Re: Snow - Rain & Weather Effects

Superb Evan !

Resurrecting an old thread, but I just came across technique for handling snow over large areas by using displacement.  The original tutorial that I followed can be found here:

http://www.ronenbekerman.com/3d-snow-creation-tips-by-bertrand-benoit/

If you're looking to do realistic snow over a large area, the easiest way to do it is to create a displacement map that specifically for the area where you want more details.  This scene is a very simple example since it's essentially just a square b-spline surface that I attached a square displacement map to, but you should be able to make this work on any kind of terrain.

There are a couple important things to remember when you're creating your displacement map:

- Make sure your map is 16-bit.  This will help create smoother gradations and cut down on the classic stairstep effect that can come from using a low res displacement map.

- Start out with a 50% gray background.  If you're using SS3, you should set your high and low values to 50 and -50 so that you can create both raised and sunken areas that don't stick out beyond what you would expect.  If you're using SS2, then you can always start with a black background but you're limited in what you can achieve with your map.

The map that I used for this image is just a 2000x2000 16-Bit PNG:

For this image, I had MicroStation do an ambient occlusion pass as well as the normal Color & Alpha and then blended the two passes in Photoshop to help pull out some of the details. 

The raw image from Luxology looks like this:

And the Ambient Occlusion pass looks like this:

Blending the two can really help pull out the details and give the snow more of an authentic, dirtied look.

Feel free to give it a shot and post your results!  I'd be happy to answer any questions about this process as well.

Hello Kurt,

I look into this,

Thanks you,

Fabrice

Fabrice:

Hello Kurt,

Very interesting ! Can you post the configurations ?

Thanks,

Fabrice

sorry for the late follow-up:

Have a look here

hth

Kurt

Wow, great work, as always!

CP

Weather effects like rain are much easier made in post production in Photoshop.  But it should be simple to make a realistic wet asphalt material.  here is a quick test:

http://vimeo.com/groups/microstation

the snow material works fine, but I'm not sure it will be very useful in a complex model. The problem is of course the parts of the object s that are not covered in snow.  In my examples I have hosen a metall-like surface for these parts in the material, and this can be changed into almost anything, but what you really need is the original object/material to be visible.  This can be done by making a snow material that leaves the non-snowy parts invisible.  But then you will have to clone (duplicate) all elements that are supposed to be coverd in snow...

Holy smokes, that is impressive Kurt.

You're litterally sugarcoating it.

I see. thanks

p.

The light leak is a displacement issue.  There is only a few millimeter displacement in use for the snow, but the low sun reveals one of the expanded cracks

Kurt,

the bump algorithm was rewritten in new engine, thus the difference I guess. out of curiosity, what is that light leak on the left front car fender?

p.

Thanks kurt´s, by the images that we samples, the light also greatly improved in the ss3?

there are som differences that I don't understand between ss2 and ss3, like the slope area and bump behaviour, but it works in both versions.

A bit off topic, but the slope gradient can also be used to control grass growt (avoid grass on vertical surfaces):

Great comparison.

same file (same settings) opened and rendered in SS2:

ok, I did not try to open the file in SS2, but I guess it should work just fine then.

I used the slope gradient in multiple channels, like displacement, reflectance (inverted), color and in an extra darkening layer for the bump map.

That looks fantastic!

Thanks for bringing this function under our attention. I wish the (new) procedurals where less hidden. It are great new functions, now we can add intelligent materials.  

B.t.w. I just checked Ss2 and there the slope Gradient is already present. 

Hello Kurt,

Very interesting ! Can you post the configurations ?

Thanks,

Fabrice

I've been experimenting a bit using procedurals - a slope gradient procedural to be more precise (SS3).  Not saying that this attempt is a realistic looking snow, but it might be an interesting track to investigate further.   Needs a lot more tweaking before you guys are convinced, I know! 

There is only one material in this scene:

A while ago I did a couple renders using clearcoat to make wet roads and when combined with volumetric lights for headlights and some fog, it creates a pretty nice rainy evening effect.

If you want to give the wet roads a shot, feel free to grab them from Entourage!

http://communities.bentley.com/products/microstation/microstation_visualization/entourage/m/entourage-gallery/64865.aspx

though I haven't used it (yet), wouldn't the "ivy" tool that I've seen demostrated produce a snow effect? You would have to define the 'leaves' as something larger and white, but the pillowed effect that follows geometry would be nice.

It probably wouldn't work for the large civil scenes discussed, but in close up scenes it would be too taxing. It would be actual geometry, not an automatic effect though.

my oldies :)  ms luxology

http://www.youtube.com/watch?v=UZwW0yRHjZk

feel free to use in christmas time :)

Hello,

this is a good example what is possible to achieve in 3D software.

www.peterguthrie.net/.../snow

And here is a plugin that would be an inspiration for Bentley:

www.zwischendrin.com/.../107

3D Winter trees:

rendering.ru/.../itrees-vol3-winter.html

Please look at Gallery - amazing!

Regards

Greg

"To build geometry for every blade of grass, leaf and pine needle is a highly inefficient way to do things".

I totally agree. But there's allways a way to bypass these kind of things. Lets say a treshold. Remember that rendering every fur strand can be 'inefficient' as well, but there are options like 'adaptive sampling' that make it work nevertheless.

Using only maps would make Photoshop hell and has little flexibility when using surfaces that are partially obscured from snow. At least compared to an app that does the job for us. And it would hardly allow to make picture like these (flickr photos)

www.flickr.com/search

www.flickr.com/.../3269092861

till we have a snow and rain app you can try this.

To build geometry for every blade of grass, leaf and pine needle is a highly inefficient way to do things.  Proper use of bit maps, alpha channels and post render editing go a long way in speeding up the process.

I tried using the luxology fur with really fat fur tubes. But this does not allow tubes to be fatter than their spacing. It creates a saucage forrest instead.

I think a 'snow engine' would be cool (pun). I guesse calculating where snow should be is not much different than occlussion in a scene with one light source and direct rays only. And snow can be substituted with wetness/dust/volcanic ash/moss/fur or pretty much any texture. Some idea's on the rendering process.

#1 Calculate surfaces that face upward, according to a certain 'snow angle' (somewhat similar to solar angle).

#2 Calculate wich parts are not shielded from the sky by geometry.

#3 Accumulation angle. At what angle will snow no longer stick to a roof/branche.

#4 User defined occlusion/reduction? I guesse this could be a map. User defined parts that are free from snow. The parking spot where a car has just moved; a spot on the roof where a snowball has roled down; tire tracks; etcetera.

#5 Material defined occlusion. Toggle to define if a material is receptive to snow.

#6 Render the snow as a seperate material.

Nice... but the samples here are pretty small scenes.... Have a peek at this paper for a flavour of the type of scenes I think Mstn will need to deal with, especially in the civils or geospatial markets.

Will Mstn rendering controls look like Terragen 2, one day?

Even Modo, which Mstn rendering is based on, struggles with big scenes. If I understand the posts, the trees had to modelled in Vue Infinte and imported into Modo, and multi resolution replicators had to be used to keep the scene manageable. Please note the problems with manipulating the replicators.

I think Bentley should be thinking ahead... with Luxology. It seems to me that we will all run into the need to handle 'big scenes' that will be terrain or urban in character.

A plugin like SnowFlow would be great!

The snow reminded me of something. I thought I would share it. Attached is scan of a print I have done by Ken Stopker, an old friend of mind. I wish I had the original file because it looks 10X better than this scan. This was modeled in MicroStation and rendered with ModelView...... about 20 years ago! Just a reminder it's not just the tools, its the person using them.

all high-end application do such things via rendering plugins / shaders - as procedural textures created during rendering only. there is no reason to have real geometry in file for such things ....

www.zwischendrin.com/.../107

p.

Hi Robert,

Yes..... it would be interesting to see where Luxology will go with this, long term.

There seems to be two kinds of rendering packages at the moment:

1. General packages like Luxo, Max, etc which are polygon tessellation based.

2. World or environmental modelers like Terragen, Vue Infinite, Bryce etc, which are more procedural and LOD aware.

The second category must be relevant for Bentley due to its heavy presence in the Civils and GIS fields. The general apps aren't really geared to handling the larger datasets or specialised rendering techniques.... Lots of mention of heightmaps, hierarchial spatial data, instancing, billboards / imposters, procedural materials and objects, particles etc.

Point Clouds...

Maybe Bentley should get Luxology and Pointools to talk. Point clouds, voxels and meshes, seem to becoming a focal point for dealing with large 'terrain' or 'foliage' type data. I think Luxology is still to offer particle-based rendering, so maybe this is the time for Bentley to make sure its long term requirements will be served.

1. Point (Particle?) based rendering is a way to manage large datasets by controlling LOD and deferring rendering. Typical approach for terrain modeling / atmospherics rendering.

2. Storing global illumination as point clouds is a way to speed up rendering. Lighting has always been a big time eater.

3.Point clouds look like they are becoming a cheap way to capture as-built data. Data that will be part and parcel to CAD sessions, like raster and texture info.

This an example of how point clouds could act like 3d rasters.

This is paralleled by the way the latest photogrammetry tools like Phidias, PhotoSynth3d, PhotoFly, PhotoSketch, Photomodeler, Insight3d all generate point clouds as an interim product.

Photos and laser scan point clouds can even  be combined to produce fully textured 3d meshes, based on the 3d info, colour info from both the scan and photos or video  footage, maybe even rendered using splatting techniques with the photos providing interpolating texture patches? There are even hardware assisted techniques that avoid meshes, which need to be adapative to keep things scalable.

We CAD users tend to be insulated from the messy non-vector 'real world', until we need to render something, which usually mean having to insert something into a larger noisier context. Curiously, this is where all that engineering information and thinking starts to morph into 'illustration'. I guess this is changing.

Regards

Dominic

With all the snow in London at present it actually got me thinking, has anyone dabbled in any kind of weather effects?

I'd be interested to know what people have achieved in regard to rain and snow.

I regularly have to do renders of buildings in parts of England where we don't have Miami like sunshine but instead it rains 90% of the time and it would be nice to show something atmospheric.

I'd guess most people do these type of things in Photoshop post render but surely snow and puddles must have been done in Microstation before?

Thoughts?