Draw a preliminary sketch for your 3D sidewalk art using drawing paper and a pencil. Form a drawing with a strong perspective, which is used to create depth in artwork. Add colors to your drawing with colored pencils or markers.
Draw vertical lines onto your entire finished sketch that are approximately 1-inch apart. Add horizontal lines over the entire sketch that are 1-inch apart. This completed grid helps you transfer your original idea onto the 3D sidewalk art in perfect scale.
Count up the number of vertical and horizontal lines you used on top of your original drawing. For each 1-inch square, increase the scale to at least 5-inch squares. Choose a location on your sidewalk that accommodates this scale.
Draw a rectangle onto the sidewalk that allows for all the vertical and horizontal lines of your grid using a neutral color, such as white chalk. Typically the rectangle is just like your drawing but is scaled up. Add the same number of vertical and horizontal lines to your sidewalk rectangle as the grid on your original sketch. Each square is scaled up to at least 5 inches.
Fill in the top left square on the sidewalk with exactly the same drawing as the top left square on your drawing. Draw out the outlines of your sidewalk art first and then add the right colors. Each square correlates to the same square on your grid.