[pygame] Positioning Objects in 3D w/ Pygame/OpenGL

[Kris Schnee <kschnee@xxxxxxxxxx>]

I've built a demo of a rotating, tilted 3D landscape using Pygame and 
OpenGL (http://www.xepher.net/~kschnee/landscape2.jpg), after reading 
the great NeHe tutorials and their Python translations.

I've got a bunch of cubes that seem to spin around a distant Y-axis, as 
in games like "Final Fantasy Tactics." But I don't know how to draw 2D 
sprites on that landscape, eg. a character standing on the blocks. I 
could put a rectangle in the right spot and texture it with a character 
image, but how can I rotate it so that it's facing the screen?

The blocks get positioned by moving back from the screen, then rotating, 
then getting drawn relative to the Y-axis. Following the same logic to 
draw a sprite would rotate the rectangle, which I don't want.

I'm using a homemade Camera class to define the view. (You're free to 
copy the code if you like it.) Any ideas?

Kris


class Camera:
    def __init__(self, location=[-0.0,2.0,16.0], rotation=0.0, tilt=45):
        """Modifies OpenGL views to simulate a controllable camera view."""
        self.location = None
        self.Locate(location,True)
        self.rotation = rotation
        self.tilt = tilt
        self.spinning = 0 ## When this is nonzero, I spin on HandleSpin().
        self.spinrate = 5
    def Rotate(self,angle,absolute=False):
        """Instantly rotate."""
        if absolute:
            self.rotation = angle
        else:
            self.rotation += angle
    def SetSpin(self,angle=0):
        """Indicate that I should start rotating."""
        self.spinning = angle
    def HandleSpin(self):
        """Rotate over time if SetSpin has been called."""
        if self.spinning:
            if self.spinning > 0:
                self.Rotate(self.spinrate)
                self.spinning -= self.spinrate
            else:
                self.Rotate(-self.spinrate)
                self.spinning += self.spinrate
            ## If there's a leftover, apply it.
            if abs(self.spinning) < self.spinrate:
                self.Rotate(self.spinning)
                self.spinning = 0
    def Locate(self,location,absolute=False):
        """Set/Change my location."""
        if absolute:
            self.location = [ -location[0],-location[1],-location[2] ]
        else:
            self.location = [ 
self.location[0]-location[0],self.location[1]-location[1],self.location[2]-location[2] 
]
    def Tilt(self,angle,absolute=False):
        if absolute:
            self.tilt = angle
        else:
            self.tilt += angle
    def ApplyLocation(self):
        glTranslatef(self.location[0],self.location[1],self.location[2])
    def ApplyRotation(self):
        glRotatef(self.rotation,0,1,0)
    def ApplyTilt(self):
        glRotatef(self.tilt,1,0,0)
    def Apply(self):
        """Call this before drawing each object."""
        self.ApplyLocation()
        self.ApplyTilt()
        self.ApplyRotation()
    def ApplyForSprite(self):
        """Experimental; not working yet."""
        self.ApplyLocation()
        self.ApplyTilt()