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Polygon manual vector attributes

arno

arno

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Hi,

I have got another problem with reading in SCASM commands for my ModelConverterX tool. In some macros the normal of the polygon (Poly, TexPoly, etc) is defined manually with the "m" argument. That is easy, because then I could just copy it. But these normals also have a length argument. That does not really make sense to me and it seems that the polygon behaves differently if the length is negative. Does anymore remember how this worked? I tried to find some documentation on this, but it is hard to find :).
 
Hello Arno,

All polygons drawing commands had 4 numbers at the start followed by a list of points. The 4 numbers define a plane in the 3D space. VX VY and VZ define a vector or a direction (which is not sufficient to define the plane). The plane is perpendicular to that vector and its distance to the RefPoint is the LEN parameter. So the 4th parameter fixes the plane.

This plane divides the 3D world in 2 1/2 spaces (inner and outer half spaces). For positive LEN the inner 1/2 space is the one that contains the RefPoint.

If the viewpoint is in the outer 1/2 space the polygon is taken (drawn). Otherwise it is skipped.

Negative (!) LEN switchs the meaning of inner and outer.

Scasm had an alternative A parameter. This A replaces the 4 described parameters. The 4 numbers were evaluated from the first 3 points in the list. AI was another alternative whre the LEN taken from the first 3 points was made negative. This was used to draw inside walls, for example.

Hope this is correct and useful.

Kind Regards,

Luis
 
Thanks Luis, I think I fixed it by now. As the vertices of the polygon already define the plane, using only the direction of the normal seemed to work in the end for me. I had some other bugs in my API parser that caused this problems.

The a and ai arguments were a lot easier to implement actually :).
 
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