Problem Statement

The engine currently has no support for loading cubemap textures. This is a prerequisite for rendering skyboxes and environment-based lighting effects, which are standard features in modern 3D engines.

Proposed Solution

Add a cubemap loading system to the engine that supports:

• Loading six individual face images (right, left, top, bottom, front, back) from disk and assembling them into a cubemap texture.
• Optionally loading cubemaps from a single cross or strip layout image.
• Uploading the cubemap to the GPU as a VkImageViewType::eCube Vulkan image.
• Exposing the cubemap as a usable asset/resource through the engine's resource management system.

Alternative Solutions

• Support only KTX or DDS cubemap formats (single-file, GPU-friendly) — less flexible but avoids manual face assembly.
• Defer cubemap loading to user code and only provide GPU upload utilities — lower scope but forces repetitive user code.

Use Cases

• Use case 1: A developer loads a set of six HDR face images and gets a ready-to-use cubemap texture for environment mapping.
• Use case 2: A skybox renderer (see related issue) uses the cubemap loading system to obtain its texture without handling GPU details directly.
• Use case 3: A future PBR lighting system uses cubemaps for image-based lighting (IBL) probes.

Impact

• New API surface for cubemap asset loading — additive, no breaking changes.
• Requires Vulkan cubemap image creation and upload support.
• No changes to existing rendering paths.

Implementation Details (optional)

• Create a CubemapLoader (or extend the existing texture loader) to handle the six-face assembly.
• Use VK_IMAGE_CREATE_CUBE_COMPATIBLE_BIT and VkImageViewType::eCube for the Vulkan image and image view.
• Integrate with the engine's existing asset/resource system.
• Provide a usage example or test demonstrating a cubemap being loaded and sampled in a shader.

Additional Context

This feature is a prerequisite for the skybox rendering feature.

Related Issues

• [FEAT] Add skybox rendering support #568 (Skybox rendering — depends on this issue)