Python CAD Tutorial 07 - Drawing a grid
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Python CAD Tutorial 07 - Drawing a grid

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Grid

We created a plane in the previous tutorial. Now we will inherit that class to create a grid, at a later stage we will add snap to grid functionality.The new grid class will take three parameters: a centre point, a spacing value and a size value. We will set the size value to be the size of the viewport and will set a default spacing between the lines.The new methods for the class are below:

Future tutorials will deal with snap to grid functionality and auto calculating based on the zoom level, but for now we have something to work with. 

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import math

from point import createpoint
from plane import createplanesimple


class creategrid:
    display_color = (0.6, 0.6, 0.6)
    
    large_grid = 10
    small_grid = 2.5

    def __init__(self, p1, spacing=1.5, size=65):
        self.plane = createplanesimple(p1, size * 2)
        self.p1 = createpoint(p1)
        self.normal = createpoint((0, 1, 0))
        self.size = size
        self.small_grid = spacing
        self.large_grid = spacing * 10

    def grid_spacing(self):
        #work out how many times the grid units fit inside our grid size and make it a whole number
        size =  math.ceil(self.size / self.small_grid) * self.small_grid
        #adjust x by size so we can draw the lines
        x = self.p1.x - size
        #loop from start until our lines are greater than our max size
        while x < (self.p1.x + size):
            x += self.small_grid
            yield x

    def draw(self):
        self.plane.draw()
        glColor3f(*self.display_color)
        glBegin(GL_LINES)

        for item in self.grid_spacing():
            #coordinate modulus large_grid (returns 0 if there is no remaineder), so lets draw a different colour line
            if (item % self.large_grid) == 0:
                glColor3f(0.4, 0.4, 0.4)
            else:
                glColor3f(*self.display_color)

            glVertex3f(item, self.p1.y - self.size, self.p1.z)
            glVertex3f(item, self.p1.y + self.size, self.p1.z)

            glVertex3f(self.p1.x - self.size, item, self.p1.z)
            glVertex3f(self.p1.x + self.size, item, self.p1.z)
        glEnd()