Skip to main content

GDC Physics Tutorial

I will give a talk on fluid simulation on GDC this year! Make sure to attend the physics tutorial.

The session will focus on the formulation of a fluid constraint. In contrast to most other particle-based fluid simulatiors, mine uses a sequential impulse solver, normally found in rigid body engines. This improves incompressibility and makes interaction with rigid bodies very stable. This is the method used in Sprinkle and all 3D fluid movies posted earlier on the blog.

The tutorial does also include interesting talks about convex hull creation, physics debugging, constraint solvers and character collision.


Comments

  1. Video of physics classes are good in all manner for us because it dont tak more time of us.

    ReplyDelete
  2. Excellent blog! Please post more :)

    ReplyDelete

Post a Comment

Popular posts from this blog

Bokeh depth of field in a single pass

When I implemented bokeh depth of field I stumbled upon a neat blending trick almost by accident. In my opinion, the quality of depth of field is more related to how objects of different depths blend together, rather than the blur itself. Sure, bokeh is nicer than gaussian, but if the blending is off the whole thing falls flat. There seems to be many different approaches to this out there, most of them requiring multiple passes and sometimes separation of what's behind and in front of the focal plane. I experimented a bit and stumbled upon a nice trick, almost by accident.

I'm not going to get into technical details about lenses, circle of confusion, etc. It has been described very well many times before, so I'm just going to assume you know the basics. I can try to summarize what we want to do in one sentence – render each pixel as a discs where the radius is determined by how out of focus it is, also taking depth into consideration "somehow".

Taking depth into…

Screen Space Path Tracing – Diffuse

The last few posts has been about my new screen space renderer. Apart from a few details I haven't really described how it works, so here we go. I split up the entire pipeline into diffuse and specular light. This post will focusing on diffuse light, which is the hard part.

My method is very similar to SSAO, but instead of doing a number of samples on the hemisphere at a fixed distance, I raymarch every sample against the depth buffer. Note that the depth buffer is not a regular, single value depth buffer, but each pixel contains front and back face depth for the first and second layer of geometry, as described in this post.

The increment for each step is not view dependant, but fixed in world space, otherwise shadows would move with the camera. I start with a small step and then increase the step exponentially until I reach a maximum distance, at which the ray is considered a miss. Needless to say, raymarching multiple samples for every pixel is very costly, and this is without …

Stratified sampling

After finishing my framework overhaul I'm now back on hybrid rendering and screen space raytracing. My first plan was to just port the old renderer to the new framework but I ended up rewriting all of it instead, finally trying out a few things that has been on my mind for a while.

I've been wanting to try stratified sampling for a long time as a way to reduce noise in the diffuse light. The idea is to sample the hemisphere within a certain set of fixed strata instead of completely random to give a more uniform distribution. The direction within each stratum is still random, so it would still cover the whole hemisphere and converge to the same result, just in a slightly more predictable way. I won't go into more detail, but full explanation is all over the Internet, for instance here.

Let's look at the difference between stratified and uniform sampling. To make a fair comparison there is no lighting in these images, just ambient occlusion and an emissive object.


They …