Q Solutions

TclOgl Gears Demonstration

Introduction

The purpose of this program is to demonstrate using openGL from within Tcl.
The aim is to demonstrate the following:

Creating an scene and rendering it within openG using a Togl widget.
Displaying multiple Togl Widgets and having seperate drawing contexts for each.
The ease of Texture mapping objects.

Background

The first implementation of a GL interface for Tcl was the Togl widget. This provided a framework for creating custom interfaces in C extensions.

Paule Obermeier modified this code to allow the callbacks from Togl to be made to Tcl procs. Along with the TclOgl interface, it allows GL calls to be made from Tcl.

This provides a near complete interface to the GL API from Tcl.

Operation

The demo provides buttons to create and remove Togl widgets. Each widget will display the Spinning Gears scene.

The Add button will create a new Togl widget with the attributes specified in the entry field and texture menu buttons.

Buttons

Add
Create a new Togl widget and render the spinning gear image into it.
The demo will layout the Togl widgets in a grid of 3x3 as they are created.
Delete
Deletes the last Togl window created.
Update Intercal
Specifies the animation delay between frames for the next Togl window to be created.
Quit
For those people that don't have window managers. Quits the application.

Textures

There is a row of Menu Buttons at the top of the screen, each on is filled in with the names of all loadable images files found in the current directory. Each button corresponds to one gear from largest to smallest. The image None removes the Texture for that gear and renders it in it's base colour.
The menu button specifies the texture for the next Togl widget to be created.

The program scans the current directory for image files. It will use the Img extension if available. The images are turned in Texture vectors that can be assigned to the gears via the Menu buttons at the top of the screen.

Bindings

B1-Motion
Rotate the object within the viewing window.
B2/B3-Motion
Zoom the object.

Credits

Code and inspiration supplied by.

Brian Paul and Ben Bederson for the Mesa GL implementation, the Togl widget, and the original gears C code.
Philip Quaife for the original Togl implementation.
Paul Obermeier for the TclOgl translation
Silicon graphics for the GL standard.

References

* Currently this version does not allow Tcl callback functions, use the version from the TclOgl site.