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Diffuse Multi and add

Discussion in 'Bob's Track Builder' started by ebrich, Aug 18, 2011.

  1. ebrich


    I've been wondering, for a while, why my addon textures, especially grass based, always looked different against the default grasses and having seen your terrain work mianiak and read your comments I searched for more info. Came across a thread from 2009 between R Soul and woochoo which put it into perspective. Thought best way to learn is take apart a default grass, with multi & add, and put it back together. Did that but ended up with just the diffuse texture (thats what it looks like) in BTB. Sort of sparkles.
    I have the 3 images - diffuse - multi & add loaded into XPacker and they are listed together in Textures. I made the latter 2 half size of the diffuse.I tried with alpha trans and chroma and I have saved textures in DXT3 and DXT5. What settings are used to get this all together please. Or am I barking completely up the wrong gum tree?
  2. Chroma and alpha are for textures like fences and trees.

    I decided to see what info was on the internet, so I typed in 'Diffuse multiply add' into Google and the first result was that 2009 thread. I just did some experimenting and it helps if you've used layers in things like Photoshop, PSP, Gimp etc. You'll have seen the various layer blend modes, two of which are Multiply and Add. They do the same thing in your graphics program as they do in game.

    The games don't seem to make use of the mult or add maps having transparency in them, so there's no point using DXT5. I'm not too sure about the difference between dxt1 and 3, but I think it's quality (and file size), so dxt1 should be fine.

    If both maps are greyscale, the lightest parts of the multiply map have no effect on the overall colour, whereas darker parts make the grass darker. In the case of the add map, dark does nothing and light brightens up the grass. The add map is very powerful. Even the most subtle shade of grey will make your grass look garishly bright. That's probably why the default add map is transparent - to make it black. So bright mult maps and dark add maps.

    In XPacker/Venue materials you can play with the Scale values, using the original values as a starting point. I could go on but it's best to just experiment using a test track. It's also quicker to use Venue Materials rather than XPacker when you're just trying things out.
  3. ebrich


    Many thanks R Soul for lighting my way - yet again.
    I've never had the honer of tinkering with layer blend modes so now I understand the multi-add tutorial that mianiak put out. Great. Also found some blending tuts on Google-Photoshop.
    One piece of the puzzle starts to bring it all together and I might at last be able to get some decent terrain textures made that don't glitter as you move past them.

    View attachment terrain diff01.7z
  4. I still don't get it. If multiply and add just enchance the existing diffuse, why don't i permanently do it in photoshop? I mean, if it is just multply & add without any of it's shading applied at different distances or angles... What exactly changes when i look at that face from distance of angles? I've done some tests but still don't know what you can gain from that shader... But if, like i want it to be, it adds different parts when in certain angle/distance and multiply when at a different angle/distance there's some reason for it. In that case, please explain as no explanation has provided me with any info of what it actually does... Just saying "whites become more white and blacks become more black" is enough to state that i can use levels in PS to that texture instead of GPU trying to do it realtime.

    I've tried to google this answer but every tutorial says the same: it contrasts the texture but no where it says when it does multi/add to anything.. I can't believe that it is the same as me adding a multiply/add layer in 2D, that doesn't make any sense.

    So please, any one that has this knowledge explain "again": i look at a face, normals pointing straight at my face, light behind my back, what does it look like? And the same when looking at 45 degree angle up, light stays the same. And 45 degrees looking down. I've tried and either it is a fault in my eyesight but levelled (more contrast) diffuse map looks the same as nonlevelled diffuse/multiply/add..
  5. Kennett, http://www.racedepartment.com/bobs-...-blended-background-image-btb.html#post892195

    The way add and multa maps are used on grass with gmotor is usually in most cases a larger diffuse image of the grass with add and multa enhancing it when getting close up. If you simply just did this effect in photoshop then you would not see the finer detail in the game.
    You will find most tracks use this technique. Pretty well much all of isi's tracks do, and it doesn't have to be a really large image like I used in Sears, it can be smaller. If you have simed, check out the ISI tracks.

    R Soul, The alpha channel in add maps I found I only had to use it when I used them on the track edge blend. Otherwise they don't need alpha. *multa doesn't need alpha for edge blend, which has me confused, but that's the way it is :D
  6. Ok thanks a million! The three words "getting close up" explain it so that i understand it.. Distance related, makes sense that multi/add exist now. Those pictures a great but really didn't tell me anything as i can't recognize the bit of track in the closeup, ie don't know where it is in the big picture.. But i got it now and can move on to test it now that i know what to look.