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Registered: 01-2012
Posts: 567
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Bump Mapping and Bump Scaling

I helped on the Golden Gate track when it was suggested that a row of tires that was present in the track needed to be felt when you ran over them. I jumped on that because I wanted to try a solution of using X height manipulations. While it worked, it was not very elegant and required a bunch of track segment splits to support the X sections.

I wanted to figure out Bump Mapping - and I think I am on track. I've read everything about BM/BS (Bump Mapping / Bump Scaling) and put some things together on my own. I did a track that has a series of esses with tires similar to the old Riverside track (North Point CC). I didn't want to put in dozens of segment splits to accomodate the X section settings as required on the Golden Gate effort, so I did this with Bumpmapping.

The picture is of this section of track but can be confusing, let me make it worse by trying to explain it.
(The track direction of travel is Left to Right in the image.)

The section to be bumpmapped must be assigned a type that supports Bump Mapping. Of the twelve available type choices I have verified Concrete, Asphalt, Paint, and TrainTracks(!) do work. Rumble, Grass, Gravel, Sand, and Dirt do not work. That leaves Inaccessable, Invisible, and Water. These three remaining types are mysteries and I have no idea what they are for. Water will render your car immobile if you come to a stop in it.

My current working theory is any Material type that has a predefined "roughness" value overrides any BM/BS setting. Grass, gravel, sand, dirt, and rumble have a predetermined feel when you drive over them, always the same, regardless of Bump Mapping or other track variations.

I created a type of channel where the bumpmapping was to take effect. I wanted it to be very severe due to the buried tires. From the top down, the first BM line sets the BM value for the track area to the left of the direction, the grass area at the top. I don't think this is needed since grass can't be bumpmapped but I left it in because it works as is.

Next, I added a Bumpscaling line and set it to 5 for both Scale Params - Head and Tail. 5 is the max setting that will save when you save the track in Sandbox. You can set the value higher, but when you reopen the track it is set to 5 again.

Next line down, the BM car killer line, I named it Tires. The values are:
1 200.0 1.0
2 150.0 2.0
3 160.0 3.0
4 170.0 4.0

Next down, another BM line with Track Default selected, to put the track itself back to normal. Track Default is the general common setting, I did not modify it from that.

Finally, the section where the tires are located is set to Asphalt. As the track goes from left to right, this F section controls the zone where the tires and bumpmappng lines are.

So, if you go completely to the left of the tires, in the grass, it feels like grass. Stay on the track, it feels like asphalt. Stray into the tires, hold on. It feels like you are really doing damage to the car underneath, and if you hit them at a bad angle, you will bicycle.

Something to be investigated --
For some reason, BM and BS seems to work differently if it is to the left of the track CL or to the right of the track CL. It may be related to how sandbox works when building a track segment from the inside to outside.

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1/27/2013, 6:52 pm Link to this post PM amtronic Blog

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