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Land Impact Issues


Interregnums
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Hi there,

I have made a corrugated iron roof that i would like to bring in world.

Howeever it's a few hundred land impact. I have made sure to not make too many faces, and it's not the smoothest thing in the land.

Is there a way in blender to make things less heavy so they don't explode land impact numbers in SL?

 

Cheers

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Please tell us how many triangles and vertices it has, as reported by the upload dialog, how many corrugations it has, its dimensions, whether the physics weight or the download weight is higher (More Info link on edit dialog), how you made the physics shape (if you did), and whether it is using smooth shading in Blender. That information would make it easier to give you advice.

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Not as a direct answer to your question, but you can save quite a lot of L.I. by doing some careful texturing and using materials to get the appearance of a corregated surface.  Whether you choose that route or create an actual corregated mesh could depend on factors like (1) how much effect the roof's L.I. will have on the project's total L.I.and (2) how much time people are likely to spend admiring the roof.  Even the nicest roof is only part of the whole building, and it's a part that most people won't spend much time looking at, so it's worth asking how "real" you need to make it look.

If you do decide to make a corregated mesh unit, you can reduce at least some of the L.I. by using a simple rectagular physics shape.  Also by using a simple rectangular shape, appropriately textured, for your lower LOD models.

 

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Drongle McMahon wrote:

Please tell us how many triangles and vertices it has, as reported by the upload dialog, how many corrugations it has, its dimensions, whether the physics weight or the download weight is higher (More Info link on edit dialog), how you made the physics shape (if you did), and whether it is using smooth shading in Blender. That information would make it easier to give you advice.

Hi Drongle,

 

The original plane had 66 corrugations, and I used 2 and 3/4 of the planes. 

The tirangles are 4226 and Verts are 6364 ... A LOT.

I own corrugated iron made by other people with the same/ similar corragations to mine that are only 1 LI and MUCH better smoothness (and no I have not used smoothed shading.) EDIT : Idealy I feel I could get a roof for 6-7LI based on the mesh from others i have seen

So i was really shocked at the LI and T/V count on mine as I have made the roof to sale and the only other things I am importing attached to it are two boxes.

 

Here is my file so you can have a better understanding fo what i'm saying as I am not good with xplaining things.

https://1drv.ms/u/s!AtnNyMcAYHgkqHvJTDgbn7IHBp45

 

Also, I have been using the tried and trusted shading and normal maps however I'm tiring if the flat object look and, whilst no one else may pay much attention. I certainly will. I'm in SL for pretty things and, roofs are included in the land of pretty.

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1) I think the appearance will be better using smooth shading. However, if you do, you have to make the edges sharp using the edge-split modifier*, to avoid shading artifacts in the direction of your corrugations. That will mean there is very little gain of download weight.

2) You have not used at all excessive geometry. The six segments per cycle of the corrugations is the minimum needed for a reasonable appearance when the camera is close.

3) I used half your original panel (i.e.removed the array modifier from the larger object) to do some experiments. I closed off the edge faces at the ends first, then made some lower detail versions. First, dissolving two thirds of the edge loops so that the edge is a zig-zag instead of a smooth curve. Second, dissolving all non-edge edge loops to make a flat panel. Note that with smooth shading and edge split modifiers, both of these look completely flat. The zig-zag just keeps the wavy appearance of the edge where you see its silhouette. To look good, these would have to use at least a normal map to give the corrugated shading. That would only show under advanced lighting. So some otrher faked/baked lighting effect would be needed (as well) to look good under ordinary lighting.

4) Using the panel with default LODs and default physics gave me an LI of 11. The difference between flat and smooth shaded was tiny. Replacing the medium LOD with the zig-zag and the lower two LODs with the flat version gave me an LI of 5. using the flat version for all LODs except high gave an LI of 1. I suspect the latter is what most people would do.

5) None of those LIs is anywhere near the hundreds you mention. You didn't tell us whether it was the download or the physics weight that was high. So I have to guess it was the physics weigh. Using the high LOD for the physics, if I didn't "Analyze", the resulting triangle-based physics shape is less than 0.5m thick. That means it stays as Convex Hull even if you set it to Prim. So this did not give me a high physics weight. The only way I could get a very high physics weight was to use the high LOD mesh and "Analyze". That gave me a physics weight, when set to Prim, of 69. So that's the only thing I can think of that would give you such a high physics weight. This is, of course, completely unnecessary**. The physics can be the flat slab I made for the lowest LOD, weight 0.36. Even using the default convex hull it's only about 0.5. 

*You could get the same effect by using Generate Normals in the upload dialog.

**unless you want realistic rolling on/across the roof corrugations. In that case you will have to pay a lot for physics, even if you use the zig-zag version.

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Hi Drongle, thank you so much for going so in depth for me. I added the edge split modifier and tested botht he smooth and, not smooth shading... In the end because of the pri count. I decided to start from scratch. 

 

After inspecting someone elses mesh roof I realised they had used a pane, that had a face on the top and bottom.

I have created my roof again and they're significantly lower in li... however they only have a face on the top. How do I had a face to the bottom of a pane in blender?

 

cheers.

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In Blender, the default rendering of faces is two-sided. In SL, everything is rendered one-sided. So if you want a top and a bottom, you have to duplicate everything and invert the normals so that the faces point in the opposite direction. To see what's going on in Blender, you can turn on "Backface Culling" in the Shading section of the 3D View's Properties panel. That will make everything one-sided.

There is a quick way to do the duplication by selecting the relevant faces and using Mesh->Faces->Solidify. Or you can use the Solidify modifier, which gives more control, including choosing whether to add edge faces*. With the modifier, you have to define, populate and use a vertex group if you only want part of the mesh solidified, but I think that's not the case with your roof. Anyway, you can always apply thye modifier and then remove any bits you don't want.

*I think that used to be an option with the tool, but it seems to have disappeared (2.77a).

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Drongle McMahon wrote:

 

 Or you can use the Solidify modifier, which gives more control, including choosing whether to add edge faces*.

*I think that used to be an option with the tool, but it seems to have disappeared (2.77a).

    Its still there in 2.77a Drongle, called Fill Rim .

The Only Rim option was added somewhere between 2.71 and 2.73

 



 

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I mean it's not there in the operator panel at the bottom of the tool shelf, after you do Mesh->Faces->Solidify, not the modifier, which has lots of options. I seem to remember it being there before. The tool is easier to use if you only want to solidify a subset of faces, as you don't have to make a vertex group first.

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Hi Guys!

 

Thank you both for your help. I ended up using a solidifier with o thickness and no other options selected. It worked!

I have one question though... The land impact of the larger section is 11. Whilst the section half that size is only 1.something ...

 

Is there a reason for the huge disparity? I am going to be using the half section twice as... there is legit a 10 li difference between the big and small one (only half the size difference)

 

EDIT : also, I can now not bake for some reason. Or more accurately. It's only baking, black. No shadows. I can do it without the solidifier on though. Is this normal?

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Land impact is size dependent.
The larger the object, the less influence the lower LODs will have in contributing to a download weight reduction also.


Interregnums wrote:

EDIT : also, I can now not bake for some reason. Or more accurately. It's only baking, black. No shadows. I can do it without the solidifier on though. Is this normal?

Yes, this is normal, because you have overlapping UVs in the 0 to 1 UV space with solidified geometry. If you want to bake the entire piece, not just one side, you will have to make sure that any UVs have unique space in the 0 to 1 UV space.

Sometimes overlapping UVs are desirable though, to safe texture space (mirrored geometry, repeating detail pieces etc.). In this case the overlapping UV shells have to be moved 1 unit (or 2 or 3 units. Just whole numbers) out of the 0 to 1 UV space for baking. Leaving just one set of UVs in the 0 - 1 space.

 

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