Hyper Trails

Easy to use and customizable trail effect for the Defold game engine.

Feel free to ask questions: the topic about this asset is on the Defold forum.

Installation

You can use Hyper Trails in your own project by adding this project as a Defold library dependency. Open your game.project file and in the dependencies field under project add:

https://github.com/indiesoftby/defold-hyper-trails/archive/master.zip

Or point to the ZIP file of a specific release.

Usage

Using it in your 2D game is simple:

1. Add .zip as a Defold library dependency - see above.
2. Copy trail_maker.script and trail_model.model from /hyper_trails/hyper_trail_16.go into your game object.
3. Run your game and move the game object. Enjoy!
4. (Optional) Create a custom .texture_profile with Premultiply alpha turned off for the path /hyper_trails/textures/data/ to have a nice preview for trails in the Defold IDE.

Example App

See the demo game.project for examples of how to use Hyper Trails on its own.

🕹️ Play demo online 🕹️

How Does It Work?

1. A 3d model of 15 quads is used, the positions of which are integers: 0,1,2..15.
2. The texture from texture0 sampler is used as an array for a vertex shader.
3. The vertex shader transforms the vertices of this 3d model during rendering of a trail.

Script trail_maker

Properties

⚠️ This doc is a work in progress ⚠️

• use_world_position (boolean) - Calculate object movement delta using go.get_position or go.get_world_position.
• trail_width (number)
• trail_tint_color (vector4)
• segment_length_max (number)
• segment_length_min (number)
• points_count (number) - 16, 32 or 64.
• points_limit (number) - Set 0 to use all points.
• fade_tail_alpha (number)
• shrink_tail_width (boolean)
• shrink_length_per_sec (number)
• texture_tiling (boolean)
• trail_model_url (url)
• auto_update (boolean) - Uncheck this and send the update message to the script instance to manually update the trail.

Model trail_model

The vertex shader transforms the vertices of this 3d model during rendering of a trail.

Hyper Trails comes with three models: with 16, 32 and 64 points (i.e. 15, 31, 63 segments):

• /hyper_trails/models/trail_16.dae (16 points)
• /hyper_trails/models/trail_32.dae (32 points)
• /hyper_trails/models/trail_64.dae (64 points)

Don't forget to set points_count in trail_maker.script according to the selected model.

Properties

• texture0 is a data texture. For each trail in the collection, specify an unique texture0 from /hyper_trails/textures/data/.
• texture1 is drawn on the trail.

FAQ

Why don't you use uniform attributes to render a trail?

1. Defold does not allow you to specify an array as a uniform attribute for the vertex shader.
2. Defold does not allow you to use more than 16 uniform attributes, although the minimum OpenGL ES specs allow is 128 vec4 uniforms in the vertex shader.
3. WebGL and OpenGL ES do not allow you to make an array of these 16 uniform attributes because of this limitation: "Support for indexing array/vector/matrix with a non-constant is only mandated for non-sampler uniforms in the vertex shader".

Known Issues

Data Texture

Each Hyper Trail uses and updates its own instance of data texture. The texture is used as an array for vertex shader. So:

1. Preparing a texture and loading it into GPU memory requires a LOT of CPU time. Keep this in mind when deciding to add 5 or more trails to the collection.
2. Floats encoded in RGBA color with 4 values [0..1]. Due to the low accuracy of these floats, the maximum size of trail is 65535 pixels.
3. For each trail in the collection, specify an unique texture0 for the trail_model.

Trail Position

Defold now has such the update order so a trail head position will always be lagging behind for:

1. Physics-based objects (see the picture below).
2. Objects animated using go.animate().

Tip: use the trail_maker.queue_late_update() function to get rid of this issue. Disable the Auto Update property for the trail maker instance and check the demo/demo_physics.script how to manually send update message to the trail maker script.

Credits

Artsiom Trubchyk (@aglitchman) is the current Hyper Trails owner within Indiesoft and is responsible for the open source repository.

License

MIT License.