16-889 Assignment 1 Solutions
Rendering Basics with PyTorch3D
Adithya Sampath (Andrew ID: adithyas)
1. Practicing with Cameras
1.1. 360-degree Renders
To get the results run python main.py --question 1.1. The resulting GIF will be stored as images/cow_360.gif
1.2 Re-creating the Dolly Zoom (10 points)
To get the results run python main.py --question 1.2. The resulting GIF will be stored as images/dolly.gif
2. Practicing with Meshes
2.1 Constructing a Tetrahedron (5 points)
To get the results run python main.py --question 2.1. The resulting GIF will be stored as images/tetrahedron.gif
Answer: The tetrahedron should have 4 vertices and 4 faces.
2.2 Constructing a Cube (5 points)
To get the results run python main.py --question 2.2. The resulting GIF will be stored as images/cube.gif
Answer: The cube has 8 vertices and 6 faces. But when we use triangle faces, we have 8 vertices and 12 triangular faces.
3. Re-texturing a mesh (10 points)
To get the results run python main.py --question 3. The resulting GIF will be stored as images/retexture_mesh.gif
Answer: I have chosen, color1 = [0, 0, 1] (Blue) and color2 = [1, 0, 0] (Red)
4. Camera Transformations (20 points)
To get the results run python main.py --question 4.1 or python main.py --question 4.2 or python main.py --question 4.3 or python main.py --question 4.4. The resulting images will be stored in images folder.
| Question | Result | Save path | R_relative | T_relative |
|---|---|---|---|---|
| 4.1 |  |
images/4_1.jpg |
Rotate along Z axis by 90 degrees | No Translation |
| 4.2 |  |
images/4_2.jpg |
No Rotation | Translate along Z axis by 2 meters |
| 4.3 |  |
images/4_3.jpg |
No Rotation | Translate along X axis by 0.5 meters and Y axis by -0.5 meters |
| 4.4 |  |
images/4_4.jpg |
Rotate along Y axis by 90 degrees | Translate -3 meters along X axis and 3 meters along Z axis |
Answer: R_relative applies rotation to the camera and T_relative applies translation to the camera. For both of them we mention how much rotation or translation should be done along each axis.
5. Rendering Generic 3D Representations
5.1 Rendering Point Clouds from RGB-D Images (10 points)
To get the results run python main.py --question 5.1. The resulting GIFs will be stored in images folder.
| Image | Result | Save path |
|---|---|---|
| Point Cloud 1 |  |
images/pot_1.gif |
| Point Cloud 2 |  |
images/pot_2.gif |
| Point Cloud 3 |  |
images/pot_3.gif |
5.2 Parametric Functions (10 points)
To get the results run python main.py --question 5.2. The resulting GIFs will be stored in images folder.
| Number of Points | Result | Save path |
|---|---|---|
| 100 |  |
images/parametric_torus_100.gif |
| 200 |  |
images/parametric_torus_200.gif |
| 1000 |  |
images/parametric_torus_1000.gif |
5.3 Implicit Surfaces (15 points)
To get the results run python main.py --question 5.3. The resulting images will be stored in images folder.
Answer: Rendering a mesh is much faster and less computationally intensive than a point could. The mesh outputs are also of a higher resolution. A mesh takes lesser memory as it only needs to store the parameters of the function. In case of a point cloud, we need to store the coordinates of every point in memory (which is usually very expensive. I got CUDA OUT OF MEMORY errors only for point clouds). With regard to ease of use, it is dependent structure complexity. If it's simple structures, a point cloud may be easier.
6. Do Something Fun (10 points)
To get the results run python main.py --question 6. The resulting GIFs will be stored in the images folder.
| Task | Result | Save path |
|---|---|---|
| Rotate Clockwise |  |
images/charizard_360.gif |
| Rotate Anti-Clockwise |  |
images/charizard_360_2.gif |
| Fly out |  |
images/charizard_fly.gif |
| Fly in |  |
images/charizard_dolly.gif |
Answer: I got the Charizard mesh from Free3D. However the mesh, was oriented in a non-frontal angle (as shown below). Hence, I rotated the mesh by applying rotation and translation matrices to the mesh vertices (similar to what was applied to the camera in Question 4), and recreated the mesh. After rotating the mesh, I created 360 views of the Charizard. For the Charizard flying towards and away from the camera, I applied a modified version of Dolly Zoom.
Fig: Default view of Charizard mesh
(Extra Credit) 7. Sampling Points on Meshes (10 points)
To get the results run python main.py --question 7. The resulting GIFs will be stored in the images folder.
| Number of Points | Result | Save path |
|---|---|---|
| Original |  |
images/cow.gif |
| 10 |  |
images/sample_mesh_points_10.gif |
| 100 |  |
images/sample_mesh_points_100.gif |
| 1000 |  |
images/sample_mesh_points_1000.gif |
| 10000 |  |
images/sample_mesh_points_10000.gif |