Re: [PyOpenGL-Users] converting "object position" to "view position" in (py)opengl

[Astan C. <ast...@al...>]

Hi,
I'm drawing characters using pygame and pyopengl like this:
def __init__(self):
        pygame.font.init()
        self.font = pygame.font.Font(FONT,18)
        self.char = []
        for c in range(256):
            self.char.append(self.CreateCharacter(chr(c)))
        self.char = tuple(self.char)
    def CreateCharacter(self,s):
        try:
            letter_render = self.font.render(s,1,(255,255,255), (0,0,0))
            letter = pygame.image.tostring(letter_render,'RGBA',1)
            letter_w,letter_h = letter_render.get_size()
        except:
            letter = None
            letter_w = letter_h= 0
        return (letter,letter_w,letter_h)
   
    def textView(self):
        w = self.Screen[0]
        h = self.Screen[1]
        glViewport(0,0,w,h)
        glMatrixMode(GL_PROJECTION)
        glLoadIdentity()
        glOrtho(0.0, w - 1.0, 0.0, h - 1.0, -1.0, 1.0)
        glMatrixMode(GL_MODELVIEW)
        glLoadIdentity()

    def Print(self,s,x,y):
        s = str(s)
        i = 0
        lx = 0
        length = len(s)
        self.textView()
        glPushMatrix()
        while i < length:
            glRasterPos2i(x + lx, y)
            ch = self.char[ ord( s[i] ) ]
            glDrawPixels(ch[1], ch[2], GL_RGBA, GL_UNSIGNED_BYTE, ch[0])
            lx += ch[1]
            i += 1
        glPopMatrix() 
and then when I need to print in a certain part of the screen, I do a 
self.Print("text",0,0) which will do a print on the bottom left corner.
I don't think i'm using glBitmap
Cheers
Astan

Dirk Reiners wrote:
> 	Hi Astan,
>
> Astan Chee wrote:
>   
>> Hi,
>> Im relatively new to opengl and I'm not familiat with its jargon but 
>> what I have is objects in a 3D world in various positions and a camera 
>> that can "move" around. What I'm trying to do is if the distance between 
>> object and camera is close enough, display some information on the 
>> screen on the object.
>> I know how to calculate distance and I know how to print/display text in 
>> opengl (I'm using glOrtho and glRasterPos2i to map out the characters 
>> one at a time).
>> Anyway, what I'm having problems with is how do I calculate where to 
>> display these information on the screen so that it overlaps the object 
>> (assuming I know the distance and the angle of the camera and the object 
>> relative to the camera). Does this make sense? I've attached an image 
>> that I photoshopped to look like what I'm trying to do.
>>     
>
> What are you using to draw the characters? glBitmap? Your use of glRasterPos2i 
> hints at that.
>
> In that case you can just ignore the glOrtho and use glRasterPos3f to position 
> your text in the 3D scene (e.g. in the center of the object). The main 
> difficulty is putting the chacaters next to each other, and glBitmap takes care 
> of that nicely.
>
> If you're using a different method things get a little more complicated (but not 
> too much, really).
>
> 	Dirk
>
>