"Transition" textures and flickering

[R Soul]

I've recently been seeing how well I can use a soft-edged grass texture to smooth the transition from grass to gravel. For example, take these screenshots of Essington:

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When building the track I have two choices: material blending or using the above approach. With blending, the transition is too soft for my linking. I know I can adjust the sizes of the relevant polygons, but that only works up to a point. So I've been trying to use a separate transition texture. The results have been quite good - via the texture I can make the transition both abrupt and smooth.

The problem is that from a relatively short distance the transition texture flickers out of view. I know vaguely why this is - it's polys are very close to the polys below it. Having looked at Essington and LeMans 77/79, I know that it's possible to stop the flickering. What I don't know is how. Does anyone know?

 

[Eric Tozer]

I'm guessing a bit here but I imagine if you steepen the join you will get less flickering. (see pic)

I suspect the Essington & other tracks use a different method.
Probably some blending in 3ds Max.
Another method you could try is extending the road width a bit & add a new texture on the edge that blends the dirt into grass in Photoshop.
Then you can just join the green bit to the terrain.
There will still be a join but less noticable.

Am i making any sense?

 

[R Soul]

I see what you're suggesting - rather than move the blend upwards, move the ground below it downwards. I'll give that a try.

I'd rather not make a texture added to the track's cross-section because that limits flexibility somewhat.

 

[R Soul]

Well, adjusting the angle between the terrain and the blend didn't make any difference, so the problem isn't the gap between the polys, but something else.

Following a hunch, I reduced the mip bias of the transition material from -2 to -4, and that made things look a lot better. I also use -4 on my track and -2 on the terrain to prevent blurring at too near a distance. Here's what I think it happening: The smaller mip images of the the texture are being increasingly dominated by the transparency, whereas the surrounding terrain textures, being fully opaque, don't suffer from the same effect.

So, thank you. Your idea may not have worked, but by ruling out the gaps between the polys, it did point me in the right direction.