Tetra3D
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What is Tetra3D?
Tetra3D is a 3D software renderer written in Go by means of Ebiten, primarily for video games. Compared to a professional 3D rendering systems like OpenGL or Vulkan, it's slow and buggy, but it's also janky, and I love it for that.
It evokes a similar feeling to primitive 3D game consoles like the PS1, N64, or DS. Being that a software renderer is not nearly fast enough for big, modern 3D titles, the best you're going to get out of Tetra is drawing some 3D elements for your primarily 2D Ebiten game, or a relatively rudimentary fully 3D game (maybe something on the level of a PS1 or N64 game would be possible). That said, limitation breeds creativity, and I am intrigued at the thought of what people could make with Tetra.
Why did I make it?
Because there's not really too much of an ability to do 3D for gamedev in Go apart from g3n, go-gl and Raylib-go. I like Go, I like janky 3D, and so, here we are.
It's also interesting to have the ability to spontaneously do things in 3D sometimes. For example, if you were making a 2D game with Ebiten but wanted to display just a few things in 3D, Tetra3D should work well for you.
Finally, while a software renderer is not by any means fast, it is relatively simple and easy to use. Any platforms that Ebiten supports should also work for Tetra3D automatically (hopefully!).
Why Tetra3D? Why is it named that?
Because it's like a tetrahedron, a relatively primitive (but visually interesting) 3D shape made of 4 triangles. Otherwise, I had other names, but I didn't really like them very much. "Jank3D" was the second-best one, haha.
How do you get it?
go get github.com/solarlune/tetra3d
Tetra depends on kvartborg's vector package, takeyourhatoff's bitset package, and Ebiten itself for rendering. Tetra3D requires Go v1.16 or above.
How do you use it?
Make a camera, load a scene, render it. A simple 3D framework means a simple 3D API.
Here's an example:
package main
import (
"errors"
"fmt"
"image/color"
"math"
"os"
"runtime/pprof"
"time"
_ "image/png"
"github.com/solarlune/tetra3d"
"github.com/hajimehoshi/ebiten/v2"
)
const ScreenWidth = 398
const ScreenHeight = 224
type Game struct {
Scene *tetra3d.Scene
Camera *tetra3d.Camera
}
func NewGame() *Game {
g := &Game{}
// First, we load a scene from a .dae file. LoadDAEFile returns a *Scene
// and an error if it was unsuccessful.
scene, err := tetra3d.LoadDAEFile("examples.dae")
if err != nil {
panic(err)
}
g.Scene = scene
// If you need to rotate the model because the 3D modeler you're
// using doesn't use the same axes as Tetra (like Blender),
// you can call Mesh.ApplyMatrix() to apply a rotation matrix
// (or any other kind of matrix) to the vertices, thereby rotating
// them and their triangles' normals.
// By default (if you're using Blender), this conversion is
// done for you; you can change this by passing a different
// DaeLoadOptions parameter when calling tetra3d.LoadDAEFile().
// Tetra uses OpenGL's coordinate system (+X = Right, +Y = Up, +Z = Back),
// in comparison to Blender's coordinate system (+X = Right, +Y = Forward,
// +Z = Up).
// Create a new Camera. We pass the size of the screen to the Camera so
// it can create its own buffer textures (which are *ebiten.Images).
g.Camera = tetra3d.NewCamera(ScreenWidth, ScreenHeight)
// Place Models or Cameras using their Position properties (which is a
// 3D Vector from kvartborg's vector package). Cameras look forward
// down the -Z axis.
g.Camera.Position[2] = 12
return game
}
func (g *Game) Update() error { return nil }
func (g *Game) Draw(screen *ebiten.Image) {
// Call Camera.Clear() to clear its internal backing texture. This
// should be called once per frame before drawing your *Scene.
g.Camera.Clear()
// Now we'll render the Scene from the camera. The Camera's ColorTexture will then
// hold the result.
// We pass both the Scene and the Models because 1) the Scene influences
// how Models draw (fog, for example), and 2) we may not want to render
// all Models. We might want to filter out some Models, which you can do with
// g.Scene.FilterModels().
g.Camera.Render(g.Scene, g.Scene.Models)
// Before drawing the result, clear the screen first.
screen.Fill(color.RGBA{20, 30, 40, 255})
// Draw the resulting texture to the screen, and you're done! You can
// also visualize the depth texture with g.Camera.DepthTexture.
screen.DrawImage(g.Camera.ColorTexture, nil)
}
func (g *Game) Layout(w, h int) (int, int) {
// This is the size of the window; note that a larger (or smaller)
// layout doesn't seem to impact performance very much.
return ScreenWidth, ScreenHeight
}
func main() {
game := NewGame()
if err := ebiten.RunGame(game); err != nil {
panic(err)
}
}
That's basically it. Note that Tetra3D is, indeed, a work-in-progress and so will require time to get to a good state. But I feel like it works pretty well and feels pretty solid to work with as is. Feel free to examine the examples folder for a couple of examples showing how Tetra3D works - simply change to their directory and calling go run . should work.
What's missing?
The following is a rough to-do list (tasks with checks have been implemented):
- 3D rendering
- -- Perspective projection
- -- Orthographic projection
- -- Billboards
- -- Some additional way to draw 2D stuff with no perspective changes (if desired) in 3D space
- -- Basic depth sorting (sorting vertices in a model according to distance, sorting models according to distance)
- -- A depth buffer and depth testing - This is now implemented by means of a depth texture and Kage shader, though the downside is that it requires rendering and compositing the scene into textures twice. Also, it doesn't work on triangles from the same object (as we can't render to the depth texture while reading it for existing depth).
- -- A more advanced depth buffer - currently, the depth is written using vertex colors.
- -- Offscreen Rendering
- -- Model Batching / Combination (Ebiten should batch render calls together automatically, at least partially, as long as we adhere to the efficiency guidelines)
- Culling
- -- Backface culling
- -- Frustum culling
- -- Far triangle culling
- -- Triangle clipping to view (this isn't implemented, but not having it doesn't seem to be too much of a problem for now)
- Debug
- -- Debug text: overall render time, FPS, render call count, vertex count, triangle count, skipped triangle count
- -- Wireframe debug rendering
- -- Normal debug rendering
- Basic Single Image Texturing
- -- Multitexturing?
- -- Materials / Per-triangle images
- -- Perspective-corrected texturing (currently it's affine, see Wikipedia)
- Animations
- -- Armature-based animations
- -- Object transform-based animations
- Scenes
- -- Fog
- -- Ambient vertex coloring
- -- A node or scenegraph for parenting and simple visibility culling
- DAE model loading
- -- Vertex colors loading
- -- UV map loading
- -- Normal loading
- -- Transform / full scene loading
- Lighting?
- Shaders
- -- Normal rendering (useful for, say, screen-space shaders)
- Basic Collisions
- -- AABB collision testing / sphere collision testing?
- -- Raycasting
- Multithreading (particularly for vertex transformations)
- Prefer Discrete GPU for computers with both discrete and integrated graphics cards
Again, it's incomplete and jank. However, it's also pretty cool!
Shout-out time~
Huge shout-out to the open-source community (i.e. StackOverflow, fauxgl, tinyrenderer, learnopengl.com, etc) at large for sharing the information and code to make this possible; I would definitely have never made this happen otherwise.
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