.3ds import

[Roger H. <rog...@mi...>]

Before my next big project I have been asked to look at .3ds import 
into a 3DMF document.

I compiled up Quesa's 3ds plugin, put it into 3D World and contrary to 
what Peter had told
me, it almost works.

I tried a model of a wooden toy train downloaded from '3DNuts' . By a 
stroke of luck I
happened to choose a model which was not symmetrical. I had to set the 
Mac file type
to 3DMF in Resorcerer, but it read in. There was no colour and some of 
the wheels were
missing, it was a mirror image and it was 'inside out' i.e. a light 
shining from above illuminated
the bottom surface.

Looking at the code I found inside parse3DSChunk in case 
'kChunkVertList' that were three lines
which set the output x to minus the input x, the output y to the input 
z, and the output z to minus
the input y, like this:

					pointList[n].x = -vertex.x;
					pointList[n].y = vertex.z;
					pointList[n].z = -vertex.y;

If I remove the minus sign on the x coordinate I find two of my 
problems disappear, the model
is no longer mirrored and it is no longer inside out so that the sun 
shines on the top of the train.

Should I check in the change? Are there any other corresponding changes 
needed? Does 3DMF
and 3DS use different clockwise/anti-clockwise rule or left hand/right 
hand rule.

Any thoughts on why some of the objects do not appear?

Roger.