Historical Notes, Presentations


SDKsReal-time clouds with shadows




  • harris 2001 "Real-Time Cloud Rendering" (pdf)
    • Mark J. Harris and Anselmo Lastra, Eurographics 2001
    • presents a method for realistic real-time rendering of clouds suitable for flight simulation and games
    • provides a cloud shading algorithm that approximates multiple forward scattering in a preprocess, and first order anisotropic scattering at runtime
    • impostors are used to accelerate cloud rendering by exploiting frame-to-frame coherence in an interactive flight simulation
  • "Simulation of Cloud Dynamics on Graphics Hardware" - site, (3 MB pdf)
    • Mark J. Harris, William V. Baxter III, Thorsten Scheuermann, Anselmo Lastra, 2003
    • clouds are modeled using "partial differential equations describing fluid motion, thermodynamic processes, buoyant forces, and water phase transitions" !!
    • uses "flat 3D textures" - 3D data laid out as slices tiled in a 2D texture - to implement 3D simulations on the GPU
  • Swell"A Real-Time Cloud Modeling, Rendering, and Animation System"
    • J. Schpok, J. Simons, D. S. Ebert, C. Hansen, 2003
    • describes the software package Swell, an interactive cloud modeling tool, which produces "perceptually convincing volumetric cloud models that can be used in interactive systems or exported for higher quality offline rendering"
  • Dobashi"A Simple, Efficient Method for Realistic Animation of Clouds"
    • Y.Dobashi, K.Kaneda, H.Yamashita, T.Okita, T.Nishita, Siggraph 2000
    • proposes a simple and computationally inexpensive method for animation of clouds
    • realistic motion of clouds, shadows cast on the ground, and shafts of light through clouds
    • uses OpenGL for near-realtime rendering
  • j.p.lewisj.p.lewis
    • did some solid texture cloud studies (presented Siggraph 1989)
  • Geoffrey Gardner Geoffrey Gardner
    • as early as 1985, he was effective at turning simple ellipsoid surfaces into cloud volumes
    • Geoffrey Gardner, "Visual Simulation of Clouds," Computer Graphics, 19, No. 3 (1985), pp. 297-304
    • not much online information on him or his work
    • Send in the Clouds (1990) and Forest Fire Simulation (1992)
      • "Cumulous cloud development is simulated using fractal ellipsoids to model the clouds. The ellipsoids are positioned and scaled by a heuristic dynamic model based on the "parcel" theory, which describes cloud development in terms of air bubbles heated by external sources such as radiated terrain heat."
  • Ken MusgraveKen Musgrave
    • was a professor at GWU, then Director of Advanced 3D Research at MetaCreations; now has his own company Pandromeda
    • page on Modeling Clouds
      • goal is to combine realistic geometric models with a radiosity solution for the illumination
  • Paper at VRAIS '98:
    • Authors : Unbescheiden, Matthias and Trembilski, Andrzej
      Title : Cloud Simulation in Virtual Environments
      Abstract: In this paper we present a new method of simulation and visualization of smoke and steam clouds in virtual environments. We use a particle system approach but reduce the particle numbers to decrease the computation and rendering times. Special care, however, is taken for the presentation quality of the clouds. From every viewing point (even within the clouds) the VE user will not have the impression that the clouds are hollow polyhedrons, but rather fuzzy objects.
    • Trembilski worked on TriVis (below)
  • TriVisTriVis: Artificial Realistic Clouds Modelled by Simulation Data
    • Visualizing artificial clouds with a naturalistic appearance that are modelled directly and automatically by the simulation data of the numerical forecast model
    • In TriVis, fast and especially tailored fractal functions are employed for the generation of realistic 2D and 3D clouds that can be rapidly rendered by standard graphics hardware.
  • Fabrice Neyret at University of Toronto's Dynamic Graphics Project (DGP)Fabrice Neyret
    • Convective Cloud Simulation
      keywords: atmospheric physic, animation, big hacks
      I'm interested in simulating the formation and dynamics of convective clouds, like the cumulus (which can be extended to smoke).
      Beyond fluids local equations, that lead to costly 3D systems to solve, physicists characterize several structures at various scales in fluids, and their interactions, such as bubbles, jets, instabilities, waves, convective cells, vortices, etc. The idea is to use directly this knowledge to generate convective phenomena, like cumulus clouds and billowing smoke are. This allows to separate the scales: large bubbles account for large range air motion, while waves and vortices lying on a bubble surfaces are just locally advected.
      "I will sketch what a cloud is, especially a convective cloud like the cumulus, and describe 'how this thing works'. I'll give a rough idea about the local physics model that is usually used to achieve costly, physically-accurate simulations. I will then show some heuristic, high-level structures of various scales, like bubbles, instabilities, vortices, turrets, and hot spots. These structures yield some (almost) equation-free rules of thumb about how to animate a cloud."

Applications and products that support clouds

  • Bryce (non-realtime 3D)Bryce
    • latest version claims "artists can command clouds to roll by as the sun sets"
    • Bryce's "clouds" are only flat, continuous cloud layers
    • many options are presented for haze, cloud height, frequency, color, distribution, etc.
    • more like clouds: a feature called "localized fog"
    • consists of a object, such as a flattened sphere, with a "volume material" applied
    • by applying one of 37 supplied "cloud textures" and tweaking "edge softness" and transparency, you can get a decently realistic cloud puff
    • the most impressive cloud sample is a single sphere, with a grey marble solid texture and "edge softness" set to maximum
  • PyroClusterPyroCluster
    • a MAX plugin from cebas Computer
    • claims to do clouds, but rather does mostly steam and explosion effects
    • does allows shadows to be cast by, and cast onto, the cloud effects
  • TerraGenTerraGen
    • cloud layers are shaded using the direction of the sunlight
    • this gives the flat layers the appearance of being lit up correctly in 3-D, resulting in a very convincing sky
    • Hugo writes: "The secret behind Terragen's beauty: rather than going for all out brute force and mathematical accuracy, Matt just writes algorithms that produce good results, rather than trying to exactly model the physics. The clouds are essentially a beautiful bodge."
  • Visidyne CloudScape
    • visidyne"provides quantitative, radiometric, three-dimensional cloud rendering in real time"
    • very military-oriented
    • partnered with Paradigm
    • component products:
      • CloudGen creates databases describing the 3-D distribution of particulate mass density
      • CloudRad converts the 3-D mass density distributions into radiometric databases that describe the cloud surfaces and their radiative properties
    • seems to be SGI-only

Global Clouds