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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Rendering Particles Instead of Polygons

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I've spent quite a lot of time perfecting how to draw particles in OpenGL. This is pretty easy, but if you want particles to correspond to world space then things get more difficult. I have found on GitHub other students doing a project with very similar goals to my own project, altough they have executed their project using mainly GPU and Cuda technology. I am doing my code so far a lot on the CPU side so our code will be very different. I did check their shader code for particles, and copied their way of diffusing a particle to get a 3D effect. The clipping needed to make particles appear round did I already discover on other parts of the internet. If interested, this project can be found here . The main issue is that you have to use the shader code "gl_PointSize". This parameter only specifies how many pixels to draw, and don't care about where the pixel is in world space. Luckily someone already asked a question on how to solve this on StackOverflow here . If I ...
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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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