Systems and methods for volume rendering

1 . A method for volume rendering, implemented on a computing device having at least one storage device storing a set of instructions, and at least one processor in communication with the at least one storage device, the method comprising:

obtaining, based on volume data, one or more boundary meshes of one or more tissues;

for each ray in a volume rendering operation,

determining one or more intersections of the ray with at least one of the one or more boundary meshes;

determining a tissue label for each of the one or more tissues as visible or invisible in a volume rendering result, each of the one or more boundary meshes having the tissue label of the corresponding tissue; wherein a tissue label of each of the one or more intersections is the same as the tissue label of the boundary mesh corresponding to the intersection;

determining, based on the one or more intersections, target sampling points on the ray, including:

determining, based on the one or more intersections, at least one segment on the ray, each segment being between two adjacent intersections of the one or more intersections, a tissue label of each segment being the same as the tissue label of the intersection corresponding to the segment;

determining a plurality of first sampling points on the at least segment, a tissue label of each first sampling point being the same as the tissue label of the segment where the first sampling point is located; and

determining the target sampling points in the plurality of first sampling points with the tissue labels that are set as visible, wherein the first sampling points with the tissue labels that are set as invisible are not involved in the determining of the brightness of the ray;

determining a brightness of each target sampling point based on one or more rendering parameters corresponding to the target sampling point and a normal of the target sampling point, wherein in response to determining that the target sampling point is adjacent to the one or more boundary meshes, a normal of a mesh patch, intersecting with the ray, of the one or more boundary meshes is used as the normal of the target sampling point; and

determining, based on the brightness of the target sampling points, a volume rendering result of at least one of the one or more tissues.

2 . The method of claim 1 , wherein the obtaining, based on volume data, one or more boundary meshes of one or more tissues includes:

determining the tissue label for each voxel by performing a segmentation operation on the volume data; and

determining, based on the tissue label of the each voxel, a target boundary mesh, among the one or more boundary meshes, of a target tissue.

3 . The method of claim 2 , wherein the determining, based on the tissue label of the each voxel, a target boundary mesh includes:

performing, based on one or more tissue labels of the one or more tissues, a binarization operation on the volume data; and

determining, based on a result of the binarization operation, the target boundary mesh of the target tissue.

4 . The method of claim 3 , wherein the determining, based on a result of the binarization operation, the target boundary mesh of the target tissue includes:

determining, based on at least one of a Marching Cube algorithm, a Simple Marching Cubes algorithm, a Cuberille algorithm, or a Delaunay algorithm, the target boundary mesh of the target tissue.

5 . The method of claim 1 , further comprising:

performing a smoothing operation on the at least one of the one or more boundary meshes.

6 . The method of claim 1 , wherein the at least one of the one or more boundary meshes includes a plurality of mesh patches, and the determining one or more intersections of the ray with at least one of the one or more boundary meshes includes:

traversing the plurality of mesh patches to determine one or more intersections of the ray with the plurality of mesh patches as the one or more intersections of the ray with the at least one of the one or more boundary meshes.

7 . The method of claim 6 , wherein the determining one or more intersections of the ray with at least one of the one or more boundary meshes further includes:

managing, based on a bounding volume hierarchy (BVH) algorithm, the at least one of the one or more boundary meshes.

8 . The method of claim 7 , wherein one or more parent nodes and one or more leaf nodes are configured in the BVH algorithm, each of the one or more parent nodes corresponding to a bounding box, and each of the one or more leaf nodes corresponding to one or more mesh patches of the plurality of mesh patches.

9 . The method of claim 8 , wherein the traversing the plurality of mesh patches includes:

for each parent node of the one or more parent nodes, determining whether the ray intersects with the parent node; and

in response to determining that the ray intersects with the parent node, determining one or more intersections of the ray with one or more leaf nodes corresponding to the parent node as the one or more intersections of the ray with the plurality of mesh patches; or

in response to determining that the ray does not intersect with the parent node, skipping the parent node and the one or more leaf nodes corresponding to the parent node.

10 . The method of claim 1 , wherein the determining, based on the brightness of the target sampling points, a volume rendering result of at least one of the one or more tissues includes:

for the each ray in the volume rendering operation, dividing, based on the one or more intersections, the ray into a plurality of segments;

determining the tissue label of each segment in the plurality of segments; and

generating, based on the tissue label of each segment in the plurality of segments, the volume rendering result of the tissue.

11 . The method of claim 10 , wherein the generating, based on the tissue label of each segment in the plurality of segments, the volume rendering result of the tissue includes:

determining a plurality of sampling points along the ray;

for each sampling point of the plurality of sampling points, determining, based on the tissue label of each segment in the plurality of segments, a tissue label of the sampling point; and

determining, based on the tissue labels of the plurality of sampling points, the volume rendering result of the tissue.

12 . The method of claim 11 , wherein the determining, based on the tissue labels of the plurality of sampling points, the volume rendering result of the tissue includes:

determining whether each of the tissue labels of the plurality of sampling points is visible; and

determining, based on a determination result of whether each of the tissue labels of the plurality of sampling points is visible, the volume rendering result of the tissue.

13 . The method of claim 12 , wherein the determining, based on a determination result of whether each of the tissue labels of the plurality of sampling points is visible, the volume rendering result of the tissue includes:

for each sampling point of the plurality of sampling points,

in response to determining that the tissue label of the sampling point is invisible, skipping a segment where the sampling point is located and proceeding to a next segment;

in response to determining that the tissue label of the sampling point is visible, determining, based on one or more rendering parameters corresponding to the tissue label of the sampling point, a contribution of the sampling point to a brightness of the ray; and

determining, based on a plurality of contributions of the plurality of sampling points, the brightness of the ray.

14 . The method of claim 13 , further comprising:

displaying, based on the brightness of the ray, the volume rendering result of the tissue.

15 . The method of claim 1 , wherein the determining one or more intersections of the ray with at least one of the one or more boundary meshes includes:

constructing a distance field of the at least one of the one or more boundary meshes, for any point in the volume data, the distance field including a shortest distance from the point to the at least one of the one or more boundary meshes; and

determining the one or more intersections of the ray with the at least one of the one or more boundary meshes based on the distance field.

16 . The method of claim 15 , wherein the determining the one or more intersections of the ray with the at least one of the one or more boundary meshes based on the distance field includes:

determining a plurality of points by marching along the ray;

determining a shortest distance from each point of the plurality of points on the ray to the at least one of the one or more boundary meshes based on the distance field;

determining whether the ray intersects the at least one of the one or more boundary meshes based on the shortest distance of each point along the ray; and

in response to determining that the ray intersects the at least one of the one or more boundary meshes, determining the one or more intersections of the ray with the at least one of the one or more boundary meshes.

17 . The method of claim 1 , wherein

the at least one segment is one segment between two intersections, among the one or more intersections, closest to a starting point of the ray; and

the method further comprises:

determining a plurality of second sampling points on a portion of the ray that is out of the segment between the two intersections;

for each second sampling point, determining the tissue label of the tissue corresponding to one or more voxels adjacent to the second sampling point as a tissue label of the second sampling point;

determining the brightness of the ray based on the second sampling points with the tissue labels that are set as visible, wherein the second sampling points with the tissue labels that are set as invisible are not involved in the determining of the brightness of the ray.

18 . A system for volume rendering, comprising:

at least one storage medium including a set of instructions; and

at least one processor in communication with the at least one storage medium, wherein when executing the set of instructions, the at least one processor is directed to cause the system to:

obtain, based on volume data, one or more boundary meshes of one or more tissues;

for each ray in a volume rendering operation,

determine one or more intersections of the ray with at least one of the one or more boundary meshes;

determining a tissue label for each of the one or more tissues as visible or invisible in a volume rendering result, each of the one or more boundary meshes having the tissue label of the corresponding tissue; wherein a tissue label of each of the one or more intersections is the same as the tissue label of the boundary mesh corresponding to the intersection;

determining, based on the one or more intersections, target sampling points on the ray, including:

determining, based on the one or more intersections, at least one segment on the ray, each segment being between two adjacent intersections of the one or more intersections, a tissue label of each segment being the same as the tissue label of the intersection corresponding to the segment;

determining a plurality of first sampling points on the at least segment, a tissue label of each first sampling point being the same as the tissue label of the segment where the first sampling point is located; and

determining the target sampling points in the plurality of first sampling points with the tissue labels that are set as visible wherein the first sampling points with the tissue labels that are set as invisible are not involved in the determining of the brightness of the ray;

determining a brightness of each target sampling point based on one or more rendering parameters corresponding to the target sampling point and a normal of the target sampling point, wherein in response to determining that the target sampling point is adjacent to the one or more boundary meshes, a normal of a mesh patch, intersecting with the ray, of the one or more boundary meshes is used as the normal of the target sampling point; and

determine, based on the brightness of the target sampling points, a volume rendering result of at least one of the one or more tissues.

19 . A non-transitory computer readable medium, comprising executable instructions that, when executed by at least one processor, direct the at least one processor to perform a method for volume rendering, the method comprising:

obtaining, based on volume data, one or more boundary meshes of one or more tissues;

for each ray in a volume rendering operation,

determining one or more intersections of the ray with at least one of the one or more boundary meshes;

determining a tissue label for each of the one or more tissues as visible or invisible in a volume rendering result, each of the one or more boundary meshes having the tissue label of the corresponding tissue; wherein a tissue label of each of the one or more intersections is the same as the tissue label of the boundary mesh corresponding to the intersection;

determining, based on the one or more intersections, target sampling points on the ray, including:

determining, based on the one or more intersections, at least one segment on the ray, each segment being between two adjacent intersections of the one or more intersections, a tissue label of each segment being the same as the tissue label of the intersection corresponding to the segment;

determining a plurality of first sampling points on the at least segment, a tissue label of each first sampling point being the same as the tissue label of the segment where the first sampling point is located; and

determining the target sampling points in the plurality of first sampling points with the tissue labels that are set as visible wherein the first sampling points with the tissue labels that are set as invisible are not involved in the determining of the brightness of the ray;

determining a brightness of each target sampling point based on one or more rendering parameters corresponding to the target sampling point and a normal of the target sampling point, wherein in response to determining that the target sampling point is adjacent to the one or more boundary meshes, a normal of a mesh patch, intersecting with the ray, of the one or more boundary meshes is used as the normal of the target sampling point; and

determining, based on the brightness of the target sampling points, a volume rendering result of at least one of the one or more tissues.