3D models losing colors

Jim Canale

I haven't been designing in 3D very long.  And I mostly create models that are homogenous in color.  But today I designed a model consisted of slices of various colors.  The moment I use the UNION command to group the slices, the colors all go to an indeterminate state.  Sometimes the colors on the surface of the object change.  Other times, they all assume the darkest color.  I don't get it.  I realize I can create a block, but I'd like to understand what happens to colors when I use the UNION command.

Scott McKenzie

The union command takes a bunch of solids and creates one solid out of those solids and minimizes the number of coplanar surfaces as it does its thing - generally once a couple of solids are unioned there is no way to un-union them.  Note that there is the separate command used to split a solid apart if there is a gap between the parts of the solid, poor description but the help docs explain it well.  So back to unioning solids, once they have been unioned, they will be rebuilt into one solid representing all of the solids selected, the new solid properties will probably assume those of the first solid selected when starting the union command.

Roy Klein Gebbinck

Scot is correct as far as layer and linetype are concerned. For color the situation is different. If two solids with different colors are joined, edges that were collinear can receive either of the colors. I do not see any underlying logic.

Jim Canale

Thanks to the both of you.    I can see that the purpose of the command is to make one solid and reduce the number of coplanar surfaces.  But like you Roy, I don't see the logic in the selection of the color that takes priority.  

I guess I'm barking up the wrong tree if I intend to retain the colors.  I'll just create blocks.   I was trying to avoid that.  I create a lot of them as it is, and they slow down my work. 

Hans De Backer

The colors of the faces are passed as attributes to the Acis modeling engine, which typically will try to preserve face colors during modifications. In case two or more coplanar faces with different colors are unioned there is no way the engine can know what is 'the right' decision, which color attribute should 'win', so the outcome will be arbitrary. After a union operation in which solids with different colors are involved, often it will be required to manually adjust the color of some of the faces of the new solid.

For your information, the  Selectmodes setting (and toolbar) added in V15, allow to select faces easily. If you want to select faces using a crossing window selection, pressing the Ctrl key after having started the window selection will toggle between selecting Faces, Edges, or complete entities.

It is not clear to me how using blocks can influence or avoid unwanted color changes, an example would be helpful.

Anyway, using blocks is definitely the way to go to speed up work. If e.g. a detailed helical thread is used 100 times in a model, performance for most operations will be much faster if this thread is in a block instead of being modeled separately for every instance. Also file size and memory footprint will be way smaller.

Again it would be helpful to know what you are using blocks for and why they slow you down, it might allow us to give more to the point help.

Louis_Verdonck

 Jim, what about using the GROUP command to keep solids together, while preserving their individual properties? A group can be named and has a 'Selectable' property, which when switched off, allows to edit each member separately.

Jim Canale

 Hans- 

I use a lot of blocks.  Especially in my 2D drawings.   I realize that they speed the placement of duplicates and keep the objects together.    If I explode a block, edit it, and recreate the block, they will ALL be changed.   However, they DO take time to create.  You have to give the block a unique name.   You select the objects, and then you must select the base point.    I have some drawings with 50 or more blocks.  It gets time consuming to scroll down the list to select the block you want to place.  It helps if I add a description.   But that takes time too.

Louis - 

My use of GROUP was similar.  I want the objects to stay together and be selectable.   I just found that in some cases the color of a grouping of multiple colored objects was not predictable.