Some time ago I posted a tutorial about V-Ray 1.5, there was a part about proxy and I posted this image:
CLICK. There is about 2,333 billions of polygons. This is just a simple preview of proxy power.
Part 1: Theory You know what proxy can do now I will explain how it works. Proxy is an object that allows you to import mesh from external file at render time only. This can save a lot of memory while you work on your scene. For example, you have a lot of high-poly trees and you really don't need to see them all the time in viewport. By exporting them to V-Ray proxy you can speed up your workflow, and you will be able to render more polygons.
If you want to import mesh, you need to export it first. This is obvious. You can do this in 2 simple ways:
1. Select your object. Click right mouse button and in quad menu select: "V-Ray mesh export" option.
2. Select your object and write down in maxsript : " doVRayMeshExport() ".
This 2 ways will cause the V-Ray Mesh Export dialog to appear. Here is describe of options:Folder - of course in this folder will be saved your mesh.
Export as single file - When you export 2 or more objects this will merge them into one V-Ray proxy mesh.
File - name of mesh.
Export as multiple files - If this is selected V-Ray will create one file for one object.
Automatically create proxies - It will export, and create proxy. All transformations will be aved as wall as materials. But objects that you exported will be deleted.
Useful informations: - Remember that if you want export mesh it must be ready to render. You can't modify V-Ray mesh.
- V-Ray proxy you can find in objects list in V-Ray section.
- This is everything about theory. Now remember some usefull tips.
- When you want create multiple proxy of the same object it will be best way to create one and copy it with instance option.
Part 2: Proxy in use. Now I will describe how V-Ray proxy helped me in creating this scene (here is more than 500 mln of polygons).
1. At first i take one of models from Archmodels vol.31.
2. Now attach one object (trunk) to leaves. But remember to match materials ID's. This will create one multisub object material for tree.
3. Create proxy from this tree.
4. After exporting your object will look like this.
5. To copy any proxy you need to use instance option.
6. I created more proxies using this way.
7. For viewing proxies in viewport I prefer bounding box option.
8. Here you can see render if this trees. I put here one plane, physical camera and sky and sun system. More informations about this you can find in my last tutorial. Here is a
CLICK 
9. Here is an grass segment. As you can see it have a lot of polygons :).
10. I exported this segment to V-Ray proxy and created beautiful grass plane ;)...
11. After rendering it looks like this.
12. Here is attaching again of car that i merged to scene. This is very important if you wouldn't do this you will have problems with materials
13. Now just put proxies there where you want your car to appear and render.
With regards
Tomasz Wyszolmirski
Evermotion Team.
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