1. A computer-implemented method for executing a video game, comprising: receiving input indicating to apply a paint or thinner material to a first set of geometry in the video game; merging, by operation of one or more processors, a first binary space partitioning (BSP) tree with a second BSP tree, wherein the first BSP tree represents the first set of geometry, wherein the second BSP tree represents a second set of geometry, of the paint or 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; and updating, in the merged BSP tree, a paint/thinning state associated with a respective one or more elements of the merged set of geometry.