Gremlin Development Notes

Gremlin is a backplot application that may be used with user interfaces.

For now, this will be a place for notes on particular issues with Gremlin. Hopefully, it will become a comprehensive reference that may be used to create a formal entry into the manual.

Adding Rear Tool Lathe Features

Some features are needed for the development of a user interface for a lathe using a tool post or changer located behind the spindle. Primarily, the X axis direction has been changed so that the X plus direction points away from the normal operator position. The issues that come from this are:

1.1. How best to flag this configuration so that software applies the proper actions?

The solution so far is to check the .ini file GEOMETRY tag for "-XY". The the code path parallels the code for LATHE=1:

gremlin.py

...
class Gremlin(gtk.gtkgl.widget.DrawingArea, glnav.GlNavBase,
              rs274.glcanon.GlCanonDraw):
...
        temp = inifile.find("DISPLAY", "LATHE")
        self.lathe_option = bool(temp == "1" or temp == "True" or temp == "true" )
        temp2 = inifile.find("DISPLAY", "GEOMETRY")
        self.is_rear_tp_lathe = bool(temp2 == "-XZ")
...
    def is_lathe(self): return self.lathe_option
    def is_rear_tool_post_lathe(self): return self.is_rear_tp_lathe

glcanon.py

...
class GLCanon(Translated, ArcsToSegmentsMixin):
...
    def draw_axes(self, n, letters="XYZ"):
...
            if self.is_lathe():
...
    def calc_extents(self):

        self.min_extents, self.max_extents, self.min_extents_notool, self.max_extents_notool = gcode.calc_extents(self.arcfeed, self.feed, self.traverse)
        if self.is_rear_tp_lathe:
            # the min/max come in from gcode_calc extents as the negative of the actual value
            # if we're displaying a plot for a rear TP lathe
            self.min_extents[0] *= (-1)
            self.max_extents[0] *= (-1)   
...
    def draw_axes(self, n, letters="XYZ"):
        glNewList(n, GL_COMPILE)
        x,y,z,p = 0,1,2,3
        s = self.stat
        view = self.get_view()


        glColor3f(*self.colors['axis_x'])
        glBegin(GL_LINES)
        if self.is_rear_tool_post_lathe():
            glVertex3f(-1.0,0.0,0.0)
        else:
            glVertex3f(1.0,0.0,0.0)
        glVertex3f(0.0,0.0,0.0)
        glEnd()

        if view != x:
            glPushMatrix()
            if self.is_lathe():
                if self.is_rear_tool_post_lathe():
                    glTranslatef(-1.3, 0, 0)
                    glRotatef(-90, 0, 0, 1)
                    glRotatef(90, 0, 1, 0)
                else:
                    glTranslatef(1.3, -0.1, 0)
                    glTranslatef(0, 0, -0.1)
                    glRotatef(-90, 0, 1, 0)
                    glRotatef(90, 1, 0, 0)
                    glTranslatef(0.1, 0, 0)
...

1.2. The Gremlin X axis origin arrow needs to point up instead of down

glcanon.py

...
        glColor3f(*self.colors['axis_x'])
        glBegin(GL_LINES)
        if self.is_rear_tool_post_lathe():
            glVertex3f(-1.0,0.0,0.0)  # Draws line up
        else:
            glVertex3f(1.0,0.0,0.0)  # Draws line down
        glVertex3f(0.0,0.0,0.0)
        glEnd()

        if view != x:
            glPushMatrix()
            if self.is_lathe():
                if self.is_rear_tool_post_lathe():
                    glTranslatef(-1.3, 0, 0)  # Draws an X above the line
                    glRotatef(-90, 0, 0, 1)
                    glRotatef(90, 0, 1, 0)  # Rotates it to face the viewer
                else:
                    glTranslatef(1.3, -0.1, 0)
                    glTranslatef(0, 0, -0.1)
                    glRotatef(-90, 0, 1, 0)
                    glRotatef(90, 1, 0, 0)
                    glTranslatef(0.1, 0, 0)
...

1.3. The tool tip image is on the wrong side of the tool's control point

glcanon.py

Study of how tool orientation 9 is drawn

... if orientation == 9: glBegin(GL_TRIANGLE_FAN) for i in range(37): # 10 degree increments in 360 t = i * math.pi / 18 # angle in Radians glVertex3f(radius * math.cos(t), 0.0, radius * math.sin(t)) glEnd() ...
This image shows a circle using the same GL_TRIANGLE_FAN method except at 30 degree increments.

This sheds light on the other tool orientations which prompts a proper fix.
The fix was easier than I thought. I copied the existing orientation map and swapped settings for 2 and 3, 6 and 8, and 1 and 4. Easy peasy.

glcanon.py

...
    def lathetool(self, current_tool):

        if self.is_rear_tool_post_lathe:
            lathe_shapes = [
                None,                           # 0
                (-1,-1), (-1,1), (1,1), (1,-1), # 1..4
                (0,-1), (-1,0), (0,1), (1,0),   # 5..8
                (0,0)                           # 9
            ]
        else:
            lathe_shapes = [
                None,                           # 0
                (1,-1), (1,1), (-1,1), (-1,-1), # 1..4
                (0,-1), (1,0), (0,1), (-1,0),   # 5..8
                (0,0)                           # 9
            ]
...
        if orientation == 9:
            glBegin(GL_TRIANGLE_FAN)
            for i in range(37):  # 10 degree increments in 360
                t = i * math.pi / 18  # angle in Radians
                glVertex3f(radius * math.cos(t), 0.0, radius * math.sin(t))
            glEnd()
        else:
#            dx, dy = self.lathe_shapes[orientation]
            dx, dy = lathe_shapes[orientation]
            min_angle = min(backangle, frontangle) * math.pi / 180
            max_angle = max(backangle, frontangle) * math.pi / 180
...

1.4. The soft limit and grid borders are reversed on the X axis

fix for limits

glcanon.py

...
    def redraw(self):
        s = self.stat
        s.poll()

        machine_limit_min, machine_limit_max = self.soft_limits()
...
        if self.get_show_limits():
            glLineWidth(1)
            glColor3f(1.0,0.0,0.0)
            glLineStipple(1, 0x1111)
            glEnable(GL_LINE_STIPPLE)
            glBegin(GL_LINES)

            if self.is_rear_tool_post_lathe():
                x_dir = -1
            else:
                x_dir = 1
            # Draw 3d box at soft limits for X, Y, and Z axes
            glVertex3f(x_dir * machine_limit_min[0], machine_limit_min[1], machine_limit_max[2])
            glVertex3f(x_dir * machine_limit_min[0], machine_limit_min[1], machine_limit_min[2])

            glVertex3f(x_dir * machine_limit_min[0], machine_limit_min[1], machine_limit_min[2])
            glVertex3f(x_dir * machine_limit_min[0], machine_limit_max[1], machine_limit_min[2])
...

fix for grid

glcanon.py

...
    def draw_grid_lines(self, space, (ox, oy), (dx, dy), lim_min, lim_max,
            inverse_permutation):
        # draw a series of line segments of the form
        #   dx(x-ox) + dy(y-oy) + k*space = 0
        # for integers k that intersect the AABB [lim_min, lim_max]
        lim_pts = [
                (lim_min[0], lim_min[1]),
...
            if self.is_rear_tool_post_lathe():
                x_dir = -1
            else:
                x_dir = 1

            glVertex3f(*inverse_permutation((x0, x_dir * y0, lim_min[2])))
            glVertex3f(*inverse_permutation((x1, x_dir * y1, lim_min[2])))
...

1.5. The part X axis extent bar is reversed

Fixed by Rogge

Created 2013/01/23, Kirk Wallace