Re: [PyOpenGL-Users] Drawing a bitmap at "native" resolution
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Re: [PyOpenGL-Users] Drawing a bitmap at "native" resolution
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From: Christopher B. <Chr...@no...> - 2011-05-03 15:05:35
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On 5/3/11 12:18 AM, Nicolas Rougier wrote:
>
>
> Here is a quick example:
Very nice, thanks!
It's going to take me a bit to digest that, but it looks like all the
key pieces are there that I need.
And it worked out of the box for me.
again, thanks!
-Chris
>
>
> 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... <mailto: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
>> ------------------------------------------------------------------------------
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>
--
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