We would like to share with you a small tutorial that covers how we used a Photoshop paint plus V-ray dirt technique to create the materials of our last year project FAUP Exteriors.
Hopefully this is the first of three tutorials. Another possibly describing how we used Rich-Dirt and other focused on VRay Distance Tex.
PS. The full scene ready-to-render is available to purchase in here.
It´s interesting to see how our clients react to dirt textures. Of course all depends on the situation: the client and the type work. Some clients come to us and request dirt as a must have, while others prefer to avoid it at all costs. Architectural competitions have more artistic freedom and so we can add a bit of dirt creativity to them. It can make your architectural objects look more real and most importantly, they will look more attached to the ground and become a part of their environment.
To achieve dirt realism there are many ways to do it. Below you will find an explanation about one of them.
GENERAL WALLS DIRT:
The same type of dirt work is made to most of the walls around the scene. A good map is download from CGTexture.com site and a long wall diffuse map is created already with a bit of dirt painted in Photoshop, mostly the top dirt of the wall. A V-ray Blend Material is created and a V-Ray black material is duplicated but with different V-ray-Dirt. One affecting the bottom of the wall, and another to increase the object ambient occlusion. In the V-Ray Dirt settings, the grey tone of the occluded color were used to tweak the opacity of the dirt overall. Placing a dirt bitmap in the radius slot provided also a bit more randomness and richness to the wall material. Having -5 in the Z bias made the dirt appear only on the bottom of the wall as desired. It takes quite a bit of testing and patient to get V-ray Dirt to appear the way you want. For most of this scene concrete materials, we used Falloff in the Reflection slot, both slots with the same map. Sometimes the bump map is just the diffuse map turned to monochrome, using Color Correction.
TOWER STUCCO DIRT:
For each face of the tower object we created different diffuse maps with dirt, painted in Photoshop. To make those tower face maps, we UVW rendered each template of the tower, saved them, and later on hand-painted the dirt in Photoshop using a combination of textures gathered from cgtextures.com. You can see below the maps used. Each face had a V-ray Blend Material. The basic stucco material of it had a composite in the diffuse slot. Composite layer 1 is the stucco material inside a soft color V-ray Dirt. While layer 2, with the painted dirty map, was set to multiply. You can also place this map inside an Output and adjust the contrast of it, or just play with the opacity values to achieve different results. In the same V-ray Blend, a dark green coat material was controlled by a V-ray mask containing a dirt map with radius opacity set to 50.
TOWER CONCRETE BASE DIRT:
Looking at the real building, one can notice that the base of the tower is composed with many concrete boards. For the 3D, we created each board with simple boxes and placed them correctly around the Tower. All of the boxes were attached into a single object and then Unique Material Plugin was opened and for each element is assigned a different ID for Multitexturing proposes. And so, the composite inside the diffuse slot can make use of the Multitexture plugin. Another layer in the diffuse composite contains a dirt map painted in Photoshop to affect the bottom of the concrete touching the grass. For this map, we gave a different map channel and proper coordinates to the object.
This is all for now!
Any question or doubts feel free to shoot!