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Texutres: What should Multiply and Add images consist of?

Discussion in 'Bob's Track Builder' started by R Soul, Jul 9, 2009.

  1. I understand the basic idea of multiply and add maps - they make it harder to notice the texture repeating itself when tiled over a large area. What I don't understand is what each image does and how they should be made.

    I've looked at the maps for the default grass texture and I can see that Multiply is a greyscale image. How it should be made for best results? Should it be based on the Diffuse texture (if so, how?), or will any greyscale image suffice? Is it correct that grey pixels in the Multiply map lead to the pixels in the Diffuse map being lightened/darkened?

    I've looked at the default grass texture and the multiply map uses very light shades of grey. Is it the case that darker shades of grey would really hide the tiling effect but would also make the texture really dark, so a compromise must be made by using lighter shades of grey to disguise the tiling to some extent but still allow the texture to be seen?

    And what does the Add map do? In the default grass001 texture, it's mostly transparent, and what little opacity is there is too hard to see.
  2. i think the multi map can have colour, but just don't put too much in because it will show up 'multiplied' by the diffuse texture. so maybe some almost grey splodges of an earthy brown for mud or dry patches and a slightly different green as well as the regular grey noise would give some nice effects. it looks best when you can stretch it out (tiling less than 1.0). that's when you get larger, more general changes in grass tone that can hide the seams in the diffuse map. you can also use (i think) an aerial shot of the track, or just certaint sections of the track as a multiply, similar to blending the background image in btb, but the colours might be quite vivid. the solution is to desaturate the multi-map, unless you like to get psychedelic. it's the same as multiply blending options in photoshop layers and tools. eg. if your diffuse map is all 128 grey and your multi is 255 red, you'll have a washed out red sort of material. a yellow diffuse and blue multi should give a green. it's colour mixing. it just so happens that the diffuse map is generally what we want already and we just want to spice it up a little here and there, so use a mostly grey scale map.

    you could base the multi on your diffuse, but if you keep them at the same scale it is just wasted. you could open the tiling so the multi is repeated say, 4 times across your whole track, so the general grass tone might change every 50-100 meters or something, which is the sort of thing that happens in the real world. The Lonley is a big supporter of the multi map. check out his tracks like Putnam Park for an example.
    http://rfactorcentral.com/detail.cfm?ID=Putnam Park

    in a multimap, a 128,128,128 grey would probably not change the diffuse tone at all. the magic happens either side of 128, so yes, lighter or darker tones in the diffuse. the multi doesn't cover the diffuse at all, it changes it's colour. it's still very important to have a 'seamless' grass texture. multi just changes it's colour content in an independanty definable way. you will always see a bad diffuse tile, so start with a good diffuse map.

    Multi maps, along with BTB blended GEarth images really are critical in getting a good realism into a track nowdays. avoid them at your tracks peril.

    i think the add map just adds highlights to the diffuse. white is highlight, black is 'null'. not sure how a non-grey scale map would look, you would have to trial and error with saturation and brightness i guess. i have the add scaled smaller than the diffuse (1.0+) so the diffuse isn't as critical in the detail stakes, which means, if you like, you could open up the tiling of the diffuse a little more which would further reduce the seam effect. The add map is kind of like a constant specular map, in that it doesn't really matter which angle the sun is at, it still shows highlights.

    i think i wrote this in another thread but the way i would have it all set up is:
    diffuse map, main grass texture, tile: 1
    multi map, mostly grey scale noise with a light dusting of brown, tile: 0.1
    add map, darkish greyscale, lighter grass type pattern, tile: 2 to 4

    when you blend a background image in BTB to 100%, the add map will still show over the diffuse, and come to think of it, the multi might too. this is good if you are working with G-Earth images because, depending on your track, they are fairly lo-res, so the extra detail and noise is a big help.

    it sounds like you've figured a fair bit of that out already, but for anybody who reads this, multi and add maps are good. really good. use them. start with the default ISI maps from mills or toban or something to see what they look like and how they look ingame. end of ramble.
  3. to try and make sure i've answered your questions rather than rambled about the place...

    any grey scale or colour image that is of the 2,4,8,16,32,64,128,256,512,1024,2048,4096pixel series dimensions.

    yes, light= lighter, dark=darker. they don't mask out the grass map though, only change it's tone.

    nope. it's not lighter or darker that hides tiling. the multi never obscures the original map, it merges. it's the way the lighter or darker bits spread across the area of several tiled grass textures to create what appears to be a bigger texture.

    yep, the smaller white bit/light grey bits are the highlight details. tile them smaller than the original map so it looks like your grass map is higher resolution.

    so, multi and add make your grass texture look larger and higher resolution.
  4. Is there a tutorial about good textures on your track? My track looks rubbish in terms of textures and I don't know where to start to improve it, I'm lacking the basics to make sense of this thread.
  5. this is a few years old and more geared towards 3d studio max, but lots of it can be understood in terms of btb.
    http://www.thepits.us/files/tutorials/ISI_trackbuilding_04.pdf (page 4 doesn't seem to work)

    not so much about making textures, but more making materials i think. a help none the less

    as far as textures go, the best textures are almost, if not always directly from digital cameras. take a good, square on shot of the surface (grass, bricks etc) in similar light conditions to your track (and time of year, as funny as it might sound, the seasons do impart different ambient lighting). from there, do your best to make it seamless. there was recently a tute here on seamless textures from another site.
  6. Thanks woochoo. Now I can start experimenting with these things.
  7. no worries. it's good stuff once you get it working.
  8. Ok, kind of doubleppost.. I asked a thorough questoin couple of minutes ago: http://www.racedepartment.com/bobs-track-builder/62459-diffuse-multi-add.html#post901926

    So multi/add is there only to break the pattern? No changes in direction of view or light? So basically, i could just make larger grass texture like this( diffuse 2x scale, multi layer 1x and add layer 8x) and to burn it with photoshop and use a large (4096) texture instead of three layers of 512x that need to be real time calc?? Is it really just there to make small patterns not appear tiled...Weak and waste of resources if so... Our GPU cards can take a lot of textures/materials now that we have 512-1gb of memory and that doesn't include texture memory...So why not make one large texture and avoid the calculations of three smaller layers, that processing power is needed elsewhere anyway.. Our GPU's start clogging in about 300-400mb of stuff in it and most tracks will take about 100-150mb of GPU memory.. So why, in the name of science, should we use multi/add?

    EDIT: About photographing your own textures: snap at noon, the tint is minimal (suns angle causing coloration affected by time of year & latitude) and the shadows are shortest. Try to angle the camera 90 degrees angle from the ground (sun behind your back or vice versa, keep the same procedure thru the session!) Tilt, pan and roll even at slightest amounts can ruin a good texture cap. But all those instructions aside, if you see an inspiration thru your viewfinder, everythings allowed....After all, you know what to do with it.

    Vertical shots are more harder, you may need to check the location thru all lighting conditions during the day and find what suits the best. The less sun rays have to travel to hit the object and reflect thru lens to be captured to film/cell the better. Good way to soften shadow is to have a person hold up a reflective surface (aluminium foil, white sheet etc) to shine that natural sun against it self (sun coming from south = reflective surface pointing south), a common trick in photoshoots and cinematography and possibly the only trick to get good vertical closeup shots. Just don't overdo the reflection, it flattens the image, think sun 80%, reflection20%.

    EDIT2: Oh, usually overcast days are shunned in business, texture capturing could be potentially best at that time.. Shadows are non existent and digital color correction easily gets rid of that blue tint...