texture_get_data doesn't return mipmaps for layered textures

[Xyotic]

Godot version

3.3.2

System information

Windows 10 (ver. 2004), GLES3, NVIDIA GeForce RTX 2080

Issue description

When creating a Texture array with Flag 1 (FlagsEnum.Mipmaps), no mipmaps are created for the layers, nor will existing mipmaps be transfered over.

Since it is possible to set this flag the expected behaviour would be that mipmaps will be created for all layers.

Steps to reproduce

Using C#:

1. Create a TextureArray

TextureArray textureArray = new TextureArray();
textureArray.Create(2048, 2048, 1, Image.Format.Rgba8, (int)TextureLayered.FlagsEnum.Mipmaps);

2. Add Image

textureArray.SetLayerData(myImage, 0);

If in a prior step mipmaps were created they wont get transfered over. ( myImage.GenerateMipmaps() )

3. Check if the Image inside the Texture got any mipmaps

bool hasMipmaps = textureArray.GetLayerData(0).HasMipmaps(); //will be false

Note:
You can also check for mipmaps looking at the size of the Data array of the Image using myImage.GetData().Count() or by checking with .GetMipmapOffset

Minimal reproduction project

No response

[Calinou]

Related to/duplicate of #34312?

[Xyotic]

Seems related...

Also wanted to add:
The documentation states quote: "FLAG_MIPMAPS = 1 --- Texture will generate mipmaps on creation." link
Sounds like the mipmap generation might be already in place, Just happens at the wrong time since you have to call Create() first before adding Images...

[clayjohn]

This was a lot of fun to explore.

The problem in your MRP lies in get_layer_data(). get_layer_data()` calls texture_get_data()`` which is defined here:

godot/drivers/gles3/rasterizer_storage_gles3.cpp

Line 1005 in f3d9314

Ref<Image> RasterizerStorageGLES3::texture_get_data(RID p_texture, int p_layer) const {

texture_get_data() has a different pathway when dealing with layered textures. Unfortunately, it seems that whoever implemented that pathway forget about mipmaps. So texture_get_data() always returns an image without mipmaps when called on a Texture3D or TextureArray. This doesn't mean your image doesn't have mipmaps. The fact that mipmaps are missing from texture_get_data is a bug

You are right to point out that mipmaps are created on texture creation. In your MRP mipmaps are created. However if myImage doesn't have mipmaps, then the mipmaps in textureArray will be ignored when you call setLayerData(), which makes sense, you are only giving Godot a single mip level so it only sets a single mip level. Accordingly, even though you have mipmaps, you are likely never seeing them. This should be better documented.

The combination of these two issues made it look like your TextureArray was never creating mipmaps.

Below is an MRP that shows mipmaps working correctly with TextureArray:

var tex = load("res://icon.png")
var image = tex.get_data() # need to load as a texture otherwise mipmaps are not generated
var textureArray = TextureArray.new()
textureArray.create(64, 64, 1, Image.FORMAT_RGBA8, 1) # allocates space for mipmaps
textureArray.set_layer_data(image, 0)
print(textureArray.data["flags"]) # prints "1" because the mipmap flag is enabled
print(textureArray.get_layer_data(0).has_mipmaps()) # prints "false" because
$ColorRect.material.set_shader_param("tex_array", textureArray)

Shader code for the ColorRect:

shader_type canvas_item;

uniform sampler2DArray tex_array;

void fragment() {
	
	COLOR = textureLod(tex_array, vec3(UV, 0), 3.0*3.0*sin(TIME));
}

[Xyotic]

Thanks for looking into this!
This would have been a mayor performance issue.
I will test your MRP later today.

[Xyotic]

Can confirm this works.

I want to add that:

var image = tex.get_data() # need to load as a texture otherwise mipmaps are not generated

is not 100% correct as you dont need to load it as a texture.
Just call .GenerateMipmaps() on your image before adding it to the array.

This is useful when you dont import your image as a texture