---
title: BlackPink (Manifold Raymarching Rendering Engine)
author: _"A Blazing 100x100px at 10FPS"_
...
(we had to name it that because Joel likes naming things after pop artists.)
---
# Objective
Can we use raymarching to render primitive objects inside an arbitrary manifold
in real time?
"Non-euclidean rendering" in the most generalised form possible.
---
# Raymarching
- an approximate and fast form of 'raytracing'
- good for primitives (spheres, boxes et cetera.)
- still very expensive
---
# Manifolds
Only one of us does galaxy brain maths.
---
# Tech Stack Requirements
- Fast, compiled code
- We are relatively familiar with it (that disqualifies any _modern_ or "good"
language, and C++)
- Need n-dimensional vectors
- Need to draw pixels on a window
- not Java
---
# C and libSDL2
Its fast (to run) and we "know" it. C is a nice language if only for the
simplicity of its mental model.
libSDL2 is what the big kids like Valve use.
- nicely handles threading, drawing, timers, and gets out of the way.
---
Richal spent 10 hours writing a vector library from scratch.
N-dimentional determinants and cross products _sound_ simple.
---
At one point we were leaking memory at approximately 150Mb per second.
---
---
---
12 Hours later, we could render
- circles
- boxes, and
- straight lines
from one angle, and move them around the scene
- as long as we got lucky with whatever the 4th dimension was doing.
Plus some post-processing and lighting.
---
---
# Results
A 3D renderer where all the maths is done in n-dimensions.
> video
---
# Takeaways 1
- sticking raymarching vectors to manifolds in 4 dimensions is possible but has
a lot of edge cases
---
# Takeaways 2
- having RAII would be really nice when writing a vector library
```c
if (1 || keyboardstate[SDL_SCANCODE_UP]) {
struct ray cameraray = {.pos = copy_vec(camera->pos), .dir = camera->y};
manifoldturn(& cameraray, camera->x, 0);
free_vec(cameraray.pos);
cameraray.pos = copy_vec(camera->pos);
manifoldturn(& cameraray, camera->y, 0);
free_vec(cameraray.pos);
cameraray.pos = camera->pos;
manifoldstep(& cameraray, dist);
free_vec(cameraray.pos);
}
```
