
// print_glstr(0, 200, &font, "ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`");
// print_glstr(0, 300, &font, "abcdefghijklmnopqrstuvwxyz{|}~");

SDL_GL_Leave2DMode();
SDL_GL_SwapBuffers();

frame_cnt++;

if (frame_cnt >= 100)
{
frame_rate = (GLfloat)frame_cnt/((GLfloat)(SDL_GetTicks() - old_ticks)/1000.0f);
old_ticks = SDL_GetTicks();
frame_cnt = 0;
}
}

SDL_FreeSurface(screen);
return 0;
}

int build_font(char* filename, t_font* font)
{
TTF_Font* ttffont;
SDL_Surface* surf;
int i;
GLenum gl_error;

ttffont = TTF_OpenFont(filename, font->pointsize);
if (ttffont == NULL)
{
TTF_SetError("ERROR opening font: %s\n", TTF_GetError());
return -1;
}

TTF_SetFontStyle(ttffont, font->style);

font->ascent = TTF_FontAscent(ttffont);
font->descent = TTF_FontDescent(ttffont);
font->height = TTF_FontHeight(ttffont);
font->lineskip = TTF_FontLineSkip(ttffont);

for ( i = ' '; i <= '~'; i++ )
{
surf = TTF_RenderGlyph_Blended(ttffont, i, font->color);
if ( surf == NULL )
{
TTF_SetError("ERROR rendering glyph %c: %s\n", (char)i,
TTF_GetError());
TTF_CloseFont(ttffont);
return -1;
}

TTF_GlyphMetrics(ttffont, i, &(font->glyphs[i].minx),
&(font->glyphs[i].maxx), &(font->glyphs[i].miny),
&(font->glyphs[i].maxy), &(font->glyphs[i].advance));

font->glyphs[i].texid = SDL_GL_LoadTexture(surf,
font->glyphs[i].texcoord);

if ( (gl_error = glGetError()) != GL_NO_ERROR ) {
/* If this failed, the text may exceed texture size limits */
TTF_SetError("Warning: Couldn't create texture: 0x%x\n", gl_error);
SDL_FreeSurface(surf);
TTF_CloseFont(ttffont);
return -1;
}
SDL_FreeSurface(surf);
}

TTF_CloseFont(ttffont);
return 0;
}

void print_glstr(int x, int y, t_font* font, char* str)
{
GLfloat texMinX, texMaxX, texMinY, texMaxY;
GLfloat left, right, top, bottom;
t_glyph* g;

while (*str != 0)
{
g = &(font->glyphs[(int)*str]);

texMinX = g->texcoord[0];
texMinY = g->texcoord[1];
texMaxX = g->texcoord[2];
texMaxY = g->texcoord[3];
left = x + g->minx;
right = x + g->maxx - g->minx;
top = y - g->maxy;
bottom = y - g->miny;

glBindTexture(GL_TEXTURE_2D, g->texid);
glBegin(GL_TRIANGLE_STRIP);
glTexCoord2f(texMinX, texMinY); glVertex2f( left, top);
glTexCoord2f(texMaxX, texMinY); glVertex2f(right, top);
glTexCoord2f(texMinX, texMaxY); glVertex2f( left, bottom);
glTexCoord2f(texMaxX, texMaxY); glVertex2f(right, bottom);
glEnd();

x += g->advance;
str++;
}
}

void set_perspective(GLdouble fovy, GLdouble aspect, GLdouble zNear, GLdouble zFar)
{
GLdouble ymax;
ymax = zNear * tan(fovy * PI / 360.0f);
glFrustum(-ymax*aspect, ymax*aspect, -ymax, ymax, zNear, zFar);
}

void SDL_GL_Enter2DMode()
{
SDL_Surface *screen = SDL_GetVideoSurface();

/* Note, there may be other things you need to change,
depending on how you have your OpenGL state set up.
*/

glPushAttrib(GL_ALL_ATTRIB_BITS);
glDisable(GL_DEPTH_TEST);
glDisable(GL_CULL_FACE);
glEnable(GL_TEXTURE_2D);

/* This allows alpha blending of 2D textures with the scene */
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

glViewport(0, 0, screen->w, screen->h);

glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();

glOrtho(0.0, (GLdouble)screen->w, (GLdouble)screen->h, 0.0, 0.0, 1.0);

glMatrixMode(GL_MODELVIEW);
glPushMatrix();
glLoadIdentity();

glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
}

void SDL_GL_Leave2DMode()
{
glMatrixMode(GL_MODELVIEW);
glPopMatrix();

glMatrixMode(GL_PROJECTION);
glPopMatrix();

glPopAttrib();
}

/* Quick utility function for texture creation */
static int power_of_two(int input)
{
int value = 1;

while ( value < input ) {
value <<= 1;
}
return value;
}

GLuint SDL_GL_LoadTexture(SDL_Surface *surface, GLfloat *texcoord)
{
GLuint texture;
int w, h;
SDL_Surface *image;
SDL_Rect area;
Uint32 saved_flags;
Uint8 saved_alpha;

/* Use the surface width and height expanded to powers of 2 */
w = power_of_two(surface->w);
h = power_of_two(surface->h);
texcoord[0] = 0.0f; /* Min X */
texcoord[1] = 0.0f; /* Min Y */
texcoord[2] = (GLfloat)surface->w / w; /* Max X */
texcoord[3] = (GLfloat)surface->h / h; /* Max Y */

image = SDL_CreateRGBSurface(
SDL_SWSURFACE,
w, h,
32,
#if SDL_BYTEORDER == SDL_LIL_ENDIAN /* OpenGL RGBA masks */
0x000000FF,
0x0000FF00,
0x00FF0000,
0xFF000000
#else
0xFF000000,
0x00FF0000,
0x0000FF00,
0x000000FF
#endif
);
if ( image == NULL ) {
return 0;
}

/* Save the alpha blending attributes */
saved_flags = surface->flags&(SDL_SRCALPHA|SDL_RLEACCELOK);
saved_alpha = surface->format->alpha;
if ( (saved_flags & SDL_SRCALPHA) == SDL_SRCALPHA ) {
SDL_SetAlpha(surface, 0, 0);
}

/* Copy the surface into the GL texture image */
area.x = 0;
area.y = 0;
area.w = surface->w;
area.h = surface->h;
SDL_BlitSurface(surface, &area, image, &area);

/* Restore the alpha blending attributes */
if ( (saved_flags & SDL_SRCALPHA) == SDL_SRCALPHA ) {
SDL_SetAlpha(surface, saved_flags, saved_alpha);
}

/* Create an OpenGL texture for the image */
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexImage2D(GL_TEXTURE_2D,
0,
GL_RGBA,
w, h,
0,
GL_RGBA,
GL_UNSIGNED_BYTE,
image->pixels);
SDL_FreeSurface(image); /* No longer needed */

return texture;
}

Share this post


Link to post
Share on other sites
Quote:

If I did store them as one texture I could just render one surface that contains all printable characters, and then "chop" the texture into display lists using the glyph metrics correct?

Exactly. Also you call glBindTexture only once - for whole printed string and not for each char.

I know very little about OpenGL texture management but I believe that it is better to use one big texture then lots of small ones.

Share this post


Link to post
Share on other sites
Alright thanks. I can render all printable characters, but in order to make my life easier I am trying to draw lines and points while in SDL_GL_Enter2DMode(); (you know, just so I can see if I am chopping at the right point) but I can not draw anything while in 2D mode. Do you know any reason why I wouldn't be able to? Thanks,

Sam

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this