SYNOPSIS

#include <volpack.h>

vpResult

vpSetCallback(vpc, option, func)

vpContext *vpc;

int option;

void (*func)();

ARGUMENTS

vpc

VolPack context from vpCreateContext.

option

A code specifying which callback function to set.

func

A pointer to the callback function.

DESCRIPTION

vpSetCallback is used to set a callback function. The following list gives the possible values for option:

VP_GRAY_SHADE_FUNC

The func argument is a shading callback function that produces a floating point grayscale pixel intensity. The function should be declared:

void func(void *voxel_ptr, float *i_ptr,
void *client_data);

voxel_ptr

Pointer to the beginning of a voxel that must be shaded.

i_ptr

Location into which the function should store the grayscale intensity result. It should be a single-precision floating point in the range 0.0 (black) to 1.0 (white).

client_data

Pointer to the application-defined client data (see vpSetClientData(3)).

The callback can be used to implement custom shading routines that cannot be implemented with a lookup table. See vpSetLookupShader(3) for more information.

VP_RGB_SHADE_FUNC

The func argument is a shading callback function that produces a floating point RGB pixel intensity. The function should be declared:

void func(void *voxel_ptr, float *r_ptr,
float *r_ptr, float *r_ptr,
void *client_data);

voxel_ptr

Pointer to the beginning of a voxel that must be shaded.

r_ptr, g_ptr, b_ptr

Location into which the function should store the RGB intensities of the result. Each intensity should be a single-precision floating point in the range 0.0 (no intensity) to 1.0 (full intensity).

client_data

Pointer to the application-defined client data (see vpSetClientData(3)).

The callback can be used to implement custom shading routines that cannot be implemented with a lookup table. See vpSetLookupShader(3) for more information.

VP_READ_FUNC

The func argument is a callback function that takes the same arguments and returns the same result as the read(2) system call. This function is used to read data from files (see vpLoadRawVolume(3)). By default, the read system call is used. The callback can be used to implement a custom I/O interface, for example a compression/decompression system.

VP_WRITE_FUNC

The func argument is a callback function that takes the same arguments and returns the same result as the write(2) system call. This function is used to write data to files (see vpStoreRawVolume(3)). By default, the write system call is used. The callback can be used to implement a custom I/O interface, for example a compression/decompression system.

VP_MMAP_FUNC

The func argument is a callback function that is called to memory map data from a file instead of copying the data into memory (see vpLoadRawVolume(3)). The function should be declared:

void *func(int fd, unsigned offset,
void *client_data);

fd

File descriptor from open(2) open for reading.

offset

Byte offset in the file to the beginning of the memory to be mapped.

client_data

Pointer to the application-defined client data (see vpSetClientData(3)).

The function should map the entire file into memory and return a pointer to the memory location that corresponds to the file offset. By default, memory mapping is disabled.

VP_STATUS_FUNC

The func argument is a callback function that is called periodically during long-running operations such as during preprocessing of a volume. The function should be declared:

void func(double frac, void *client_data);

frac

An estimate of the fraction of the current operation that is complete.

client_data

Pointer to the client data associated with the context.

The callback can be used to print a status report or to process time-critical events such as user input. However, the callback should not make any calls to VolPack functions since the internal VolPack state may be inconsistent.

VP_LOG_ALLOC_FUNC

The func argument is a callback function that is called whenever VolPack allocates memory. The function should be declared:

void func(void *ptr, int size, char *use,
int line, char *file, void *client_data);

ptr

Address of the allocated memory.

size

Size (in bytes) of the allocated memory.

use

Short description of the use of the allocated memory.

line

Source code line number for the call to the memory allocator.

file

Source code file name for the call to the memory allocator.

client_data

Pointer to the client data associated with the context.

The callback can be used to track memory allocations (primarily for debugging memory leaks).

VP_LOG_FREE_FUNC

The func argument is a callback function that is called whenever VolPack deallocates memory. The function should be declared:

void func(void *ptr, void *client_data)

ptr

Address of the deallocated memory.

client_data

Pointer to the client data associated with the context.

The callback can be used to track memory deallocations (primarily for debugging memory leaks).

If the func argument is NULL then the corresponding callback function is reset to the default behavior or disabled if there is no default behavior.