Im using PyOpenGL with PyQt5 widgets. In my OpenGL widget I have the following code:
class Renderizador(QOpenGLWidget):
def __init__(self, parent=None):
super().__init__(parent)
self._x = -0.1
self._y = -0.1
self._z = -0.1
self._rx = 45
self._ry = 45
self._rz = -45
self.vertices_vertical = [[100, 100, 0], [100, -100, 0],
[-100, -100, 0], [-100, 100, 0]]
self.vertices_horizontal = [[100, 0, -100], [100, 0, 100],
[-100, 0, 100], [-100, 0, -100]]
def initializeGL(self):
glClear(GL_COLOR_BUFFER_BIT)
glEnable(GL_DEPTH_TEST)
glMatrixMode(GL_PROJECTION)
glLoadIdentity()
glOrtho(-1, 1, 1, -1, -15, 1)
glTranslate(self._x, self._y, self._z)
glRotate(self._rx, 1, 0, 0)
glRotate(self._ry, 0, 1, 0)
glRotate(self._rz, 0, 0, 0)
def paintGL(self):
glClearColor(1, 1, 1, 1)
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
glMatrixMode(GL_MODELVIEW)
glLoadIdentity()
glTranslate(self._x, self._y, self._z)
glRotate(self._rx, 1, 0, 0)
glRotate(self._ry, 0, 1, 0)
glRotate(self._rz, 0, 0, 1)
# Axis lines
glBegin(GL_LINES)
glColor3d(1, 0, 0)
glVertex3d(0, 0, 0)
glVertex3d(1, 0, 0)
glColor3d(0, 1, 0)
glVertex3d(0, 0, 0)
glVertex3d(0, 1, 0)
glColor3d(0, 0, 1)
glVertex3d(0, 0, 0)
glVertex3d(0, 0, 1)
glEnd()
# Plane drawing, does not work
glEnable(GL_BLEND)
glBlendFunc(GL_SRC_ALPHA, GL_DST_COLOR)
glBegin(GL_QUADS)
glColor4fv((0, 1, 0, 0.6))
for vertex in range(4):
glVertex3fv(self.vertices_vertical[vertex])
glColor4fv((1, 0, 0, 0.6))
for vertex in range(4):
glVertex3fv(self.vertices_horizontal[vertex])
glEnd()
glDisable(GL_BLEND)
Why the two planes are not rendered? I changed the background color to white, using the glClearColor and then a glClear functions before of doing that It worked. I can see the axis lines, but not the planes I draw.
You can`t "see" the planes because of the Blending.
The blend function (see glBlendFunc)
glBlendFunc(GL_SRC_ALPHA, GL_DST_COLOR)
meas the following (R red, G green, B blue, A alphas, s source, d destintion) :
R = Rs * As + Rd * Rd
G = Gs * As + Gd * Gd
B = Bs * As + Bd * Bd
A = As * As + Ad * Ad
In your case the alpha channel of the source is 0.6 and the destination color is the color which was used to clear the framebuffer (1, 1, 1, 1):
R = Rs * 0.6 + 1 * 1
G = Gs * 0.6 + 1 * 1
B = Bs * 0.6 + 1 * 1
A = As * 0.6 + 1 * 1
So the result color is white in any case, because the result for each color channel is grater than 1.