Bounding Box Issue

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Bounding Box Issue

Post  rufuskins on Mon 25 Jan 2016, 9:40 am

I am currently having problems sorting out the bounding boxes for the 28ft LNWR coaches. These coaches form close coupled sets with all internal coaches having “short” buffers, and the outer brakes having “short” buffers adjacent to internal coaches and “long” buffers at the opposite ends.

Initially I run the the WAG files through Route Riter to determine the centre of gravity and adjust the bounding box. As we know the adjustments in Route Riter are for non UK stock, and hence I then adjust the values in the Size and InertiaTensor lines, as well as the ESD_Bounding_Box in the SD file.

For the typical internal coaches the critical lines in the WAG file are as follows:-

Size ( 2.67m 3.66m 8.86m )

CentreOfGravity ( 0m 1.832m 0.000m )
Mass ( 11.3t )

PassengerCapacity ( 32 )

InertiaTensor ( Box ( 2.67m 3.66m 8.86m ) )


and in the SD file:-

ESD_Bounding_Box ( -1.33 0.9 -4.43 1.33 3.66 4.43 )

For the a brake coach the critical lines in the WAG file are as follows:-

Size ( 2.74m 3.66m 9.22m )

CentreOfGravity ( 0m 1.832m 0.170m )
Mass ( 12.1t )

PassengerCapacity ( 20 )

InertiaTensor ( Box ( 2.74m 3.66m 9.22m ) )


and in the SD file:-

ESD_Bounding_Box ( -1.37 0.9 -4.44 1.37 3.66 4.78 )

However this gives actual gaps as illustrated below:-



The required gap is that shown between the internal coaches but I don't seem to be able to achieve this.

Can anyone please advise a possible solution for which I would be very grateful?


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Re: Bounding Box Issue

Post  MS302 on Mon 25 Jan 2016, 10:54 am

Have you read the tutorial on the Steam4Me site ?

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Re: Bounding Box Issue

Post  ianmacmillan on Mon 25 Jan 2016, 12:02 pm

The gap is controlled by the size not the bounding box.

Did you remember to centre the origin to the over buffer length of the brake rather than the centre of the coach body?

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Re: Bounding Box Issue

Post  rufuskins on Mon 25 Jan 2016, 12:37 pm

ianmacmillan wrote:The gap is controlled by the size not the bounding box.

Did you remember to centre the origin to the over buffer length of the brake rather than the centre of the coach body?

I hadn't realised that that was necessary! Embarassed The buffers are parented to the chassis which is centred to the origin! That means I will need to re-visit all of the 28ft brakes and combine the chassis and buffers parts and use that as the parent centred to the origin. Thank you Ian for another useful lesson.


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Re: Bounding Box Issue

Post  rufuskins on Mon 25 Jan 2016, 2:14 pm

Once more I trudge to the corner picking up the hat labelled with a capital D! Yes you've guessed it I still can't get the perishing thing to locate properly and obviously what I thought needed doing was incorrect! I need to draw breath and try and work it out again, because the answer is probably very simple?


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Re: Bounding Box Issue

Post  rufuskins on Mon 25 Jan 2016, 10:57 pm

rufuskins wrote: . . . because the answer is probably very simple?

I have a feeling that I've just realised what Ian meant, and it confirms my denseness! The following picture illustrates what I believe Ian meant:-



The model was set out based on dimensions based on a datum originating at the centre of the coach, whereas the model should have been set out on dimensions based on a datum originating at a point equidistant from the outer faces of the buffer heads. It would therefore appear that the model parts need to be shifted by the Z dimension in the CentreOf Gravity line; i.e. 170mm. I will therefore amend the models to suit starting tomorrow!


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Re: Bounding Box Issue

Post  ianmacmillan on Tue 26 Jan 2016, 12:03 pm

The model should be moved in TSM.
The certre of gravity method doesn't always work.

I posted instruction once before but can't find the post so I will repeat.
Best copy this to a text file as the search on this site is useless.

Use the ruler in TSM to measure the distance between the buffer faces.
Make a box with that length and add it to the model.
Select all parts. (A key)
Unselect the new box.(Ctrl U)
Drag the selected parts lengthways until they fit in the box.
Unselect all Parts and delete the box.
Select Main and Centre Axis to Origin.

Convert to MSTS and make a consist.
Reduce the size length by a small amount until the gap is correct and make the Bounding Box slightly less to avoid bouncing.

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Re: Bounding Box Issue

Post  rufuskins on Tue 26 Jan 2016, 2:48 pm

Thanks for the guide Ian, and I had ended up doing something similar. I went back into the final TSM model and moved each part 170mm to the left or right depending on which way the brake was facing - this meant that the "z" centre line for the buffers part was at 0.000m! I maintained the parenting as per the original and re-exported to MSTS. I copied the earlier ACE files and ran the revised model through Polymaster and amended the WAG and SD files in line with your suggested method - you had advised me on that at an earlier date. I now need to check the two revised brakes completed so far in MSTS and trust that they are OK?


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