Model / BAT problem - comb effect

[Broonie 21]

I'm currently experimenting with lotting, namely creating large BATS that act as base layer then adding props on top to create 'dioramas'. In the image attached, everything you can see that's the 'ground' (grass, paths, parking lot) is one big model (saved as a prop), raised 0.151m so shadows will be cast.

To save time and have more flexibility, I'm trying to have things like driveways, paths, parking lot markings etc. as props, so they can be moved around in the LE without the need to re-build and re-render the whole base model every time I want to widen a driveway or add a new surface.

The problem I'm having is that if I raise the path all the way to 0.29m, the threshold for shadow casting, I get the dreaded comb effect as shown in the screenshot. There's a ~0.15m gap between the base prop and the driveway prop, so this obviously isn't enough.

I've tried changing the props exemplars to true and false for 'is ground model', I've tried sinking the base model and I've even tried spam plopping tons of driveway props to try and cover up the combing

 

Anyone out there experienced similar or knows of a workaround?

 

@Jasoncw I'm looking at you, o wise and ever helpful one 

[Jasoncw 11,941]

I would love to know myself!!!

I made such props for Nofunk's One Detroit Center BAT, the tree planters, and on my old computer they looked beautiful. And now on my current computer I get the same problem you're getting.

As far as I know, we've done everything right, and it's an issue with our graphics cards, but I don't know what or how to fix it.

[Broonie 21]

So as if by magic, I've managed to solve my own problem 

I realised that the only reason the base model needed to be raised 0.151m is because of the base textures... so I used ilives reader and this tutorial to remove the base textures from the lot.

This allowed me to drop the big base model prop to 0.00m when rendering. I kept the driveway prop at 0.29m, and what do you know, it doesn't comb anymore.

Back to lotting!

[rsc204 21,863]

The effect you see is down to z-fighting, where the GPU doesn't know what object to give priority at the same height and so it flickers between them. I know the NAM team previously ran into this problem, where some users had GPUs that could handle such effects, but others not. I believe there was a change in how GPUs handle such objects at the same height within the DirectX specifications. SC4 isn't compatible with this change, so unless you have a card/drivers with the old specification, the issue appears. Hence newer hardware tends to bring the problem.

I would say however, especially for smaller BATs such as residential housing, using models as the base comes with many drawbacks. The biggest one being an almost complete lack of any slope tolerance. Since for the most part, the exact same effect can be achieved with a handful of lot textures, I would recommend you reconsider your approach. LE textures will make such items vastly more flexible.

Also, I have experience with this from making my overhanging fillers, you'll need a minimum height of .2m for such a prop/model, to avoid the z-fighting with lot/network textures. You can use SC4 Model Tweaker to adjust the height of a model, no need to re-render it. Since it looks like the driveway is intended to extend over the Street/Road textures to meet up with the carriageway, it wants to be .2m off the ground. Much higher and the isometric perspective of the game will give the effect of the prop being moved on the X/Z axis (Y is height in SC4). You can compensate for that by making a piece larger than it actually needs to be, around .1m - .2m at each extremity. Although for the driveway at least, that shouldn't be necessary.

[Broonie 21]

Thanks for the explanation!