According to an example, a 3D printer may include a delivery device and a controller. The controller may access a morphology of a part to be formed from a plurality of build materials in a layer, determine, based upon the accessed morphology, a first delivery pattern for the delivery device to selectively deliver liquid droplets onto build materials in the layer during a first pass over the layer and a second delivery pattern for the delivery device to selectively deliver liquid droplets onto build materials in the layer during a second pass over the layer to control a property of the part formed of some of the build materials in the layer. The controller may also control the delivery device to selectively deliver liquid droplets onto build materials in the layer according to the determined first and second delivery patterns respectively during the first pass and the second pass.