辅导案例-GY 6533 A-Assignment 2

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CS-GY 6533 A Interactive Computer Graphics
Assignment 2: Rasterization
Handout date: 10/03/2019
Submission deadline: 10/24/2019, 23:59 EST
Demo date: 10/25/2019, 9AM-12PM and 1PM-6PM
This homework accounts for 17.5% of your final grade.
Goal of this exercise
In this exercise you will implement a 2D editor for vector graphics. The editor will allow to draw simple
shapes interactively.
Eigen
In all exercises you will need to do operations with vectors and matrices. To simplify the code, you will
use Eigen. Have a look at the “Getting Started” page of Eigen as well as the Quick Reference page
to acquaintain yourselves with the basic matrix operations supported.
OpenGL
In all exercises you will use OpenGL 3.3 with GLSL version 150.
Submission
1. Follow the link sent by assistant to accept assignment and create repository.
2. Modify the code following the assignment instructions
3. Set up Travis-ci badge.
4. Add a report in pdf format that contains what you did with a screenshot for each task
5. Commit and push the code into the repository before the deadline.
1 Mandatory Tasks
For each tasks below, add at least one image in the readme demonstrating the results. The code that
you used for all tasks should be provided.
Claudio Silva and Jonathas Costa - Based on Daniele Panozzo’s Original Notes 1
CS-GY 6533 A Interactive Computer Graphics
1.1 Triangle Soup Editor
Implement an interactive application that allows to add, edit, and delete triangles. The following
operations should be supported:
• The key ’i’ will enable triangle insertion mode. When this mode is enabled, every triple of
subsequent mouse clicks will create a triangle connecting the three locations where the mouse
has been pressed. The first click will create the starting point of the segment, which will be
immediately visualized. As the mouse is moved, a preview of a segment will appear. After the
second mouse click, a preview of the triangle will appear. After the third click, the current preview
will transform into the final triangle.
'i': Triangle insertion mode
Click! Move Click! Move Click!
• The key ’o’ will enable triangle translation mode. Each mouse click will selected the triangle
below the cursor (which will be highlighted), and every movement of the mouse (while keeping
the button pressed) will result in a corresponding translation of the triangle. Note that the triangle
should move on screen by the same amount as the cursor.
'o': Triangle Translation Mode
Move Click!
(keep pressed)
Different color denotes
a selected triangle
Move Move Release mouse
button
• The key ’p’ will enable delete mode. When the mouse is pressed, the triangle below the cursor is
deleted.
1.2 Rotation/Scale
When triangle translation mode is enabled, keep the current primitive selected after the mouse is
released. If a primitive is selected and you press the keys ’h’ and ’j’, the triangle will rotate by 10 degree
Claudio Silva and Jonathas Costa - Based on Daniele Panozzo’s Original Notes 2
CS-GY 6533 A Interactive Computer Graphics
clockwise or counter-clockwise, respectively. The rotations should be done around its barycenter, i.e.
the barycenter of the triangle should not change. When the keys ’k’ or ’l’ are pressed, the primitive
should be scaled up or down by 25%. Similarly to before, the barycenter of the triangle should not move
due to the scaling. For this task, you can directly edit the position of the vertices of the triangles on
the CPU side, and re-upload them to the GPU after every change. If you do it directly in the vertex
shader, you can gain additional points (see Task 1.8)
1.3 Colors
Add the possibility to paint the color of each vertex in the scene. Color mode is enabled by the key
’c’. In this mode, every mouse click will select the vertex closer to the current mouse position. After
a vertex is selected, pressing a key from ’1’ to ’9’ will change its color (the colors that you use are not
important, you can pick whatever colors you like). The color should be interpolated linearly inside the
triangles.
1.4 View Control
Add to the application the capability of changing the camera. The following actions should be supported:
• ’+’ should increase the zoom by 20% zooming in in the center of the screen
• ’-’ should decrease the zoom by 20% zooming out in the center of the screen
• ’w’, ’a’, ’s’, and ’d’ should pan the view by 20% of the visible part of the scene, i.e. translate the
entire scene, respectively down, right, up and left by 20% of the window size.
This should NOT be implemented by changing the coordinates of the objects in the scene. You must
add a view matrix to the vertex shader (as a uniform) that is transforming the position of the vertices of
the triangles before they are rendered. Note that you will also have to transform the screen coordinates
using the inverse of the view matrix, to ensure that the user interaction will adapt to the current view.
'+' '-' 'a'
Claudio Silva and Jonathas Costa - Based on Daniele Panozzo’s Original Notes 3
CS-GY 6533 A Interactive Computer Graphics
1.5 Add keyframing
Add the possibility to keyframe one property of an object (size, position, or rotation) and create an
animation using linear interpolation between the keyframes. You can use a timer to make the animation
automatic, or you could move to the next frame at the press of a button.
Optional Tasks
These tasks are optional. Each one of these tasks is worth 1.5% of the final grade. The optional points
are added to the points of the other exercises, but the total sum of points that you gain with exercises
cannot be more than 80%.
1.6 Additional primitive
Add a new mode that allows to add bezier curves and to move their control points.
1.7 Export in SVG format
Add the possibility to export the current drawing in SVG format https://en.wikipedia.org/wiki/
Scalable_Vector_Graphics. The exported SVG should be compatible with https://inkscape.
org/.
1.8 Shader translation/scaling/rotation
Upload every single triangle as a separate primitive in a separate VBO (or in a single VBO using offsets
for drawing them one by one). For each primitive, upload to the GPU its model matrix (as a uniform)
that transforms the triangle from its canonical position (defined at its creation) to the current position
(obtained by combining translations, scaling and rotations). The transformation should be executed in
the shader, and the content of the VBO storing the vertex positions never updated.
Claudio Silva and Jonathas Costa - Based on Daniele Panozzo’s Original Notes 4
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