Real-Time Terrain Modeling Using CPU-GPU Coupled Computation

Motivated by the importance of having real-time feedback in sketch-based modeling tools, we propose a framework for terrain edition capable of generating and displaying complex and high-resolution terrains. Our system is efficient and fast enough to allow the user to see the terrain morphing at the same time the drawing edition occurs. We have two types of editing interactions: the user can draw strokes creating elevations and crevices, and previous strokes can be interactively moved to different regions of the terrain. One interesting feature of our tool is that terrain primitives can be interactively manipulated similarly to primitives in vector-graphics tools. We achieve real-time performance in both modeling and rendering using a hybrid CPU-GPU coupled solution. We maintain a coarse version of the terrain geometry in the CPU by using a quad tree, while a fine version is produced in the GPU using tessellation shaders.

I. Introduction

Recent years have been marked with a striking evolution of sketch-based modeling tools [1], [2], [3], [4], which have the interesting property of benefiting greatly from real-time feedback while editing. As the object to be modeled increases in complexity, the modeling tool becomes more involving to develop. In the special case of terrain modeling, exemplified in figure 1, the challenge is to create in real-time realistic terrain features with intuitive strokes and guided landscape design. Fig. 1. Sketch-based terrain modeling example in our tool: as each stroke is drawn (left) or manipulated (right), the terrain is tessellated in the GPU to follow the stroke. In the CPU, the quadtree data structure (middle) controls the quadrilateral patches sent to the GPU.