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OpenGL Using text in OpenGL

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I'm writing a simple game engine for openGL and i'm having some issues on text. I did some research on the subject, and i was able to implement the bitmap text algrathm from NEHE's Opengl tortutial, but it only works for a blank screen(ie, when there is no 3d drawing being done) Here's my code for drawing the scene(note, the everything up to this point has been initalized, including the buildfont and i've currently put the text output code at the bottom)
int DrawGLScene(GLvoid)									// Here's Where We Do All The Drawing
{
	//bool once = false;  //used for old movement st
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);	// Clear The Screen And The Depth Buffer
	glLoadIdentity();									// Reset The View

	clock_t time_elapsed;
 time_elapsed = clock();
	GLfloat x_m, y_m, z_m, u_m, v_m;
	GLfloat xtrans = -xpos;
	GLfloat ztrans = -zpos;
	GLfloat ytrans = -headbob-0.4f;
	GLfloat sceneroty = 360.0f - yrot;

	int numpolygons;
 // if (once) //old movement style
 // {
	//glRotatef(lookupdown,1.0f,0,0);//rotates scene up and down
	//glRotatef(sceneroty,0,1.0f,0);//rotates scene right and left 


	//glTranslatef(xtrans, ytrans, ztrans);//moves the scene to simulate camera movement
 // //once = false;
 // }
	

glLoadIdentity();
  gluLookAt( -xtrans, -ytrans, -ztrans, 
	     -xtrans-sin(yrot*piover180)*100,-tan(lookupdown*piover180)*100, -ztrans-cos(yrot*piover180)*100, 
	     0.0, 1.0, 0.0);

	


glEnable(GL_TEXTURE_2D);
	glBindTexture(GL_TEXTURE_2D, texture[1]);
	
	numpolygons = sector1.numpolygons;
	
	//create the world
	// Process Each polygon 
	for (int loop_m = 0; loop_m < numpolygons; loop_m++)
	{
		if (loop_m == 2)
	glBindTexture(GL_TEXTURE_2D, texture[2]);
		if (loop_m == 3)
glBindTexture(GL_TEXTURE_2D, texture[0]);
		glBegin(GL_QUADS);
			glNormal3f( 0.0f, 0.0f, 1.0f);
			x_m = sector1.polygon[loop_m].vertex[0].x;
			y_m = sector1.polygon[loop_m].vertex[0].y;
			z_m = sector1.polygon[loop_m].vertex[0].z;
			u_m = sector1.polygon[loop_m].vertex[0].u;
			v_m = sector1.polygon[loop_m].vertex[0].v;
			glTexCoord2f(u_m,v_m); glVertex3f(x_m,y_m,z_m);
			
			x_m = sector1.polygon[loop_m].vertex[1].x;
			y_m = sector1.polygon[loop_m].vertex[1].y;
			z_m = sector1.polygon[loop_m].vertex[1].z;
			u_m = sector1.polygon[loop_m].vertex[1].u;
			v_m = sector1.polygon[loop_m].vertex[1].v;
			glTexCoord2f(u_m,v_m); glVertex3f(x_m,y_m,z_m);
			
			x_m = sector1.polygon[loop_m].vertex[2].x;
			y_m = sector1.polygon[loop_m].vertex[2].y;
			z_m = sector1.polygon[loop_m].vertex[2].z;
			u_m = sector1.polygon[loop_m].vertex[2].u;
			v_m = sector1.polygon[loop_m].vertex[2].v;
			glTexCoord2f(u_m,v_m); glVertex3f(x_m,y_m,z_m);

			x_m = sector1.polygon[loop_m].vertex[3].x;
			y_m = sector1.polygon[loop_m].vertex[3].y;
			z_m = sector1.polygon[loop_m].vertex[3].z;
			u_m = sector1.polygon[loop_m].vertex[3].u;
			v_m = sector1.polygon[loop_m].vertex[3].v;
			glTexCoord2f(u_m,v_m); glVertex3f(x_m,y_m,z_m);

		glEnd();
	}
//glLoadIdentity();
	for (int index = 0; index < 4; index++)
	{

		if (!painting[index].inventory)
		{
			glPushMatrix();
			
				glTranslatef(painting[index].posx, 0, painting[index].posz);
				glRotatef(time_elapsed/5,0,1.0,0);
		
		
				glBindTexture(GL_TEXTURE_2D, 1);
				glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
				glScaled(.5, .5, .1);
				glCallList(painting[index].id);
			glPopMatrix();
		}
	}
	glDisable(GL_TEXTURE_2D);
///////////////////////////////////////////
//this is the testing ground for the text//
	//glPushMatrix();  //tried to seprate the matrix, but that did nothing
	
	//glTranslatef(0.0f,0.0f,-1.0f); // Move One Unit Into The Screen
	
	glColor3f(1.0f,1.0f,1.0f);
	
	glRasterPos2f(-0.2f, 0.22f);  // Position The Text On The Screen
 	glPrint("Here's some Text!!");
	//glPopMatrix();
////////////////////////////////////////////
	glFlush();
	return TRUE;										// Everything Went OK
}

now, all the 3d drawing goes to plan, but there's no text. Does anyone have any suggestions?? -steve

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I'm not the best to ask but maybe, with what I have to do sometimes , try puting
glprint on top of glColor3f and glRasterPos2f. It might work but I don't know. You might just want to try.

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Your code is almost as messy as mine :D and difficult to follow, but I think the most likely candidate is:

glDisable(GL_TEXTURE_2D);

It's probably unlikely that glEnable() for tex is called from within glprint, hence the text is not drawn.

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If you want the text to be overlayed on the screen - like FPS counters and other stats, then you need to switch from 3D perspective mode to a 2D orthographic project mode before rendering the text. If you intend to have the text in 3D space, then you need to supply x,y, and z coordinates for your text. At the moment you are only providing 2D coordinates (x,y). Using the bitmap font in 3D space is quirky. It will work, but the text will always remain the same height the further away or closer you get, which is not usually what you want. Bitmap fonts are designed to be used in 2D orthographic mode.

eg. For the overlay...


int DrawGLScene(GLvoid) // Here's Where We Do All The Drawing
{

// Switch to 3D perspective mode
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glEnable(GL_DEPTH_TEST);
gluPerspective(45.0f,(double)rcreen_width/(double)screen_height,1.0,100.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

//bool once = false; //used for old movement st
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear The Screen And The Depth Buffer
glLoadIdentity(); // Reset The View

clock_t time_elapsed;
time_elapsed = clock();
GLfloat x_m, y_m, z_m, u_m, v_m;
GLfloat xtrans = -xpos;
GLfloat ztrans = -zpos;
GLfloat ytrans = -headbob-0.4f;
GLfloat sceneroty = 360.0f - yrot;

int numpolygons;
// if (once) //old movement style
// {
//glRotatef(lookupdown,1.0f,0,0);//rotates scene up and down
//glRotatef(sceneroty,0,1.0f,0);//rotates scene right and left


//glTranslatef(xtrans, ytrans, ztrans);//moves the scene to simulate camera movement
// //once = false;
// }


glLoadIdentity();
gluLookAt( -xtrans, -ytrans, -ztrans,
-xtrans-sin(yrot*piover180)*100,-tan(lookupdown*piover180)*100, -ztrans-cos(yrot*piover180)*100,
0.0, 1.0, 0.0);




glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, texture[1]);

numpolygons = sector1.numpolygons;

//create the world
// Process Each polygon
for (int loop_m = 0; loop_m < numpolygons; loop_m++)
{
if (loop_m == 2)
glBindTexture(GL_TEXTURE_2D, texture[2]);
if (loop_m == 3)
glBindTexture(GL_TEXTURE_2D, texture[0]);
glBegin(GL_QUADS);
glNormal3f( 0.0f, 0.0f, 1.0f);
x_m = sector1.polygon[loop_m].vertex[0].x;
y_m = sector1.polygon[loop_m].vertex[0].y;
z_m = sector1.polygon[loop_m].vertex[0].z;
u_m = sector1.polygon[loop_m].vertex[0].u;
v_m = sector1.polygon[loop_m].vertex[0].v;
glTexCoord2f(u_m,v_m); glVertex3f(x_m,y_m,z_m);

x_m = sector1.polygon[loop_m].vertex[1].x;
y_m = sector1.polygon[loop_m].vertex[1].y;
z_m = sector1.polygon[loop_m].vertex[1].z;
u_m = sector1.polygon[loop_m].vertex[1].u;
v_m = sector1.polygon[loop_m].vertex[1].v;
glTexCoord2f(u_m,v_m); glVertex3f(x_m,y_m,z_m);

x_m = sector1.polygon[loop_m].vertex[2].x;
y_m = sector1.polygon[loop_m].vertex[2].y;
z_m = sector1.polygon[loop_m].vertex[2].z;
u_m = sector1.polygon[loop_m].vertex[2].u;
v_m = sector1.polygon[loop_m].vertex[2].v;
glTexCoord2f(u_m,v_m); glVertex3f(x_m,y_m,z_m);

x_m = sector1.polygon[loop_m].vertex[3].x;
y_m = sector1.polygon[loop_m].vertex[3].y;
z_m = sector1.polygon[loop_m].vertex[3].z;
u_m = sector1.polygon[loop_m].vertex[3].u;
v_m = sector1.polygon[loop_m].vertex[3].v;
glTexCoord2f(u_m,v_m); glVertex3f(x_m,y_m,z_m);

glEnd();
}
//glLoadIdentity();
for (int index = 0; index < 4; index++)
{

if (!painting[index].inventory)
{
glPushMatrix();

glTranslatef(painting[index].posx, 0, painting[index].posz);
glRotatef(time_elapsed/5,0,1.0,0);


glBindTexture(GL_TEXTURE_2D, 1);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
glScaled(.5, .5, .1);
glCallList(painting[index].id);
glPopMatrix();
}
}
glDisable(GL_TEXTURE_2D);
///////////////////////////////////////////
//this is the testing ground for the text//

// switch to 2D orthographic mode
// projection matrix mode and reset
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
// Switch to orthographic mode
glOrtho(0.0,(double)screen_width,(double)screen_height,0.0,-1.0,1.0f);
// Back to modelview
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
// No depthtesting or blending (or lighting even)
glDisable(GL_DEPTH_TEST);
glDisable(GL_BLEND);


glPushMatrix(); // this might already be in the glPrint routine.. check it
glTranslatef(0.0f,0.0f,-1.0f); // Move One Unit Into The Screen
glColor3f(1.0f,1.0f,1.0f);
glRasterPos2f(-0.2f, 0.22f); // Position The Text On The Screen
glPrint("Here's some Text!!");
glPopMatrix();

////////////////////////////////////////////
glFlush();
return TRUE; // Everything Went OK
}





(I added a switch 3D section at the top of the routine, and a switch 2D section before the text print part. You will need to change variables/values to work with your program of course).
hth
F451

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allright, got it working. The solution was actually kinda simple. I added this code right before setting the color, raster position and calling the print command:

///////////////////////////////////////////
//this is the testing ground for the text//

glDisable(GL_TEXTURE_2D);
glClear(GL_DEPTH_BUFFER_BIT); // Clear Depth Buffer so text will be on top of everything on the screen
glLoadIdentity(); // Reset The Current Modelview Matrix
glTranslatef(0.0f,0.0f,-1.0f); // Move Text One Unit Into The Screen so it isn't cliped

glColor3f(1.0f,1.0f,1.0f);
// Position The Text On The Screen
glRasterPos2f(-0.2f, 0.22f);
glPrint(message);
////////////////////////////////////////////

glFlush();
return TRUE; // Everything Went OK


thanks for the help, i was thinking in the wrong direction before your sugestions.

-Steve

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      Brain Class
      #include "Brain.h" #include "Sprite.h" #include "Window.h" struct Brain::Implementation { //Just A Flag. bool started; //Window Pointer. Window *window; //Sprite Pointer. Sprite *sprite; }; Brain::Brain(Window *window, Sprite *sprite) { //Create Pointer To Implementation. m_Impl = new Implementation(); //Initialize Implementation. m_Impl->started = true; m_Impl->window = window; m_Impl->sprite = sprite; } Brain::~Brain() { //Delete Pointer To Implementation. delete m_Impl; } void Brain::Start() { } void Brain::Update() { } Window * Brain::GetWindow() { return m_Impl->window; } Sprite * Brain::GetSprite() { return m_Impl->sprite; } bool Brain::GetStart() { return m_Impl->started; } void Brain::SetStart(bool value) { m_Impl->started = value; } Script Class (Its a Brain Subclass!!!)
      #include "Script.h" Script::Script(Window *window, Sprite *sprite) : Brain(window, sprite) { } Script::~Script() { } void Script::Start() { std::cout << "Game Started!" << std::endl; } void Script::Update() { Input *input = this->GetWindow()->GetInput(); Sprite *sp = this->GetSprite(); //Move this sprite. this->GetSprite()->Move(200 * this->GetWindow()->GetDeltaTime(), input->GetKeyDown("left"), input->GetKeyDown("right"), input->GetKeyDown("up"), input->GetKeyDown("down")); std::cout << sp->GetTag().c_str() << ".x = " << sp->GetPos()->x << ", " << sp->GetTag().c_str() << ".y = " << sp->GetPos()->y << std::endl; }  
      Main:
      #include "SpaceShooterEngine.h" #include "Script.h" int main() { Window w("title", 600,600); Scene *scene = new Scene(); Sprite *player = new Sprite("Resources/Images/player.png", "Player", 100,100); Sprite *other = new Sprite("Resources/Images/cherno.png", "Other", 400, 100); Sprite *other2 = new Sprite("Resources/Images/cherno.png", "Other", 300, 400); Brain *brain = new Script(&w, player); player->AddBrain(brain); scene->AddSprite(player); scene->AddSprite(other); scene->AddSprite(other2); w.LoadScene(scene); w.MainLoop(); return 0; }  
       
      I literally can't find what is wrong. If you need more code, ask me to post it. I will also attach all the source files.
      Brain.cpp
      Error.cpp
      IndexBuffer.cpp
      Input.cpp
      Renderer.cpp
      Scene.cpp
      Shader.cpp
      Sprite.cpp
      Texture.cpp
      VertexArray.cpp
      VertexBuffer.cpp
      VertexBufferLayout.cpp
      Window.cpp
      Brain.h
      Error.h
      IndexBuffer.h
      Input.h
      Renderer.h
      Scene.h
      Shader.h
      SpaceShooterEngine.h
      Sprite.h
      Texture.h
      VertexArray.h
      VertexBuffer.h
      VertexBufferLayout.h
      Window.h
    • By Cristian Decu
      Hello fellow programmers,
      For a couple of days now i've decided to build my own planet renderer just to see how floating point precision issues
      can be tackled. As you probably imagine, i've quickly faced FPP issues when trying to render absurdly large planets.
       
      I have used the classical quadtree LOD approach;
      I've generated my grids with 33 vertices, (x: -1 to 1, y: -1 to 1, z = 0).
      Each grid is managed by a TerrainNode class that, depending on the side it represents (top, bottom, left right, front, back),
      creates a special rotation-translation matrix that moves and rotates the grid away from the origin so that when i finally
      normalize all the vertices on my vertex shader i can get a perfect sphere.
      T = glm::translate(glm::dmat4(1.0), glm::dvec3(0.0, 0.0, 1.0)); R = glm::rotate(glm::dmat4(1.0), glm::radians(180.0), glm::dvec3(1.0, 0.0, 0.0)); sides[0] = new TerrainNode(1.0, radius, T * R, glm::dvec2(0.0, 0.0), new TerrainTile(1.0, SIDE_FRONT)); T = glm::translate(glm::dmat4(1.0), glm::dvec3(0.0, 0.0, -1.0)); R = glm::rotate(glm::dmat4(1.0), glm::radians(0.0), glm::dvec3(1.0, 0.0, 0.0)); sides[1] = new TerrainNode(1.0, radius, R * T, glm::dvec2(0.0, 0.0), new TerrainTile(1.0, SIDE_BACK)); // So on and so forth for the rest of the sides As you can see, for the front side grid, i rotate it 180 degrees to make it face the camera and push it towards the eye;
      the back side is handled almost the same way only that i don't need to rotate it but simply push it away from the eye.
      The same technique is applied for the rest of the faces (obviously, with the proper rotations / translations).
      The matrix that result from the multiplication of R and T (in that particular order) is send to my vertex shader as `r_Grid'.
      // spherify vec3 V = normalize((r_Grid * vec4(r_Vertex, 1.0)).xyz); gl_Position = r_ModelViewProjection * vec4(V, 1.0); The `r_ModelViewProjection' matrix is generated on the CPU in this manner.
      // No the most efficient way, but it works. glm::dmat4 Camera::getMatrix() { // Create the view matrix // Roll, Yaw and Pitch are all quaternions. glm::dmat4 View = glm::toMat4(Roll) * glm::toMat4(Pitch) * glm::toMat4(Yaw); // The model matrix is generated by translating in the oposite direction of the camera. glm::dmat4 Model = glm::translate(glm::dmat4(1.0), -Position); // Projection = glm::perspective(fovY, aspect, zNear, zFar); // zNear = 0.1, zFar = 1.0995116e12 return Projection * View * Model; } I managed to get rid of z-fighting by using a technique called Logarithmic Depth Buffer described in this article; it works amazingly well, no z-fighting at all, at least not visible.
      Each frame i'm rendering each node by sending the generated matrices this way.
      // set the r_ModelViewProjection uniform // Sneak in the mRadiusMatrix which is a matrix that contains the radius of my planet. Shader::setUniform(0, Camera::getInstance()->getMatrix() * mRadiusMatrix); // set the r_Grid matrix uniform i created earlier. Shader::setUniform(1, r_Grid); grid->render(); My planet's radius is around 6400000.0 units, absurdly large, but that's what i really want to achieve;
      Everything works well, the node's split and merge as you'd expect, however whenever i get close to the surface
      of the planet the rounding errors start to kick in giving me that lovely stairs effect.
      I've read that if i could render each grid relative to the camera i could get better precision on the surface, effectively
      getting rid of those rounding errors.
       
      My question is how can i achieve this relative to camera rendering in my scenario here?
      I know that i have to do most of the work on the CPU with double, and that's exactly what i'm doing.
      I only use double on the CPU side where i also do most of the matrix multiplications.
      As you can see from my vertex shader i only do the usual r_ModelViewProjection * (some vertex coords).
       
      Thank you for your suggestions!
       
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