cubemap.h

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#pragma once
 
#include <liboscar/graphics/cubemap_face.h>
#include <liboscar/graphics/texture_filter_mode.h>
#include <liboscar/graphics/texture_format.h>
#include <liboscar/graphics/texture_wrap_mode.h>
#include <liboscar/utilities/copy_on_upd_shared_value.h>
 
#include <span>
 
namespace osc
{
    // Represents a single texture composed of six images that are tessellated into
    // a cube shape such that they can be sampled using a direction vector that
    // originates from the center of the cube (i.e. via a `samplerCube`, in GLSL).
    //
    // Note: Each of the six faces of the cube should be provided in the same way
    //       as for a `Texture2D` (i.e. starting in the bottom-left and moving row
    //       by row to the top right), but the direction vector in the GLSL shader
    //       is not in something resembling the texture or world coordinate system.
    //       Instead, it's in a left-handed cube map coordinate system that's used
    //       by shader implementations to figure out which of the six faces to
    //       address with a standard 2D vector in texture coordinate space.
    //
    //       See the OpenGL specification, section 8.13, "Cube Map Texture Selection"
    //       (e.g. https://registry.khronos.org/OpenGL/specs/gl/glspec46.core.pdf) for
    //       more details, but it usually means that the images either have to be
    //       rotated or the direction vector has to be flipped.
    class Cubemap final {
    public:
        // Constructs a cubemap that is `width` physical pixels wide and high, and
        // the given `format`.
        Cubemap(int32_t width, TextureFormat format);
 
        int32_t width() const;
        TextureFormat texture_format() const;
 
        TextureWrapMode wrap_mode() const;  // same as `wrap_mode_u`
        void set_wrap_mode(TextureWrapMode);  // sets all axes
        TextureWrapMode wrap_mode_u() const;
        void set_wrap_mode_u(TextureWrapMode);
        TextureWrapMode wrap_mode_v() const;
        void set_wrap_mode_v(TextureWrapMode);
        TextureWrapMode wrap_mode_w() const;
        void set_wrap_mode_w(TextureWrapMode);
 
        TextureFilterMode filter_mode() const;
        void set_filter_mode(TextureFilterMode);
 
        // The number of provided bytes must match the provided `width*width` and
        // `TextureFormat` of this `Cubemap`, or an exception will be thrown.
        void set_pixel_data(CubemapFace, std::span<const uint8_t>);
 
        friend bool operator==(const Cubemap&, const Cubemap&) = default;
 
        class Impl;
        const Impl& impl() const { return *impl_; }
    private:
        friend class GraphicsBackend;
 
        CopyOnUpdSharedValue<Impl> impl_;
    };
}