A computer-implemented image processing method comprising: acquiring distribution information of a plurality of physical values of a plurality of types of physical values within a three-dimensional object, the distribution information including respective two-dimensional distributions for each of a plurality of two-dimensional slice surfaces, each two-dimensional slice surface intersecting a predetermined axis through the three-dimensional object at a same angle and at different positions on the predetermined axis in an image processing apparatus; generating, for each of the two-dimensional slice surfaces, a slice image that expresses the respective two-dimensional distribution as an image by determining respective pixel values that includes an alpha value based on a set of the plurality of types of physical values at each position on a respective one of the slice surfaces; and displaying on a display apparatus, as a virtual three-dimensional object, a three-dimensional space that is formed by arranging the slice images at respective corresponding positions on a virtual axis and performing alpha blending drawing according to a position of a viewpoint, wherein the generating includes determining an alpha value at said each position on the slice surfaces, based on the following processs: selecting at least one physical value of the plurality of physical values of a plurality of types of physical values comparing the at least one of said physical values at said each position on the slice surfaces with a predetermined threshold value, and determining, based on the comparison, a provisional alpha value at said each position on the slice surfaces, the provisional alpha value is zero when said at least one physical value is smaller than said threshold value and changes from zero to the threshold level at the threshold value, the threshold level being larger than 1, and determining a final alpha value by multiplying the provisional alpha value with a mathematical function that provides a gradual rise from zero in a provisional alpha value that is smaller than the threshold value by the amount of a predetermined width and further gradually reaches 1 while the provisional alpha value becomes larger than the threshold value by the amount of a predetermined width. acquiring distribution information of a plurality of physical values of a plurality of types of physical values within a three-dimensional object, the distribution information including respective two-dimensional distributions for each of a plurality of two-dimensional slice surfaces, each two-dimensional slice surface intersecting a predetermined axis through the three-dimensional object at a same angle and at different positions on the predetermined axis in an image processing apparatus; generating, for each of the two-dimensional slice surfaces, a slice image that expresses the respective two-dimensional distribution as an image by determining respective pixel values that includes an alpha value based on a set of the plurality of types of physical values at each position on a respective one of the slice surfaces; and displaying on a display apparatus, as a virtual three-dimensional object, a three-dimensional space that is formed by arranging the slice images at respective corresponding positions on a virtual axis and performing alpha blending drawing according to a position of a viewpoint, wherein the generating includes determining an alpha value at said each position on the slice surfaces, based on the following processs: selecting at least one physical value of the plurality of physical values of a plurality of types of physical values comparing the at least one of said physical values at said each position on the slice surfaces with a predetermined threshold value, and determining, based on the comparison, a provisional alpha value at said each position on the slice surfaces, the provisional alpha value is zero when said at least one physical value is smaller than said threshold value and changes from zero to the threshold level at the threshold value, the threshold level being larger than 1, and determining a final alpha value by multiplying the provisional alpha value with a mathematical function that provides a gradual rise from zero in a provisional alpha value that is smaller than the threshold value by the amount of a predetermined width and further gradually reaches 1 while the provisional alpha value becomes larger than the threshold value by the amount of a predetermined width.