Re: [PyOpenGL-Users] Drawing a bitmap at "native" resolution

[Nicolas R. <Nic...@in...>]

Here is a quick example:



import sys
import OpenGL.GL as gl
import OpenGL.GLU as glu
import OpenGL.GLUT as glut


def on_display():
    global theta, phi

    gl.glClear(gl.GL_COLOR_BUFFER_BIT | gl.GL_DEPTH_BUFFER_BIT)
    gl.glColor(0,0,0,1)

    # Push rotation matrix onto stack
    gl.glPushMatrix()
    gl.glRotatef(theta, 0,0,1)
    gl.glRotatef(phi, 0,1,0)

    # Transform coordinates from 3d space to window 2d
    modelview = gl.glGetDoublev(gl.GL_MODELVIEW_MATRIX)
    projection= gl.glGetDoublev(gl.GL_PROJECTION_MATRIX)
    viewport  = gl.glGetIntegerv(gl.GL_VIEWPORT)
    coords  = [ ( 1,  1,  1), ( 1,  1, -1),
                ( 1, -1,  1), (-1,  1,  1),
                ( 1, -1, -1), (-1, -1,  1),
                (-1,  1, -1), (-1, -1, -1) ]
    pcoords = []
    for x,y,z in coords:
        pcoords.append(glu.gluProject(x,y,z, modelview, projection, viewport))

    # Draw cube
    glut.glutWireCube(2)

    # Pop out rotation matrix
    gl.glPopMatrix()

    # Setup an orthogonal projection
    gl.glMatrixMode(gl.GL_PROJECTION)
    gl.glPushMatrix()
    gl.glLoadIdentity()
    gl.glOrtho(0, viewport[2], 0, viewport[3], -1, 1)
    gl.glMatrixMode(gl.GL_MODELVIEW)
    gl.glPushMatrix()
    gl.glLoadIdentity()
    for x,y,z in pcoords:
        gl.glBegin(gl.GL_LINE_LOOP)
        gl.glVertex(x-20,y-5,0), gl.glVertex(x-20,y+5,0)
        gl.glVertex(x+20,y+5,0), gl.glVertex(x+20,y-5,0)
        gl.glEnd()
    gl.glMatrixMode(gl.GL_PROJECTION)
    gl.glPopMatrix()
    gl.glMatrixMode(gl.GL_MODELVIEW)
    gl.glPopMatrix()
    glut.glutSwapBuffers()


def on_reshape(width, height):
    gl.glViewport(0, 0, width, height)
    gl.glMatrixMode( gl.GL_PROJECTION )
    gl.glLoadIdentity( )
    glu.gluPerspective( 45.0, float(width)/float(height), 2.0, 10.0 )
    gl.glMatrixMode( gl.GL_MODELVIEW )
    gl.glLoadIdentity( )
    gl.glTranslatef( 0.0, 0.0, -5.0 )


def on_keyboard(key, x, y):
    if key == '\033':
        sys.exit()

def on_timer(value):
    global theta, phi
    theta += 0.25
    phi += 0.25
    glut.glutPostRedisplay()
    glut.glutTimerFunc(10, on_timer, 0)


if __name__ == '__main__':
    glut.glutInit(sys.argv)
    glut.glutInitDisplayMode(glut.GLUT_DOUBLE | glut.GLUT_RGB | glut.GLUT_DEPTH)
    glut.glutCreateWindow("Python billboard")
    glut.glutReshapeWindow(400, 400)
    glut.glutDisplayFunc(on_display)
    glut.glutReshapeFunc(on_reshape)
    glut.glutKeyboardFunc(on_keyboard)
    glut.glutTimerFunc(10, on_timer, 0)
    gl.glClearColor(1,1,1,1);
    theta, phi = 0, 0
    glut.glutMainLoop()


Nicolas




On May 3, 2011, at 7:31 AM, Ian Mallett wrote:

> On Mon, May 2, 2011 at 3:18 PM, Christopher Barker <Chr...@no...> wrote:
> Hi folks,
> 
> Anyone know of a performant way to draw a bitmap at its "native"
> resolution -- i.e. one pixel in the bitmap is one pixel on screen,
> regardless of zoom level, etc. I think I've heard this referred to as
> "billboard" view, but that may be a term specific to one visualization
> lib (VTK, maybe)?
> 
> Anyway, the task at hand is using bitmaps fonts as textures to do simple
> text labels, lot of them, in a scientific visualization app.
> 
> For each data point ( up to 100s of thousands ) we need a little text
> label. But we want the text to not change size as the user zooms in or out.
> There's not a way to get around projecting the labels' locations on screen.  You'd have to use gluProject(...).  If you want to be fancy, you can use a vertex shader to project to get each coordinate.
> 
> From there, set up a 2D view.  Then, draw each label at the screen coordinate of its projected location, using textured quads the same size as your textures.
> 
> Ian
> ------------------------------------------------------------------------------
> WhatsUp Gold - Download Free Network Management Software
> The most intuitive, comprehensive, and cost-effective network 
> management toolset available today.  Delivers lowest initial 
> acquisition cost and overall TCO of any competing solution.
> http://p.sf.net/sfu/whatsupgold-sd_______________________________________________
> PyOpenGL Homepage
> http://pyopengl.sourceforge.net
> _______________________________________________
> PyOpenGL-Users mailing list
> PyO...@li...
> https://lists.sourceforge.net/lists/listinfo/pyopengl-users