Textures

Textures are objects which present images with one, two, or three dimensions, and one or multiple layers. Additionally, they can have multiple mipmap levels, which contain lower resolution variants of the image.

Info

The various objects described on this page are declared in the packages Orka.Rendering.Textures, GL.Objects.Textures and GL.Objects.Samplers.

Creating a texture

A texture can be created by declaring it:

Texture_1 : Texture (GL.Low_Level.Enum.Texture_2D);

After the object has been created, its storage must be allocated:

Texture_1.Allocate_Storage (1, 0, GL.Pixels.RGBA8, Width, Height, 1);

The first parameter specifies the Levels and the second the number of Samples. After storage has been allocated, the texture can be attached to a framebuffer. See Attaching textures for more information on how to attach a texture.

Saving to a KTX file

To save a Texture object to a file, the procedure Write_Texture in the package Orka.Resources.Textures.KTX can be used to write the texture to a .ktx file in a writable location:

Orka.Resources.Textures.KTX.Write_Texture
  (Texture_1, Location_Screenshots, "screenshot.ktx");

The location given to the procedure must implement the interface Writable_Location. See Directories on how to create such an object.

View the saved .ktx file with the orka_ktx tool

The executable orka_ktx of the Alire crate orka_tools can display textures in .ktx files.

Samplers

A sampler specifies how a texture should be sampled. Create a sampler by declaring it:

Sampler_1 : Sampler;

And then modify its state as needed:

Sampler_1.Set_X_Wrapping (Clamp_To_Edge);
Sampler_1.Set_Y_Wrapping (Clamp_To_Edge);

Sampler_1.Set_Minifying_Filter (Linear_Mipmap_Linear);
Sampler_1.Set_Magnifying_Filter (Linear);

Using a sampler in a shader

To use a sampler in a shader, bind it to the index of a binding point:

Sampler_1.Bind (0);

The binding point must be specified in the shader as well:

layout(binding = 0) uniform sampler2D diffuseTexture;

Verify compatibility

To verify that the kind and format of the sampler and texture are compatible, call procedure Verify_Compatibility:

Uniform_1 : Uniform_Sampler := Program_1.Uniform_Sampler ("matrixBuffer");

Uniform_1.Verify_Compatibility (Buffer_Texture_1);