Overview

The overall goal of my final project was to develop a scene around a 3D model that I reconstructed using AgiSoft’s photogrammetry software, PhotoScan Professional 1.2.4. After I scanned in a small cactus atop of a candle box using AgiSoft, I then inserted a fish into the scene and modified the program’s char_callback() so that the user could move the fish around the scene using the keyboard. The keyboard controls for the fish are the following:

The scene also includes a particle system that originates from the fish’s mouth, creating a bubble-like effect. (Please note that I’m aware that fish don’t blow bubbles, it’s just fun to watch). To create an underwater effect, I added in fog to fade the scene into blue the further back the objects are in the scene and added caustic textures to emulate water reflections on the floor of the tank. I animated the caustic texture by rotating through 11 different textures which were set to change based on a specific time interval and used Blinn-Phong to light most of the objects within the scene. The program uses 3 different sets of shaders: one that uses the fog effect, caustics, and optional Blinn-Phong; another that uses the fog effect, caustics, a texture matrix, and Blinn-Phong; and a third that shades a particle system with caustic texturing. In addition to the fog effect and caustic texturing, there’s also collision detection in the scene to add to the reality of the underwater world. By establishing exclusive/inclusive bounds around the cactus and the “tank”, where the fish can swim, the fish is unable to swim through the cactus or swim outside the invisible bounds of the tank.

Caustics (seen on “seafloor”), particle system (from fish’s mouth), 3D reconstructed cactus (center)

Fog effect: Less fog because closer (left), more fog because farther away (right)

Technical Difficulties

My original plan for this project was to use AgiSoft to scan in a coffee mug and construct a scene around that object, but in the process of photographing various mugs and trying to reconstruct models from the images, I realized that I wouldn’t be able to successfully scan in a mug due to its glossy surface. While using the software, I discovered that it works best with more matte colored objects that don’t have a lot of repeating patterns and/or textures on them. Also I came across the problem of the software scanning in a lot of unwanted points, such as the background or foreground of the image. In order to get the best reconstruction that I possibly could, I took well over 300 photos of the cactus from different angles and deleted the background in every photo to ensure that the software would only try to reconstruct the cactus and not any extraneous points picked up from its surroundings. I then went through the dense point cloud of the model and deleted points that were out of place or unnecessary. The whole process of creating the 3D reconstruction was pretty laborious, but with the right backgrounds, cameras, camera angles/alignments, and lighting the process becomes easier and more precise.

One of the initial difficulties I had after I finished reconstructing the cactus was adding a fish object to the scene. The original fish obj file that I wanted to use, required normals to be retrieved separately through an associated normals map. I spent a long while working/debugging a new set of shaders that could handle processing normals using normal maps, and I eventually got it to work. The unfortunate news was that, despite my working shaders, the fish’s lighting still appeared wrong. After a careful look, it was determined that my shaders weren’t the issue, something was wrong with the obj file itself. So I ended up finding a new obj file to use for the fish, but this one didn’t use mapped normals, thus I never ended up using the normal-mapping shaders I had worked on.

Demos:

{click to view video demos}

Demo 1

Demo 2

Links to Concepts

AgiSoft PhotoScan Professional:

http://www.agisoft.com/pdf/PS_1.0.0%20-Tutorial%20(BL)%20-%203D-model.pdf

Caustic Textures:

http://alfonse.bitbucket.org/oldtut/Texturing/Tut17%20Projective%20Texture.html

Fog effect:

http://www.geeks3d.com/20100228/fog-in-glsl-webgl/