Tuesday, January 31, 2006

OBJ8 - What Not To Use

Here's a short list of some of the features of OBJ8 you should never use:

Don't use ATTR_no_depth. This attribute should probably never have been invented and will be removed someday. There is no situation I can think of in the sim where this attribute is a good idea. (If you do need it, please let me know - tell me why!) Use ATTR_poly_os to put your object on top of a runway or the ground.

Don't use ATTR_ambient_rgb or ATTR_specular_rgb. These attributes are no-ops and have never worked.

Don't use ATTR_diffuse to change the color of your object. Use a small solid-colored patch of your texture - it's much faster. The only reason for ATTR_diffuse is in conjunction with ATTR_emission. I will explain this special usage in another post.

Don't use ATTR_shade_flat. You can represent any shading, smooth or flat, with ATTR_shade_smooth. In AC3D this means clicking the 'smooth' button and using the crease-angle to create the appropriate look for your object.

Don't use ATTR_poly_os with huge offsets. Even if you stack several layers of offset polygons on top of each other, you do not need to make each offset larger and larger; the offset only needs to be large enough to put the polygon over the base terrain. An offset of 1 or 2 is almost always adequate.

A few other warnings: Don't rely on your objects being drawn in a certain order in the sim - this will change! Don't put lights in the middle of your objects - when textured they will only look right at the end of the object.

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