Layer 1 Choosing Memory Type

Classes
struct	VmaMemoryRequirements

Typedefs
typedef enum VmaMemoryUsage	VmaMemoryUsage
typedef struct VmaMemoryRequirements	VmaMemoryRequirements

Enumerations
enum	VmaMemoryUsage {   VMA_MEMORY_USAGE_UNKNOWN = 0, VMA_MEMORY_USAGE_GPU_ONLY = 1, VMA_MEMORY_USAGE_CPU_ONLY = 2, VMA_MEMORY_USAGE_CPU_TO_GPU = 3,   VMA_MEMORY_USAGE_GPU_TO_CPU = 4, VMA_MEMORY_USAGE_MAX_ENUM = 0x7FFFFFFF }

Functions
VkResult	vmaFindMemoryTypeIndex (VmaAllocator allocator, uint32_t memoryTypeBits, const VmaMemoryRequirements *pMemoryRequirements, uint32_t *pMemoryTypeIndex)

Detailed Description

Typedef Documentation

VmaMemoryRequirements

typedef struct VmaMemoryRequirements VmaMemoryRequirements

VmaMemoryUsage

typedef enum VmaMemoryUsage VmaMemoryUsage

Enumeration Type Documentation

VmaMemoryUsage

enum VmaMemoryUsage

Enumerator
VMA_MEMORY_USAGE_UNKNOWN	No intended memory usage specified.
VMA_MEMORY_USAGE_GPU_ONLY	Memory will be used on device only, no need to be mapped on host.
VMA_MEMORY_USAGE_CPU_ONLY	Memory will be mapped on host. Could be used for transfer to device.
VMA_MEMORY_USAGE_CPU_TO_GPU	Memory will be used for frequent (dynamic) updates from host and reads on device.
VMA_MEMORY_USAGE_GPU_TO_CPU	Memory will be used for writing on device and readback on host.
VMA_MEMORY_USAGE_MAX_ENUM

Function Documentation

vmaFindMemoryTypeIndex()

VkResult vmaFindMemoryTypeIndex	(	VmaAllocator	allocator,
		uint32_t	memoryTypeBits,
		const VmaMemoryRequirements *	pMemoryRequirements,
		uint32_t *	pMemoryTypeIndex
	)

This algorithm tries to find a memory type that:

• Is allowed by memoryTypeBits.
• Contains all the flags from pMemoryRequirements->requiredFlags.
• Matches intended usage.
• Has as many flags from pMemoryRequirements->preferredFlags as possible.

Returns

Returns VK_ERROR_FEATURE_NOT_PRESENT if not found. Receiving such result from this function or any other allocating function probably means that your device doesn't support any memory type with requested features for the specific type of resource you want to use it for. Please check parameters of your resource, like image layout (OPTIMAL versus LINEAR) or mip level count.