Runtime Texture Atlas was needed when I was creating a blood splatter system for Unity.
A Shadergraph creates a procedural texture saved to a 32×32 CustomRenderTexture.
Next, this small “subtexture” is added to a larger 4096×4096 RenderTexture atlas.
Now 16,384 textures are available for use on the Atlas.
This asset includes 2 methods, Graphics.Blit and Graphics.DrawTexture, with accompanying shaders for each method. The DrawTexture method performs faster because Blit is creating an unnecessary quad during computation. However, depending on the use case, Blit may be desired.
The huge texture that will host a plethora of Subtextures. Example: 4096×4096 RenderTexture.
Subtexture
A smaller image that will be placed into a grid on the AtlasExample: Icons for your game; Procedurally generated CustomRenderTextures such as blood splatters or bullet holes.
An extension of RenderTexture: Pixel data is written by a shader.Procedural shaders / shadergraphs write pixel data to the texture.Not required, but in my case the 32×32 subtextures are generated by a Shadergraph and are rendered to a CustomRenderTexture.https://docs.unity3d.com/ScriptReference/CustomRenderTexture.html
TextureAtlasCreator
A Scriptable Object you will create to configure a runtime texture atlas. Multiple TextureAtlasCreators can be used in your game for various effects, 1 for blood splatters, 1 for bullet holes, 1 for icons, etc.
How To Use
Create a TextureAtlasCreator Scriptable Object by right clicking in your Project Window, Create > Scriptable Objects > Texture Atlas Creator
Add a Rendertexture which will be used for the Atlas or use the default one named: Atlas_RenderTexture_4096x4096.
Configure your Tile Size, or how big each subimage will be.
Select which Graphics API function will be used to copy Pixel Data.
Graphics.DrawTexture is fastest.
Graphics.Blit can also be used depending on your use case.
Call TextureAtlasCreator.AddSubimageToAtlas(Texture subimage)to add a texture to the Atlas.
Call TextureAtlasCreator.AddSubimagesToAtlas(Texture[] subimages)to add an array of textures to the Atlas.
To display a Subimage on a material, you can call TextureAtlasCreator.AssignSubtextureToMaterial(int index, Material material)
For testing purposes, you can assign a texture to “Subimage” and then click “Add Subimage To Atlas” to see how the image is added. Also, click “Flood Subimage To Atlas” to flood the Atlas with the subimage. This allows you to test performance and see what happens when images have to loop back to 0 and previous subimages are overwritten.
Scripts
TextureAtlasCreator.cs
Initialize Atlas
void
InitializeAtlas()
Initialize the Atlas variables. Called automatically from Start() and OnValidate() if in the editor.
Add Subimage To Atlas
int
AddSubimageToAtlas(Texture subimage)
Adds Texture ‘subimage’ to the Atlas. Returns the index of the subimage in the atlas.
Add Subimages To Atlas
int
AddSubimagesToAtlas(Texture[] subimages)
Adds an array of Textures ‘subimages’ to the Atlas. Returns the index of the final subimage.
Assign Subtexture To Material
void
AssignSubtextureToMaterial(int index, Material material)
Given an Atlas Index and a Material, the subtexture at that index will be assigned to the material. Material must have Tiling and Offset parameters.Example: AssignSubtextureToMaterial(AddSubimageToAtlas(subimage), material);
Get Subimage Scale
Vector2
GetSubimageScale(int index)
Returns the scale of the subimage in Vector2. Used by AssignSubtextureToMaterial.
Get Subimage Offset
Vector2
GetSubimageOffset(int index)
Returns the offset of the subimage in Vector2. Used by AssignSubtextureToMaterial.
Clear Atlas RenderTexture
void
ClearAtlasRenderTexture()
Clears the Atlas. All subtextures will be deleted.
AtlasSubtexture.cs
This script is not required and will probably only be used for example purposes. However it may be useful to save a Subtexture’s Index to its Gameobject. For example, a Sword icon is added to the atlas, and the Sword Gameobject has this component added, with a reference to its index in the Atlas. For this case, it’s probably better to just add a “TextureAtlasIndex” variable to your “Sword” class.
Assign Subtexture At Index
void
AssignSubtextureAtIndex(int index)
Find the subtexture which exists at Index in the Texture Atlas and assign it to the GameObject’s material.
