Render pass question and shader creation regarding texture maps

[evanmichalski]

Sorry if this was posted before, but I've always been wondering what the biggest difference between rawreflection vs vrayreflection, rawreflection vs vrayreflection, lighting, etc., and what are the advantages of using both when you are using them in post Photoshop?

 

Also, when creating reflection, specular, and bump maps whether it's in 3ds or Photoshop, what are the specific guidelines when creating them regarding the grayscale? I understand the process but I never quite understood how dark or light they should be, and maybe that's because I have trouble understanding color theory. But is there a technique or chart I can follow that can at least help me understand it because I really hate the trial and error process before I get the results I like.

 

Thanks.

[Chris MacDonald]

Sorry if this was posted before, but I've always been wondering what the biggest difference between rawreflection vs vrayreflection, rawreflection vs vrayreflection, lighting, etc., and what are the advantages of using both when you are using them in post Photoshop?

 

You want just the Vrayreflection, NOT the raw reflection. The VRayreflection shows the reflections as they would be in your scene; adjusted to take into account lighting, etc. The RAWreflection shows all of the reflections traced, even if the material is mostly diffuse, or they are in exceptionally dark areas, etc; and will thus show more noise, because vray wont have sampled anywhere near as much.

 

Try it for yourself, you'll usually see a noticable difference.

 

The chaosgroup documents are fairly handy too.

 

Also, when creating reflection, specular, and bump maps whether it's in 3ds or Photoshop, what are the specific guidelines when creating them regarding the grayscale? I understand the process but I never quite understood how dark or light they should be, and maybe that's because I have trouble understanding color theory.

 

It depends entirely on the effect you are trying to achieve, but the rules for a bump map are that white = a high point/extrusion and that black = a low point/depression. Mid grey (128,128,128) will produce no effect.

 

Specular maps are the same principle but applied to reflections and reflection glossiness. If for example you wanted part of your reflection map to be 0.8 glossiness in Vray then you would take the maximum value (255) and divide it by 100, then multiply by 80 (because 0.8 glossiness is 80%, as 1 is the maximum) giving you a value of 204.

 

I never go below 0.5 on my glossiness on any material as far as I can remember, so generally speaking I make sure that none of my specular maps have values lower than 128.

 

Hope this makes sense.

 

But is there a technique or chart I can follow that can at least help me understand it ecause [sic] I really hate the trial and error process before I get the results I like.

 

Then you're in the wrong job!

[jasonstewart]

For the maps I just make them from full black to white and use the color map in the bitmap settings to adjust the high/low as well as contrast. This is helpful when you want to use a single map for more than one parameter. Saves me from having to save over and over in PS to tweak, much faster IMO.