Note this is an old article I wrote sometime ago in 1999 but rather than discard it I've included it in the tutorials section as there's some good reference links.

Recently I've been working on producing cloud, smoke & dust effects in 3DS Max 2.5 using plug-ins including Afterburn and Pyrocluster. Looking at clouds frequently & thinking about ways to produce them has led me to write my thoughts down, mainly to pass on my wishes to the plug-in developers & to open a discussion about ways of rendering clouds in 3DS Max. So far this article just concentrates on clouds, there are many more wishes for smoke & fire effects.

Cloud/Smoke production in 3DS Max can roughly be divided in to 2 areas

• Method of creation of particles for clouds 3D space
• Creation & Animation of Cloud volumes.

Some ideas for creation

• Vertex placement (with volume preview) - This can be done now in a round about way by having a particle array on a box (1 vertex only) applying Pyrocluster & having the shapes preview on & using a create vertex on the box, however I've found this to be a very unstable method in Max. Perhaps a new particle system that is create by clicking the mouse in 3D space. Pros: more accurate than a particle system, able to mould your clouds. Cons: takes a very long time to do, you can't change the scale of the particles/clouds

• Use a bitmap or gradient (similar to Matterwaves) either to generate the particles or control the cloud volume directly. Pros: more intuitive, should be much faster to work with, also ties in with Matterwaves. Cons: Could be slow to change, how to translate from 2D into a 3D volume.

• Have a new particle system type that would be able to create clouds of particles that had the characteristics/structure of real clouds, the way they flow & stream together.

• I think a combination of methods would work, a manual vertex/particle system adjustment/creation but only after setup using bitmaps first. Using them to have a bitmap/gradient 'quick start', you could then either scale up with the mouse a flat cloud (must be able to change scale axis position i.e. grow a symmetrical or hemisphere type cloud) or use the greyscale value of the image to pass onto the height of the cloud (darker the image the higher the value), another side view bitmap/gradient could be blended with the top view & used to create a 3D volume. These or other bitmaps/gradients should also be able to control the creation of the size of the cloud shapes.

Once the vertex/particle clouds are created in some cases you would need/want to be able to edit the particle cloud, similar to a edit mesh, employing soft selections methods & perhaps some way of painting rotation within the particles as well? Probably an even more basic method of single particle/cloud shape creation would be used as well, holding the left mouse button down left & right movement could control height & width with up & down perhaps controlling rotation, a good/quick interface would be need for this method.

Some ideas for creation of cloud volumes

• There needs to be a much more varied fractal cloud material types, I've listed at the bottom of the page the actual cloud types that occur in real life. Now I don't think we need to use all of them, perhaps only 4 to 6 new types. Identifying the most different types that are wanted by the users & feasibility by the programmers is needed . For example, long thin wispy types of cloud are just not possible to do at the moment & I'd like ways of being able to do them.

• The fractal controls in Pyrocluster appear to be limited to the single volumes that each of the particles create. This causes the 'cotton wool ball' effect where the look & motion of the clouds is just not believable. Would perhaps a metaparticle system of some kind in which the shape/volume of many particles became (where appropriate) a single volume instead be more appropriate?

• Another more intuitive way which I'd like to use would be able to blend with bitmaps/gradients different layers of fractal cloud types to form a new type. An example below using Pyrocluster, 2 fractal cloud types A & B, are blended with a simple greyscale gradient in two different ways, one where just the fractal clouds types are blended to create a new cloud type & another where the separate colour/shadow parameters have been changed & blended to create a very different looking cloud. Being able to blend, mix & match between fractal cloud types I think would give the user a very powerful tool to create almost anything they want.

• Other blending I'd like to see would be to lighting and shadow density/quality, you could also have a boolean type blending between layers as well, to avoid a very complicated interface you should be able to 'flatten' these to a separate fractal layer this way you could build your own cloud types & save them with a preview bitmap (beta testers could help provide a starting set perhaps?).
• Another options I'd like is one for sharpness of fractal type using direction of pickable lights, some clouds like this one seem to be much sharper/crisper from the direction of the light source.

• Also I'd like to see a level of detail/variable quality setting of the world step size based on either depth to camera (environment ranges), speed to camera (motion blur) or a user setting perhaps using a gradient/bitmap using either camera mapping or UVW on the particle system. This would speed up rendering and give the user control of where the quality was needed.

Cloud definitions & links from Australian Weather Photography web page, please note their Copyright notice.