Introduction

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This is going to be my blog for the project part in the course DH2323. I will probably make a project involving collision detection between a shape and an uneven surface, perhaps best described as a set of connected triangles. I have not figured out the details of what I plan to do exactly, but besides solving a general problem statement, I also want to create a program that enables me to demonstrate it properly. I will probably use C++ and GLFW as well as GLM.

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Collisions

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I consider this project to be more or less done now. The last thing I implemented was a way to reduce the amount of collision checks. If one does a naive solution, then all particles gets checked against all particles resulting in a O(n^2) solution. This quickly escalates already for only 3 objects in my expiremts such that it becomes infeasible. So what I did was to read online and most recommended using a 3D uniform grid for the particles. Such that each particle inside a grid voxel was checked only against particles within the voxel itself and adjacent voxels. One powerpoint I found online suggested using a hashmap and only store voxel IDs that are used, otherwise one would have to allocate a huge chunk of memory of a finite amount of space. I could not find that powerpoint again but I'm glad that I remembered this idea. In my solution I ended up using std::map instead which internally has a red-black tree. I used this as it is more reliable, a hash solution can in worst case
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Optimizing Particles With VBO

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I wanted to optimize the way I render particles for an object and also make it have the right dimensions. This was very important to achieve since I will have to do a lot of collision detection later on. I used a VBO to associate one particle-object with a set of particles so that they can be drawn quickly. I spent 24 hours locating a bug that was because I had some deletions in a destructor, which got called automatically in C++ when I copied over an object into an array. One reason for this taking a long time to discover was that there are so many other possible things that can go wrong in OpenGL. I checked the shader code, the initialization for the VBOs and if how I rendered particles on to the screen was wrong. In the end it was neither of these but just a simple destructor error. Here are some cool videos of how the particles looks like for a fox object:
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Particle Generation

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I know there has been a long time since I did any updates, and I am behind my made up schedule for this project. The good news is though that I have managed to create C++ code for generating particles. Given a mesh, which I read from an OBJ-file, I take all the vertices making up the triangles and use these to generate particles on the CPU. I found inspiration for my own solution by the short amount of text described on GPU-Gems 3 chapter 29. GPU-Gems mainly focused on a solution that generated particles with the GPU and Cuda (which only NVIDIA graphics cards can use). Since I am not used to graphics programming, don't have a NVIDIA graphics card on my laptop, and want the code to work on any computer, I decided to generate the particles using normal C++ code. I sort of got stuck on how to generate particles, since I had some bugs in my code. But after discovering and fixing these bugs I got much better result. I know that I haven't explained HOW yet, but here is a short expl
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