The Selection Module

Project Name: MakeHuman

Product Home Page: http://www.makehuman.org/

Code Home Page: https://bitbucket.org/MakeHuman/makehuman/

Authors: Glynn Clements

Copyright(c): MakeHuman Team 2001-2015

Licensing: AGPL3 (http://www.makehuman.org/doc/node/the_makehuman_application.html)

This file is part of MakeHuman (www.makehuman.org).

This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more details.

You should have received a copy of the GNU Affero General Public License along with this program. If not, see <http://www.gnu.org/licenses/>.

Coding Standards: See http://www.makehuman.org/node/165

Abstract

TODO

class selection.SelectionColorMap

The objects support the use of a technique called Selection Using Unique Color IDs, that internally uses color-coding of components within the scene to support the selection of objects by the user using the mouse.

This technique generates a sequence of colors (color IDs), assigning a unique color to each uniquely selectable object or component in the scene. These colors are not displayed, but are used by MakeHuman to generates an unseen image of the various selectable elements. This image uses the same camera settings currently being used for the actual, on-screen image. When the mouse is clicked, the position of the mouse is used with the unseen image to retrieve a color. MakeHuman uses this color as an ID to identify which object or component the user clicked with the mouse.

This technique uses glReadPixels() to read the single pixel at the current mouse location, using the unseen, color-coded image.

For further information on this technique, see:

• http://www.opengl.org/resources/faq/technical/selection.htm and
• http://wiki.gamedev.net/index.php/OpenGL_Selection_Using_Unique_Color_IDs

Note. Because the 3D engine uses glDrawElements in a highly opimized way and each vertex can have only one color ID, there there is a known problem with selecting individual faces with very small FaceGroups using this technique. However, this is not a major problem for MakeHuman, which doesn’t use such low polygon groupings.

• self.colorIDToFaceGroup: Dictionary of colors IDs A dictionary of the color IDs used for selection (see MakeHuman Selectors, above).
• self.colorID: float list A progressive color ID.

The attributes self.colorID and self.colorIDToFaceGroup support a technique called Selection Using Unique Color IDs to make each FaceGroup independently clickable.

The attribute self.colorID stores a progressive color that is incremented for each successive FaceGroup added to the scene. The self.colorIDToFaceGroup attribute contains a list that serves as a directory to map each color back to the corresponding FaceGroup by using its color ID.

assignSelectionID(obj)

This method generates a new, unique color ID for each FaceGroup, within a particular Object3D object, that forms a part of this scene3D object. This color ID can subsequently be used in a non-displayed image map to determine the FaceGroup that a mouse click was made in.

This method loops through the FaceGroups, assigning the next color in the sequence to each subsequent FaceGroup. The color value is written into a ‘dictionary’ to serve as a color ID that can be translated back into the corresponding FaceGroup name when a mouse click is detected. This is part of a technique called Selection Using Unique Color IDs to make each FaceGroup independently clickable.

Parameters:obj (module3d.Object 3D) – The object3D object for which color dictionary entries need to be generated.

getSelectedFaceGroup(picked)

This method uses a non-displayed image containing color-coded faces to return the index of the FaceGroup selected by the user with the mouse. This is part of a technique called Selection Using Unique Color IDs to make each FaceGroup independently clickable.

Returns:The selected face group. Return type:module3d.FaceGroup

getSelectedFaceGroupAndObject(picked)

This method determines whether a FaceGroup or a non-selectable zone has been clicked with the mouse. It returns a tuple, showing the FaceGroup and the parent Object3D object, or None. If no object is picked, this method will simply print “no clickable zone.”

Returns:The selected face group and object. Return type:(module3d.FaceGroup, module3d.Object3d)