1. A computer-implemented method for executing a video game, comprising: receiving an input indicating to apply a liquid paint or a liquid thinner material to a first set of geometry in the video game, wherein the liquid paint or the liquid thinner material is rendered as a capsule held by a game character and wherein the input directs the game character to throw the capsule at the first set of geometry; determining a burst location on the first set of geometry where the capsule impacts the first set of geometry; determining a second set of geometry corresponding to a spreading effect of the liquid paint or the liquid thinner material from the burst location to an area of the first set of geometry, wherein the spreading effect of the liquid paint or the liquid thinner material is determined by a physics engine; merging, by operation of one or more processors, a first binary space partitioning (BSP) tree with a second BSP tree to create a merged BSP tree, wherein the first BSP tree represents the first set of geometry, wherein the second BSP tree represents the second set of geometry, of the liquid paint or the liquid thinner material, wherein one or more elements of geometry represented in the first BSP tree are associated with a respective paint/thinning state, and wherein the merged BSP tree represents a merged set of geometry created from the first and second sets of geometry; updating, based on the spreading effect determined by the physics engine of the liquid paint or the liquid thinner material on the area of the first set of geometry, a paint/thinning state associated with a respective one or more elements of the merged set of geometry in the merged BSP tree; and rendering the respective one or more elements of the merged set of geometry opaque or transparent based on the paint/thinning states of the respective one or more elements in the merged set of geometry.