pyopengl-users

[PyOpenGL-Users] First fragment shader - corrected

[Mads I. <mp...@co...>]

Please ignore the first post which had errors. This one is correct

OK, so its time to write the first most simple fragment shader ever. But
it doesn't work:

void main()
{
        gl_FragColor = vec4(0.5, 0.5, 0.5, 1.0);
}

No teapot - just black. Changing to

gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);

gives red teapot, and vec4(0.0, 1.0, 0.0, 1.0) and vec4(0.0, 0.0, 1.0, 
1.0) gives green and blue teapot. But any RGB triplet with values < 1.0 
are always truncated to 0.0. For example:


vec4(1.0, 0.5, 0.0, 1.0) -> pure red
vec4(0.0, 0.5, 0.5, 1.0) -> pure black

I have no clue about whats up.

Best regards,

Mads

-- 
+-------------------------------------------------------------+
| Mads Ipsen, Scientific developer                            |
+-------------------------------+-----------------------------+
| QuantumWise A/S               | phone:         +45-29716388 |
| Nørre Søgade 27A              | www:    www.quantumwise.com |
| DK-1370 Copenhagen K, Denmark | email:  mp...@qu... |
+-------------------------------+-----------------------------+

Re: [PyOpenGL-Users] First fragment shader - corrected

[Mads I. <mp...@co...>]

No, I haven't solved this one yet. Here's what I found out:

1. Works in a pure PyOpenGL setting on Ubuntu 8.04 with an ATI card 
(fglrx).
2. *Fails* in a QGLWidget on Ubuntu 8.04 with an ATI card (fglrx).
3. Works in a pure PyOpenGL setting on Ubuntu 9.04 with an NVidia card.
4. Works in a QGLWidget Ubuntu 8.04 with an ATI card.

It's really strange! Anyway I have attached my PyOpenGL version below. 
If you think I am doing something that potentially could mess things up, 
please let me know.


from OpenGL.GL import *
from OpenGL.GLU import *
from OpenGL.GLUT import *

theta = 0.0

def InitGL(Width, Height):                glClearColor(1.0, 1.0, 1.0, 
1.0)      glEnable(GL_DEPTH_TEST)               
glShadeModel(GL_SMOOTH)                 glMatrixMode(GL_PROJECTION)
   glLoadIdentity()                   
                                         gluPerspective(45.0, 
float(Width)/float(Height), 0.1, 100.0)

   glMatrixMode(GL_MODELVIEW)

   setShaders()

def ReSizeGLScene(w, h):
   ratio = 1.0 * w / h

   glMatrixMode(GL_PROJECTION)
   glLoadIdentity()
         glViewport(0, 0, w, h);

   gluPerspective(45,ratio,1,1000)
   glMatrixMode(GL_MODELVIEW);

def DrawGLScene():
   global theta
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
   glLoadIdentity()

   gluLookAt(0.0, 0.0, 5.0,
             0.0, 0.0,-1.0,
             0.0, 1.0, 0.0)

   glRotatef(theta, 0, 1, 1);
   glColor(0.0, 0.5, 0.5, 1.0)
   glutSolidTeapot(1)

   glutSwapBuffers()

   theta += 0.1

def setShaders():
   v = glCreateShader(GL_VERTEX_SHADER)
   f = glCreateShader(GL_FRAGMENT_SHADER)

   vs = ['''void main()
   {          gl_Position = ftransform();
   }''']

   fs = ['''void main()
   {
       gl_FragColor = vec4(1.0, 0.5, 0.5, 1.0);
   }''']
     glShaderSource(v, vs)
   glShaderSource(f, fs)
     glCompileShader(v)
   glCompileShader(f)
     p = glCreateProgram()
   glAttachShader(p,v)
   glAttachShader(p,f)
     glLinkProgram(p)
   glUseProgram(p)

def keyPressed(*args):
   if args[0] == '\x1b':
       sys.exit()

def main():
   glutInit(sys.argv)

   glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH)
   glutInitWindowSize(640, 480)
   glutInitWindowPosition(0, 0)
   glutCreateWindow("Shader")
   glutDisplayFunc(DrawGLScene)
   glutIdleFunc(DrawGLScene)
   glutReshapeFunc(ReSizeGLScene)
   glutKeyboardFunc(keyPressed)
   InitGL(640, 480)
   glutMainLoop()

# Print message to console, and kick off the main to get it rolling.

if __name__ == "__main__":
   print "Hit ESC key to quit."
   main()

Ben De Luca wrote:
> Did you figure it out? your shader looks to be ok, which implies the 
> issue is out side of your shader some where?
>
>
> What platform are you on?
>
>
> On 12/10/2009, at 8:56 AM, Mads Ipsen wrote:
>
>> Please ignore the first post which had errors. This one is correct
>>
>> OK, so its time to write the first most simple fragment shader ever. But
>> it doesn't work:
>>
>> void main()
>> {
>>        gl_FragColor = vec4(0.5, 0.5, 0.5, 1.0);
>> }
>>
>> No teapot - just black. Changing to
>>
>> gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
>>
>> gives red teapot, and vec4(0.0, 1.0, 0.0, 1.0) and vec4(0.0, 0.0, 1.0,
>> 1.0) gives green and blue teapot. But any RGB triplet with values < 1.0
>> are always truncated to 0.0. For example:
>>
>>
>> vec4(1.0, 0.5, 0.0, 1.0) -> pure red
>> vec4(0.0, 0.5, 0.5, 1.0) -> pure black
>>
>> I have no clue about whats up.
>>
>> Best regards,
>>
>> Mads
>>
>> -- 
>> +-------------------------------------------------------------+
>> | Mads Ipsen, Scientific developer                            |
>> +-------------------------------+-----------------------------+
>> | QuantumWise A/S               | phone:         +45-29716388 |
>> | Nørre Søgade 27A              | www:    www.quantumwise.com |
>> | DK-1370 Copenhagen K, Denmark | email:  mp...@qu... |
>> +-------------------------------+-----------------------------+
>>
>>
>>
>> ------------------------------------------------------------------------------ 
>>
>> Come build with us! The BlackBerry(R) Developer Conference in SF, CA
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>> ahead of the curve. Join us from November 9 - 12, 2009. Register now!
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>


-- 
+-------------------------------------------------------------+
| Mads Ipsen, Scientific developer                            |
+-------------------------------+-----------------------------+
| QuantumWise A/S               | phone:         +45-29716388 |
| Nørre Søgade 27A              | www:    www.quantumwise.com |
| DK-1370 Copenhagen K, Denmark | email:  mp...@qu... |
+-------------------------------+-----------------------------+

Re: [PyOpenGL-Users] First fragment shader - corrected

[Mads I. <mp...@co...>]

I keep adding typos. Here's what it should be (sorry):

1. Works in a pure PyOpenGL setting on Ubuntu 8.04 with an ATI card
(fglrx).
2. *Fails* in a QGLWidget on Ubuntu 8.04 with an ATI card (fglrx).
3. Works in a pure PyOpenGL setting on Ubuntu 9.04 with an NVidia card.
4. Works in a QGLWidget Ubuntu 9.04 with an NVidia card.

-- 
+-------------------------------------------------------------+
| Mads Ipsen, Scientific developer                            |
+-------------------------------+-----------------------------+
| QuantumWise A/S               | phone:         +45-29716388 |
| Nørre Søgade 27A              | www:    www.quantumwise.com |
| DK-1370 Copenhagen K, Denmark | email:  mp...@qu... |
+-------------------------------+-----------------------------+