Thanks for that.
The thing is that I'm trying to do that in python and I'm stuck at
modelview[16] in python because it is in [4][4] array in python and I'm
not sure which one is rows and cols from c++ to python.
Also, when I draw the quad at the object's center, do I need to do a
glTranslatef? I'm guessing I do, right?
Thanks again.
Astan
Forrest Voight wrote:
I meant after the modelview matrix was tranformed to the camera position.
This is the only code you need for billboarding - transforming the
matrix to make the object always face the camera:
float modelview[16];
int i,j;
// save the current modelview matrix
glPushMatrix();
// get the current modelview matrix
glGetFloatv(GL_MODELVIEW_MATRIX , modelview);
// undo all rotations
// beware all scaling is lost as well
for( i=0; i<3; i++ )
for( j=0; j<3; j++ ) {
if ( i==j )
modelview[i*4+j] = 1.0;
else
modelview[i*4+j] = 0.0;
}
// set the modelview with no rotations and scaling
glLoadMatrixf(modelview);
drawObject();
// restores the modelview matrix
glPopMatrix();
drawObject would be replaced by the code that draws a quad at the
object's center. You would need to store the aspect ratio of the
output of font.render (aspect = width/height) and use it to draw a
correctly sized quad - for example, with a height of 1 and a width of
aspect. The quad would need the appropriate texcoords - just 0,0 0,1
1,1 and 1,0 for the corners of the texture with the rendered text.
On Thu, Jul 2, 2009 at 10:41 PM, Astan Chee<astan.chee@xxxxxxxxx> wrote:
What do you mean "after the matrices are set"? is it when I'm doing an
"initgl" like this:
glShadeModel(GL_SMOOTH)
glClearColor(0.0, 0.0, 0.0, 0.0)
glClearDepth(1.0)
glEnable(GL_DEPTH_TEST)
glDepthFunc(GL_LEQUAL)
glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST)
glEnable(GL_COLOR_MATERIAL)
glEnable(GL_TEXTURE_2D)
or when the window resize is being called:
def resize(self,(width, height)):
if height==0:
height=1
glViewport(0, 0, width, height)
glMatrixMode(GL_PROJECTION)
glLoadIdentity()
gluPerspective(45, 1.0*width/height, 1.0, 10000.0)
glMatrixMode(GL_MODELVIEW)
glLoadIdentity()
also, you lost me at your last sentence...I have no idea what that means but
I'll google around.
thanks again
Forrest Voight wrote:
When are you doing the gluProject? It should be after the matrices are
set for the frame. Can you paste the code for that?
To billboard text, you'd render it to a texture.
Something like:
surface = self.font.render(s, True, (255, 255, 255))
gluBuild2DMipmaps(GL_TEXTURE_2D, GL_RGBA, surface.get_width(),
surface.get_height(), GL_RGBA, GL_UNSIGNED_BYTE,
pygame.image.tostring(surface, "RGBA", True)
Then, when rendering, transform the modelview matrix as in that link,
and draw a quad with the correct aspect ratio.
On Wed, Jul 1, 2009 at 10:58 PM, Astan Chee<astan.chee@xxxxxxxxx> wrote:
Thanks for that, but it doesn't seem to work. Well, it gives coordinates of
x,y(,z) but when the camera changes angle (but not position), the
coordinates don't change. What else do I need to be doing in this?
Anyway, I also forgot to mention this is how I make the text images:
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)
Since I make the text this way, I'm thinking of just doing it billboard but
I'm not sure how to implement half of this.
Thanks again for any help.
Cheers
Astan
Ian Mallett wrote:
Er, the last three arguments return the data in C. In Python, the syntax is
different:
C: gluProject(objx,objy,objz,model,proj,view,winx,winy,winz)
Python: winx,winy,winz = gluProject(objx,objy,objz,model,proj)
And yes, it returns a z-coord, which should take into account the near
clipping plane. As long as the plane is ~0, (x,y) should be fairly
accurate.
Keep in mind that the (x,y) coordinates are *real* coordinates, (i.e., the y
is not flipped). (0,0) is the bottom left. If you rasterize the font as
you were, it shouldn't be a problem.
Ian
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