Euclid

An experiment to allow the creation and sharing of simple geometric constructions. When you have constructed a diagram, your slate can be shared by copying the browser's full URL.

by Alec McEachran, December 2015

Tools

Clears the current slate

Slate states are maintained in broswer history so this can be undone by going 'back' in your browser, as can other actions.

Move

Allows you to move vertices by dragging them. Free vertices can be moved anywhere. Vertices constrained to circles or lines can only be moved along their constrained geometry.

Add Vertex

A click on the slate will define a new vertex under the cursor. If you define the vertex as an intersection of two geometries, or on a particular geometry then the vertex will be so constrained.

Add Line, Ray and Segment

Defines a new line, ray or segment between two vertices. You can click-and-drag, or else click once to start the line and click again to complete it. Clicking near or dragging to existing vertices will snap the line definition to those vertices.

Add Circle

Defines a new circle by defining a center vertex, and a vertex on its radius. You can click-and-drag, or else click once to start the circle and click again to complete it. Clicking near or dragging to existing vertices will snap the circle definition to those vertices.

Add Vector Vertex

Defines a new vertex at an offset from another vertex. This is a 'vector vertex'; a vertex defined in terms of its anchor vertex and a fixed offset. You can click-and-drag, or else click once to start the circle and click again to complete it. Clicking near or dragging to an existing vertex will snap the anchor definition to that vertex.

Add Vector Circle

Defines a circle from a center and a vector vertex at a fixed offset. This circle will maintain size when the center vertex is moved. You can click-and-drag, or else click once to start the circle and click again to complete it. Clicking near or dragging to an existing vertex will snap the anchor definition to that vertex.

Remove

While selected, geometry that is clicked on is removed, along with any other geometries that depend upon it. Remember that this can be undone by using the browser's back functionality.

Animate

While selected, vertices that are not completely constrained will animate. Free vertices will move around the screen randomly, though will not change direction rapidly. Vertices constrained on circles will rotate around the circle clockwise. Vertices constrained on lines will move along the line but remain on screen.

When an animation is started, a separate 'stop' button is displayed. Animations will continue until that button is clicked, even if other tools are selected.

Trace

While selected, traces can be applied to vertices. This will draw the vertex's last few seconds worth of positions, until stopped.

When a trace is started, a separate 'stop' button is displayed. Traces will continue until that button is clicked, even if other tools are selected.