Texture Object Management

cudaError_t cudaCreateTextureObject (cudaTextureObject_t * pTexObject, const struct cudaResourceDesc * pResDesc, const struct cudaTextureDesc * pTexDesc, const struct cudaResourceViewDesc * pResViewDesc)

Creates a texture object and returns it in pTexObject. pResDesc describes the data to texture from. pTexDesc describes how the data should be sampled. pResViewDesc is an optional argument that specifies an alternate format for the data described by pResDesc, and also describes the subresource region to restrict access to when texturing. pResViewDesc can only be specified if the type of resource is a CUDA array or a CUDA mipmapped array.

Texture objects are only supported on devices of compute capability 3.0 or higher. Additionally, a texture object is an opaque value, and, as such, should only be accessed through CUDA API calls.

The cudaResourceDesc structure is defined as:

        struct cudaResourceDesc {
            enum cudaResourceType resType;
            
            union {
                struct {
                    cudaArray_t array;
                } array;
                struct {
                    cudaMipmappedArray_t mipmap;
                } mipmap;
                struct {
                    void *devPtr;
                    struct cudaChannelFormatDesc desc;
                    size_t sizeInBytes;
                } linear;
                struct {
                    void *devPtr;
                    struct cudaChannelFormatDesc desc;
                    size_t width;
                    size_t height;
                    size_t pitchInBytes;
                } pitch2D;
            } res;
        };

where:

• cudaResourceDesc::resType specifies the type of resource to texture from. CUresourceType is defined as:

        enum cudaResourceType {
            cudaResourceTypeArray          = 0x00,
            cudaResourceTypeMipmappedArray = 0x01,
            cudaResourceTypeLinear         = 0x02,
            cudaResourceTypePitch2D        = 0x03
        };

.RS 4 If cudaResourceDesc::resType is set to cudaResourceTypeArray, cudaResourceDesc::res::array::array must be set to a valid CUDA array handle.

.RS 4 If cudaResourceDesc::resType is set to cudaResourceTypeMipmappedArray, cudaResourceDesc::res::mipmap::mipmap must be set to a valid CUDA mipmapped array handle and cudaTextureDesc::normalizedCoords must be set to true.

.RS 4 If cudaResourceDesc::resType is set to cudaResourceTypeLinear, cudaResourceDesc::res::linear::devPtr must be set to a valid device pointer, that is aligned to cudaDeviceProp::textureAlignment. cudaResourceDesc::res::linear::desc describes the format and the number of components per array element. cudaResourceDesc::res::linear::sizeInBytes specifies the size of the array in bytes. The total number of elements in the linear address range cannot exceed cudaDeviceProp::maxTexture1DLinear. The number of elements is computed as (sizeInBytes / sizeof(desc)).

.RS 4 If cudaResourceDesc::resType is set to cudaResourceTypePitch2D, cudaResourceDesc::res::pitch2D::devPtr must be set to a valid device pointer, that is aligned to cudaDeviceProp::textureAlignment. cudaResourceDesc::res::pitch2D::desc describes the format and the number of components per array element. cudaResourceDesc::res::pitch2D::width and cudaResourceDesc::res::pitch2D::height specify the width and height of the array in elements, and cannot exceed cudaDeviceProp::maxTexture2DLinear[0] and cudaDeviceProp::maxTexture2DLinear[1] respectively. cudaResourceDesc::res::pitch2D::pitchInBytes specifies the pitch between two rows in bytes and has to be aligned to cudaDeviceProp::texturePitchAlignment. Pitch cannot exceed cudaDeviceProp::maxTexture2DLinear[2].

The cudaTextureDesc struct is defined as

        struct cudaTextureDesc {
            enum cudaTextureAddressMode addressMode[3];
            enum cudaTextureFilterMode  filterMode;
            enum cudaTextureReadMode    readMode;
            int                         sRGB;
            int                         normalizedCoords;
            unsigned int                maxAnisotropy;
            enum cudaTextureFilterMode  mipmapFilterMode;
            float                       mipmapLevelBias;
            float                       minMipmapLevelClamp;
            float                       maxMipmapLevelClamp;
        };

where

• cudaTextureDesc::addressMode specifies the addressing mode for each dimension of the texture data. cudaTextureAddressMode is defined as:

        enum cudaTextureAddressMode {
            cudaAddressModeWrap   = 0,
            cudaAddressModeClamp  = 1,
            cudaAddressModeMirror = 2,
            cudaAddressModeBorder = 3
        };

This is ignored if cudaResourceDesc::resType is cudaResourceTypeLinear. Also, if cudaTextureDesc::normalizedCoords is set to zero, cudaAddressModeWrap and cudaAddressModeMirror won't be supported and will be switched to cudaAddressModeClamp.

• cudaTextureDesc::filterMode specifies the filtering mode to be used when fetching from the texture. cudaTextureFilterMode is defined as:

        enum cudaTextureFilterMode {
            cudaFilterModePoint  = 0,
            cudaFilterModeLinear = 1
        };

This is ignored if cudaResourceDesc::resType is cudaResourceTypeLinear.

• cudaTextureDesc::readMode specifies whether integer data should be converted to floating point or not. cudaTextureReadMode is defined as:

        enum cudaTextureReadMode {
            cudaReadModeElementType     = 0,
            cudaReadModeNormalizedFloat = 1
        };

Note that this applies only to 8-bit and 16-bit integer formats. 32-bit integer format would not be promoted, regardless of whether or not this cudaTextureDesc::readMode is set cudaReadModeNormalizedFloat is specified.

• cudaTextureDesc::sRGB specifies whether sRGB to linear conversion should be performed during texture fetch.
• cudaTextureDesc::normalizedCoords specifies whether the texture coordinates will be normalized or not.
• cudaTextureDesc::maxAnisotropy specifies the maximum anistropy ratio to be used when doing anisotropic filtering. This value will be clamped to the range [1,16].
• cudaTextureDesc::mipmapFilterMode specifies the filter mode when the calculated mipmap level lies between two defined mipmap levels.
• cudaTextureDesc::mipmapLevelBias specifies the offset to be applied to the calculated mipmap level.
• cudaTextureDesc::minMipmapLevelClamp specifies the lower end of the mipmap level range to clamp access to.
• cudaTextureDesc::maxMipmapLevelClamp specifies the upper end of the mipmap level range to clamp access to.

The cudaResourceViewDesc struct is defined as

        struct cudaResourceViewDesc {
            enum cudaResourceViewFormat format;
            size_t                      width;
            size_t                      height;
            size_t                      depth;
            unsigned int                firstMipmapLevel;
            unsigned int                lastMipmapLevel;
            unsigned int                firstLayer;
            unsigned int                lastLayer;
        };

where:

• cudaResourceViewDesc::format specifies how the data contained in the CUDA array or CUDA mipmapped array should be interpreted. Note that this can incur a change in size of the texture data. If the resource view format is a block compressed format, then the underlying CUDA array or CUDA mipmapped array has to have a 32-bit unsigned integer format with 2 or 4 channels, depending on the block compressed format. For ex., BC1 and BC4 require the underlying CUDA array to have a 32-bit unsigned int with 2 channels. The other BC formats require the underlying resource to have the same 32-bit unsigned int format but with 4 channels.
• cudaResourceViewDesc::width specifies the new width of the texture data. If the resource view format is a block compressed format, this value has to be 4 times the original width of the resource. For non block compressed formats, this value has to be equal to that of the original resource.
• cudaResourceViewDesc::height specifies the new height of the texture data. If the resource view format is a block compressed format, this value has to be 4 times the original height of the resource. For non block compressed formats, this value has to be equal to that of the original resource.
• cudaResourceViewDesc::depth specifies the new depth of the texture data. This value has to be equal to that of the original resource.
• cudaResourceViewDesc::firstMipmapLevel specifies the most detailed mipmap level. This will be the new mipmap level zero. For non-mipmapped resources, this value has to be zero.cudaTextureDesc::minMipmapLevelClamp and cudaTextureDesc::maxMipmapLevelClamp will be relative to this value. For ex., if the firstMipmapLevel is set to 2, and a minMipmapLevelClamp of 1.2 is specified, then the actual minimum mipmap level clamp will be 3.2.
• cudaResourceViewDesc::lastMipmapLevel specifies the least detailed mipmap level. For non-mipmapped resources, this value has to be zero.
• cudaResourceViewDesc::firstLayer specifies the first layer index for layered textures. This will be the new layer zero. For non-layered resources, this value has to be zero.
• cudaResourceViewDesc::lastLayer specifies the last layer index for layered textures. For non-layered resources, this value has to be zero.

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cudaError_t cudaDestroyTextureObject (cudaTextureObject_t texObject)

Destroys the texture object specified by texObject.

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cudaError_t cudaGetTextureObjectResourceDesc (struct cudaResourceDesc * pResDesc, cudaTextureObject_t texObject)

Returns the resource descriptor for the texture object specified by texObject.

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cudaError_t cudaGetTextureObjectResourceViewDesc (struct cudaResourceViewDesc * pResViewDesc, cudaTextureObject_t texObject)

Returns the resource view descriptor for the texture object specified by texObject. If no resource view was specified, cudaErrorInvalidValue is returned.

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cudaError_t cudaGetTextureObjectTextureDesc (struct cudaTextureDesc * pTexDesc, cudaTextureObject_t texObject)

Returns the texture descriptor for the texture object specified by texObject.

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