#subtract

1fn subtract(inout self)

The subtract function modifies the current shape in the Sdf2d drawing context by subtracting the previously stored shape from it. The result is a new shape representing the area of the current shape minus the overlapping area with the stored shape. This operation is useful when you want to cut out a portion of a shape using another shape.

#Parameters

• self (inout): A reference to the Sdf2d instance. The function modifies the internal shape and old_shape fields of self to reflect the subtraction of the shapes.

#Returns

• void: This function does not return a value but updates the internal state of self to represent the subtracted shape.

#Example

1fn pixel(self) -> vec4 {
2    // Create an Sdf2d drawing context for the current viewport.
3    let sdf = Sdf2d::viewport(self.pos * self.rect_size);
4
5    // Draw the base shape: a circle centered at (50.0, 50.0) with a radius of 40.0.
6    sdf.circle(50.0, 50.0, 40.0);
7
8    // Store the base shape for subtraction.
9    sdf.union(); // Store the current shape.
10
11    // Draw the subtracting shape: a rectangle overlapping the circle.
12    sdf.rect(40.0, 40.0, 20.0, 20.0);
13
14    // Subtract the stored shape (circle) from the current shape (rectangle).
15    sdf.subtract();
16
17    // Fill the resulting shape with a solid red color.
18    sdf.fill(#f00);
19
20    // Return the final color result.
21    return sdf.result;
22}

#Explanation

In this example:

• Create Drawing Context: Initialize the Sdf2d context using the current position and size of the viewport.

• Draw Base Shape: Use sdf.circle(50.0, 50.0, 40.0) to draw a circle centered at (50.0, 50.0) with a radius of 40.0.

• Store Shape: Call sdf.union() to store the current shape (the circle) in self.old_shape.

• Draw Subtracting Shape: Draw a rectangle overlapping the circle using sdf.rect(40.0, 40.0, 20.0, 20.0).

• Subtract Shapes: Use sdf.subtract() to subtract the stored shape (the circle) from the current shape (the rectangle), resulting in a shape representing the rectangle minus the overlapping area with the circle.

• Fill Shape: Fill the resulting shape with red color using sdf.fill(#f00).

• Return Result: Return sdf.result, which contains the final rendered image showing the subtracted shape.

#Notes

• Shape Composition: The subtract function allows you to create shapes by cutting out parts of one shape using another. This is useful for creating holes, notches, or complex silhouettes.

• Order of Operations: Ensure that you store the initial shape using sdf.union() before drawing the subtracting shape and applying sdf.subtract().

• Transformations: You can apply transformations like translate, rotate, or scale to manipulate the shapes before subtracting them.

• Combining Shapes: The subtract function is part of a set of Boolean operations that allows you to combine shapes in various ways. Other related functions include sdf.union() and sdf.intersect().

• Further Effects: After subtracting shapes, you can apply effects like sdf.glow() or sdf.stroke() to enhance the visual appearance.