[gpu.resource] resource_write now can have an offset

include/tz/gpu/resource.hpp

@@ -202,7 +202,7 @@ namespace tz::gpu
 	 * 		- If the image was created with @ref image_type::rgba, then each pixel should be 4 bytes - one for each component (0-255).
 	 * 		- If the image was created with @ref image_type::depth or @ref image_type::floats, then each pixel should be 4 bytes - a single signed 32-bit float.
 	 */
-	void resource_write(resource_handle res, std::span<const std::byte> new_data);
+	void resource_write(resource_handle res, std::span<const std::byte> new_data, std::size_t offset = 0);
 	/**
 	 * @ingroup tz_gpu_resource
 	 * @brief Retrieves the current data within a resource.

src/tz/gpu/rhi_vulkan.cpp

@@ -898,12 +898,12 @@ namespace tz::gpu
 		return tz::error_code::success;
 	}
 
-	void resource_write(resource_handle resh, std::span<const std::byte> new_data)
+	void resource_write(resource_handle resh, std::span<const std::byte> new_data, std::size_t offset)
 	{
 		auto& res = resources[resh.peek()];
 		// update the resource data cpu-side.
-		tz_assert(new_data.size_bytes() == res.data.size(), "resource write data span is of wrong size.");
-		std::copy(new_data.begin(), new_data.end(), res.data.begin());
+		tz_assert(offset + new_data.size_bytes() <= res.data.size(), "resource write data span is of wrong size.");
+		std::copy(new_data.begin(), new_data.end(), res.data.begin() + offset);
 		// make sure the change is resident GPU-side.
 		// definitely could cause gpu sync issues if commands are currently in-flight that are reading from it.
 		impl_write_single_resource(resh);