Adding sprites to atlases at runtime

[appminis-mike]

We support silent updates to our UI, so I need the ability to add a sprite to an atlas at runtime. I've got an image downloaded into a texture, but I'm not sure how to add it to my atlas. I also need the ability to define the borders of a sliced sprite at the time of the import.

What is the best way to achieve this?

[Nicki]

It's not really made to be done at run time.

I suggest you look into how the atlas is made in the first place. Look in UIAtlas.cs and basically anything with Atlas in the name.

You can write pixels to a texture via Texture2D's SetPixels.

[appminis-mike]

Thank you for your response. I have my texture created via PackTextures (which also got me sprite coordinates), and I see how I can add sprites to an atlas, but what's the proper way to assign a texture to a newly created UIAtlas? I've tried setting atlas.spriteMaterial.mainTexture, but that didn't seem to work. Do I need to create a material and a shader first?

What's the right way to get my new texture assigned to an atlas?

[ArenMook]

Create a new material and assign it to the atlas.

[appminis-mike]

I've tried that, but I think I'm doing it wrong. here's what I've got:

1. var testTexture = new Texture2D(1, 1);
2. var coordinates = testTexture.PackTextures(textures.ToArray(), 0);
3.  
4. Material material = new Material(Shader.Find("Diffuse"));
5. material.SetTexture("_MainText", testTexture);
6.  
7. var atlas = GameObject.Find("MyAtlas").GetComponent<UIAtlas>();
8. atlas.spriteMaterial = material;
9.  
10. for(int i = 0; i < coordinates.Count; i++)
11. {
12.         var coordinate = coordinates[i];
13.  
14.         var sprite = new UIAtlas.Sprite();
15.         sprite.name = names[i];
16.         sprite.inner = coordinate;
17.         sprite.outer = coordinate;
18.         atlas.spriteList.Add(sprite);
19.  
20.         atlas.MarkAsDirty();
21. }

Does that look right? I think I'm pretty close.

[ArenMook]

Looks fine to me. Make sure the atlas is using the proper coordinate system. Packed textures are in Tex Coords. Atlas defaults to pixels.

[appminis-mike]

I made this change:

1. var atlas = GameObject.Find("MyAtlas").GetComponent<UIAtlas>();
2. atlas.spriteMaterial = material;
3. atlas.coordinates = UIAtlas.Coordinates.TexCoords;

but I get an error saying:

Can't switch coordinates until the atlas material has a valid texture

Even if I set coordinates after atlas.MarkAsDirty(), I get that error. Also, without the coordinates line, if I click the sprite button on the atlas, it says "The atlas doesn't have a texture to work with", so clearly I'm doing something wrong concerning setting the texture.

[ArenMook]

Well what texture does your material have on it? And what shader is it using?

[appminis-mike]

I'm just using the Diffuse shader, and the texture that I packed with all of my sprites:

1. var testTexture = new Texture2D(1, 1);
2. var coordinates = testTexture.PackTextures(textures.ToArray(), 0);
3.  
4. Material material = new Material(Shader.Find("Diffuse"));
5. material.SetTexture("_MainText", testTexture);

The texture renders okay (and it looks like an atlas texture) if I just print it out to the screen.

[appminis-mike]

Ha, it was right there in front of me:

1. material.SetTexture("_MainText", testTexture);

"_MainText" should have been "_MainTex". The atlas looks good now. Thank you very much for your help!

[bootalmighty]

I am going through this same process to work on adding profile pictures to a game. I can follow all of this assuming we have a texture list that is called textures in this case. What steps would I take to add a texture to an existing atlas, say I have an atlas with preset default pictures and I load up a texture from the web that I want to add? From what is shown it appears as though I need to completely recreate my atlas every time, is this true?