Why 2 tutorials for natural variations ? One for game artists - another one for architects ?
Because game artists need a much more weathered look.
Why are large scale variations so important for better renderings?
Without variations buildings look monotonous, less realistic.
Even adding tons of texture does not solve this.
In any case also have a look at the RTT tutorial, which shows how to bake RichDirt results to a texture.
What causes large scale variations in the real world? Buildings get a ´tint´ from weathering via wind. Wind is stronger at the edges of a building and at the top, with strong impact on dust, dirt, rain. This tutorial shows how to easily add this effect with RichDirt.
More Advantages of the approach described here are:
A copy of the tutorial model for mental ray is available here. For V-Ray click here. For RichDirt2 vr click here and for RichDirt2 mr click here. The file contains a simple scene. Simply click on the link to start the download (no registration required). Make sure you have gamma and LUT correction enabled for 3ds Max. Select Camera001. Render the scene:
Expert users can skip items 2 to 6.
Create a new Multi/Sub Object material. Name this ´myMultiSub´.
Name this ´myWallMtl´. (Note: to easily export from 3ds Max to your game engine you might want to use a 3ds Max standard material instead. Many exporters have better support for the standard material).
Add ´myWallMtl´ to slots 2,3,4,5 of myMultiSub. Make sure to use -instances- (not copy, we want the same wall material used 4 times). Note: add can be done via drag and drop in 3ds Max. Your ´myMultiSub´ should now look like:
Click the diffuse color map button, to add a RichDirt texture. The Material/ Map Browser by default opens the ´Standard´ folder´ - RichDirt had been found in the mental ray folder for version 1.01, 1.05, 1.06. Starting with version 1.1 RichDirt is indeed in the standard folder and can be used the same for mental ray and V-Ray. Name the new texture ´WallDirt´.
Green is used here so it is easier to see the effect. Also change the ´Clean´ color to rgb 0.973, 0.851, 0.612. Select the ´Rich Building´ preset.
Activate the ´myMultiSub´ material again, and select the 2 walls in the viewport. In the material editor press the ´Assign Material to Selection´ button.
If everything worked fine the image should look like below.
(except for the windows) but we still don´t have a ´large scale variation´ - the structures around the windows are identical all over
the facade. The building edges have also the same intensity top+bottom, left+right.
How to add the large scale variations ? The following part of the tutorial dives deeper into realistic weathering. Step by step. Game Artists tune a city with all its buildings - use RichDirt with the steps below to get as much extra effects as possible, for free when doing texture baking.
Our goal is to make it realistic, and we know that wind + rain + dust are the real forces for these variations. Click the RichDirt Radius map button - to add a Bitmap. In the 3ds Max Bitmap choose C:\Program Files\Autodesk\3ds Max 201X\plugins\RichDirt\wind.jpg. (The installation path is different for Max 2012, and for 3ds Max Design). You could also directly download the texture from the website (select it and right-mouse + save works in most browsers)
This texture needs to be applied in a way that it maps to the full facade, top to bottom, left to right. Typically select the main geometry, add a UV map modifier. Use box mapping, make the box match with the building, especially the upper edge should match. The -same- wind texture can be used for larger and smaller buildings - aspect ratio doesn´t matter here ! Render to get the following image:
What for ? The offset is to make sure the upper part of the texture isn´t completly black. Black would cause a radius of 0 cm (0 * 50 cm) , so inner occlusion wouldn´t find obstacles. Easy: Playing with amount and offset you can control how dirt is distributed over the building. If you weather several buildings of a city simply modify the rgb offset and you have a nice variation.
Create a 3ds Max composite map. Plug the existing (green) dirt in.
Add a second layer for streaks. Create a new RichDirt, select Preset ´Below Bench (strong)´.
Use red as its dirt color. Switch on inner occlusion (some of the benches are small so they are only
found by io rays). Make sure the composite mode is ´darken´. Render:
(If you want more details (= substeps) how to add streaks see the architectural tutorial step 11)
Hm, no streaks visible - what happened ? IO dirt covers AO streaks - We forgot to enable streaks ´For IO´ in the streaks rollup. Do that now. Render:
We get different shapes for the area below benches, especially top versus bottom.
This is exactly what we wanted !
Use ´Darken´ as mix mode for the composite map. Now render to check :
The easiest way is to take the clean color, make it darker and more saturated. We use slightly different colors for splashes and streaks to get a richer image. Also adjust glass (diffuse, reflectivity) to fit with weathered style. Mixing colors with the 3ds Max composite map can be tricky with the ´darken´ mode, it kind of requires that you indeed take dark colors for the streaks - which is good here as we want a really dirty image.
For really dirty areas in a game the ´Subtract´ mode can be interesting. Use black for ´clean´ and a gray value for ´dirt´ and subtract them from the main layer - the main layer needs a soft brown color (here 0.97, 0.67, 0.28) to get nice subtractive results.