@niivue/niivue/src/utils/webgl-utils.ts

minimal webgl2 nifti image viewer

import { mat4, vec3, vec4 } from 'gl-matrix'

export function swizzleVec3(vec: vec3, order = [0, 1, 2]): vec3 {
    const vout = vec3.create()
    vout[0] = vec[order[0]]
    vout[1] = vec[order[1]]
    vout[2] = vec[order[2]]
    return vout
}

// return boolean is 2D slice view is radiological
// n.b. ambiguous for pure sagittal views
export function isRadiological(mtx: mat4): number {
    const vRight = vec4.fromValues(1, 0, 0, 0) // pure right vector
    const vRotated = vec4.create()
    vec4.transformMat4(vRotated, vRight, mtx)
    return vRotated[0]
}

export function unProject(winX: number, winY: number, winZ: number, mvpMatrix: mat4): vec4 {
    // https://github.com/bringhurst/webgl-unproject
    const inp = vec4.fromValues(winX, winY, winZ, 1.0)
    const finalMatrix = mat4.clone(mvpMatrix)
    // mat.mat4.multiply(finalMatrix, model, proj);
    mat4.invert(finalMatrix, finalMatrix)
    // view is leftTopWidthHeight
    /* Map to range -1 to 1 */
    inp[0] = inp[0] * 2 - 1
    inp[1] = inp[1] * 2 - 1
    inp[2] = inp[2] * 2 - 1
    const out = vec4.create()
    vec4.transformMat4(out, inp, finalMatrix)
    if (out[3] === 0.0) {
        return out
    } // error
    out[0] /= out[3]
    out[1] /= out[3]
    out[2] /= out[3]
    return out
}