Displaying a simple 2D textured rectangle inside a wxGLCanvas using PyOpenGL

opengl, pyopengl, python, textures, wxpython

Solution

Well, the critical mistake I was making was not scaling the float values of my input data to between 0 and 1 - all my pixels were >1 so the quad rendered as white! I had a bit of trouble finding good examples of how to use `wxGLCanvas`es, so here's a simple texture rendered in a `wxGLCanvas` for anyone who might find it useful.

import numpy as np
from scipy.misc import ascent
import OpenGL.GL as gl
import wx
from wx.glcanvas import GLCanvas


class Canvas(GLCanvas):

    def __init__(self, parent):
        """create the canvas """
        super(Canvas, self).__init__(parent)
        self.texture = None

        # execute self.onPaint whenever the parent frame is repainted
        wx.EVT_PAINT(self, self.onPaint)

    def initTexture(self):
        """init the texture - this has to happen after an OpenGL context
        has been created
        """

        # make the OpenGL context associated with this canvas the current one
        self.SetCurrent()

        data = np.uint8(np.flipud(ascent()))
        w, h = data.shape

        # generate a texture id, make it current
        self.texture = gl.glGenTextures(1)
        gl.glBindTexture(gl.GL_TEXTURE_2D, self.texture)

        # texture mode and parameters controlling wrapping and scaling
        gl.glTexEnvf(gl.GL_TEXTURE_ENV, gl.GL_TEXTURE_ENV_MODE, gl.GL_MODULATE)
        gl.glTexParameterf(
            gl.GL_TEXTURE_2D, gl.GL_TEXTURE_WRAP_S, gl.GL_REPEAT)
        gl.glTexParameterf(
            gl.GL_TEXTURE_2D, gl.GL_TEXTURE_WRAP_T, gl.GL_REPEAT)
        gl.glTexParameterf(
            gl.GL_TEXTURE_2D, gl.GL_TEXTURE_MAG_FILTER, gl.GL_LINEAR)
        gl.glTexParameterf(
            gl.GL_TEXTURE_2D, gl.GL_TEXTURE_MIN_FILTER, gl.GL_LINEAR)

        # map the image data to the texture. note that if the input
        # type is GL_FLOAT, the values must be in the range [0..1]
        gl.glTexImage2D(gl.GL_TEXTURE_2D, 0, gl.GL_RGB, w, h, 0,
                        gl.GL_LUMINANCE, gl.GL_UNSIGNED_BYTE, data)

    def onPaint(self, event):
        """called when window is repainted """
        # make sure we have a texture to draw
        if not self.texture:
            self.initTexture()
        self.onDraw()

    def onDraw(self):
        """draw function """

        # make the OpenGL context associated with this canvas the current one
        self.SetCurrent()

        # set the viewport and projection
        w, h = self.GetSize()
        gl.glViewport(0, 0, w, h)

        gl.glMatrixMode(gl.GL_PROJECTION)
        gl.glLoadIdentity()
        gl.glOrtho(0, 1, 0, 1, 0, 1)

        gl.glMatrixMode(gl.GL_MODELVIEW)
        gl.glLoadIdentity()
        gl.glClear(gl.GL_COLOR_BUFFER_BIT)

        # enable textures, bind to our texture
        gl.glEnable(gl.GL_TEXTURE_2D)
        gl.glBindTexture(gl.GL_TEXTURE_2D, self.texture)
        gl.glColor3f(1, 1, 1)

        # draw a quad
        gl.glBegin(gl.GL_QUADS)
        gl.glTexCoord2f(0, 1)
        gl.glVertex2f(0, 1)
        gl.glTexCoord2f(0, 0)
        gl.glVertex2f(0, 0)
        gl.glTexCoord2f(1, 0)
        gl.glVertex2f(1, 0)
        gl.glTexCoord2f(1, 1)
        gl.glVertex2f(1, 1)
        gl.glEnd()

        gl.glDisable(gl.GL_TEXTURE_2D)

        # swap the front and back buffers so that the texture is visible
        self.SwapBuffers()


def run():
    app = wx.App()
    fr = wx.Frame(None, size=(512, 512), title='wxPython texture demo')
    canv = Canvas(fr)
    fr.Show()
    app.MainLoop()

if __name__ == "__main__":
    run()

Problem

Original source