LibreCAD 3 OpenGL rendering
Librecad ( 2D cad application) can be used for drawing all types for basic shapes on a specified grid area with a very good precision in the position and can be used to draw 2D figures using lines, circles , rectangles, arc’s, etc. Also there are other tools of layers, snap, measure of two points and a command line interface to figure out all the shapes using commands.
Currently rendering of the complete librecad is done using cairo engine. It’s backend does involves some part of opengl but I would like to change the rendering engine and create a complete implementation of OpenGl for the rendering. It would reduce some dependencies of cairo, GTK, etc and another advantages of using OpenGl is it has lower CPU overhead for draw calls which will make the working of Librecad faster.
Right now rendering is done completely using cairo, so my goals will be writing code for the rendering engine in OpenGl ( c/c++ ).
Under the time period of GSoC I would be working on changing the rendering engine which mainly involves the Working Area which contains painter and this will include everything that needs to draw on screen. Also this task will involve with the changes in the part of Command Line Interface tool that creates the image of the result depending on the command entered and for the testing of the engine task will include some unit tests.
Detailed Project Description
- Creating the drawing area with the background and adding grid using horizontal and vertical lines that renders when the program begins and display of the image until any changes are made.
- Implementation of scroll bar (both horizontal and vertical) and set the camera coordinates to fix initial fixed coordinates as the grid is very large to fit in a single screen.
- Adding the feature of zoom in and zoom out to the working area. On zoom, the engine scales the grid and everything on the drawing area with a particular factor and output the scaled image keeping the center according to mouse pointer where zoom is done.
- Creating the mouse pointer with the shape as in the earlier code and display of current coordinates of the mouse pointer. On movement of mouse, continuous rendering occurs and renders the image with pointer at new position and also the display of the coordinates of that position.
- Working of draw tools such as lines, circles, arcs, etc. On select of any of the tool for UI command line interface displays the arguments for the tool. The shape gets created over the grid which displays and highlights the vertices with small squares and highlights the shape when mouse pointer passes through the shape.
- Creating of the select feature. On selecting any point on the working area and dragging the mouse pointer a rectangle gets created of different color and the engine keeps on displaying the rectangle of different area as the mouse moves. If any object happens to lie completely inside the selected area. The particular object gets highlighted along with its reference points. After the release of the mouse, the image of the rectangle dissolves.
- Currently cairo consists of subdirectory cmake which check for the dependencies i.e. cairo, pango, GDK, etc. For the new engine it will check for all dependencies of OpenGl. Also adding part for compiling using opengl in CMakeFiles.txt and further it would give a choice of compiling Librecad using any of the engine according to user.
- Working on unit tests for the testing of rendering by OpenGl. There will be changes in unit tests for rendering and comparing ( with some tolerance ) examples from the resources. Along with this there will be some changes in CMakeFiles.txt because these tests need to be compiled with OpenGl.
Tentative timeline of the project over the summer of 2018.
- Community Bonding Period :
- I will try to complete the research of the previous implementation of the proposed task and also do with the documentation and description of opengl required in my task) and try to get familiar with the working before this period and move on to creation of basic classes in the code.
- I will look at the other implementations of my proposed task and learn about their implementation and get started with it.
- Week 1 (May 14 - May 20) :
- Build a layout for the painter i.e. basic grid and setting camera coordinates at some initial fixed position.
- Also adding scrollbar for horizontal and vertical scrolling up to some extent.
- Week 2 (May 21 - May 27) :
- Creating a mouse pointer of particular shape and making it's movement in sync with the movement of the mouse.
- Dynamic saving and printing of the current coordinates of the mouse.
- Working of the scrollbars and printing of the grid according to the scroll amount.
- Week 3 (May 28 - June 3) :
- Working of the zoom feature and testing of the proper scaling according to the zoom.
- Getting started with the drawing of the cad tools.
- Week 4 (June 4 - June 10) :
- Test my activity and refine it.
- Take more reviews for my work from the mentors.
- Make required changes on the basis of reviews.
- Week 5 (June 11 - June 17) :
- Completing the working of all the basic draw tools.
- Week 6 (June 18 - June 24) :
- Working on the other tools i.e. the dimension tools and also the working of the modify tools.
- Week 7 (June 25 - July 1) :
- Continued working on the implementation of cad tools.
- Testing of the working of draw shapes using command line interface.
- Week 8 (July 2 - July 8) :
- Working of the select feature by click and drag on the area and working on rendering rectangle and related objects.
- Dissolving of the rectangle for selection area on release and highlight of the shape select.
- Week 9 (July 9 - July 15) :
- Continuing the unfinished work of the rectangle and highlight of objects due to it.
- Working of the building of unit tests for the rendering and the comparing the rendered image with the image in the resources.
- Week 10 (July 16 - July 22) :
- Checking tests for different tolerance values and check on the proper working of the tests.
- Week 11 (July 23 - July 29) :
- Working on the choice feature of the CMakeFiles.txt to compile the render according to the user input.
- Week 12 (July 30 - Aug 5) :
- Testing the working on both engines and working of choice feature and **resolving bugs.
Get the changes reviewed from mentors and make the changes accordingly.
I am a second year undergraduate engineering student from International Institute of Information Technology, Hyderabad (IIIT-H), pursuing B.Tech in Electronics and Communication Engineering. I have been contributing to open source projects from the last few months. I love developing games and I have created a few games on Qt and OpenGl.