Spray (4e Variant Rule)
From D&D Wiki
The Spray range keyword is a nod to 3.5e's cone range for spells. Powers using Spray as their range extend outwards from the user and fill an area defined by the range modifier.
The following images are examples of the squares affected by a spray power.
A spray 1 extends outward one square and is similar to a melee touch attack.
A spray 2 extends outward two squares because the grid cannot support squares immediately in front of you.
A spray 3 extends outward two squares and then one square to each side from the main line.
A spray 4 extends outward three squares and then from the last two squares of the line there is another affected square to each side.
A spray 5 extends outward three and forms a triangle, near exactly as the spray 3 but with an additional layer.
A spray 6 extends four squares outward from the spray 5 to create an additional layer the same size the the layer added by the spray 5.
All sprays follow the same basic method to determine the area affected, each odd layer adds the outside bits to the layer, while the even layers are layers of the same size as the previous odd layer. Thus a change to the range of a spray effect may be very minimal or may be a near game changing effect. When homebrewing a power, remember that sprays larger than 6 or 7 can become incredibly destructive and may cause some encounters to be extremely easy if a player is using it, or if a dragon is using a breath attack with a large range he/she can easily destroy everything before him/her.
Converting Existing Powers
The most realistic conversion is the change of a dragon's breath weapon to a spray with the same range modifier. This may make the breath weapon less destructive, but if the attack is too weak, consider increasing the damage modifier by small amounts.