290 lines
9.5 KiB
JavaScript
290 lines
9.5 KiB
JavaScript
|
import {
|
||
|
|
Vector2,
|
||
|
|
Vector3
|
||
|
|
} from 'three';
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Shaders to render 3D volumes using raycasting.
|
||
|
|
* The applied techniques are based on similar implementations in the Visvis and Vispy projects.
|
||
|
|
* This is not the only approach, therefore it's marked 1.
|
||
|
|
*/
|
||
|
|
|
||
|
|
const VolumeRenderShader1 = {
|
||
|
|
|
||
|
|
uniforms: {
|
||
|
|
'u_size': { value: new Vector3( 1, 1, 1 ) },
|
||
|
|
'u_renderstyle': { value: 0 },
|
||
|
|
'u_renderthreshold': { value: 0.5 },
|
||
|
|
'u_clim': { value: new Vector2( 1, 1 ) },
|
||
|
|
'u_data': { value: null },
|
||
|
|
'u_cmdata': { value: null }
|
||
|
|
},
|
||
|
|
|
||
|
|
vertexShader: /* glsl */`
|
||
|
|
|
||
|
|
varying vec4 v_nearpos;
|
||
|
|
varying vec4 v_farpos;
|
||
|
|
varying vec3 v_position;
|
||
|
|
|
||
|
|
void main() {
|
||
|
|
// Prepare transforms to map to "camera view". See also:
|
||
|
|
// https://threejs.org/docs/#api/renderers/webgl/WebGLProgram
|
||
|
|
mat4 viewtransformf = modelViewMatrix;
|
||
|
|
mat4 viewtransformi = inverse(modelViewMatrix);
|
||
|
|
|
||
|
|
// Project local vertex coordinate to camera position. Then do a step
|
||
|
|
// backward (in cam coords) to the near clipping plane, and project back. Do
|
||
|
|
// the same for the far clipping plane. This gives us all the information we
|
||
|
|
// need to calculate the ray and truncate it to the viewing cone.
|
||
|
|
vec4 position4 = vec4(position, 1.0);
|
||
|
|
vec4 pos_in_cam = viewtransformf * position4;
|
||
|
|
|
||
|
|
// Intersection of ray and near clipping plane (z = -1 in clip coords)
|
||
|
|
pos_in_cam.z = -pos_in_cam.w;
|
||
|
|
v_nearpos = viewtransformi * pos_in_cam;
|
||
|
|
|
||
|
|
// Intersection of ray and far clipping plane (z = +1 in clip coords)
|
||
|
|
pos_in_cam.z = pos_in_cam.w;
|
||
|
|
v_farpos = viewtransformi * pos_in_cam;
|
||
|
|
|
||
|
|
// Set varyings and output pos
|
||
|
|
v_position = position;
|
||
|
|
gl_Position = projectionMatrix * viewMatrix * modelMatrix * position4;
|
||
|
|
}`,
|
||
|
|
|
||
|
|
fragmentShader: /* glsl */`
|
||
|
|
|
||
|
|
precision highp float;
|
||
|
|
precision mediump sampler3D;
|
||
|
|
|
||
|
|
uniform vec3 u_size;
|
||
|
|
uniform int u_renderstyle;
|
||
|
|
uniform float u_renderthreshold;
|
||
|
|
uniform vec2 u_clim;
|
||
|
|
|
||
|
|
uniform sampler3D u_data;
|
||
|
|
uniform sampler2D u_cmdata;
|
||
|
|
|
||
|
|
varying vec3 v_position;
|
||
|
|
varying vec4 v_nearpos;
|
||
|
|
varying vec4 v_farpos;
|
||
|
|
|
||
|
|
// The maximum distance through our rendering volume is sqrt(3).
|
||
|
|
const int MAX_STEPS = 887; // 887 for 512^3, 1774 for 1024^3
|
||
|
|
const int REFINEMENT_STEPS = 4;
|
||
|
|
const float relative_step_size = 1.0;
|
||
|
|
const vec4 ambient_color = vec4(0.2, 0.4, 0.2, 1.0);
|
||
|
|
const vec4 diffuse_color = vec4(0.8, 0.2, 0.2, 1.0);
|
||
|
|
const vec4 specular_color = vec4(1.0, 1.0, 1.0, 1.0);
|
||
|
|
const float shininess = 40.0;
|
||
|
|
|
||
|
|
void cast_mip(vec3 start_loc, vec3 step, int nsteps, vec3 view_ray);
|
||
|
|
void cast_iso(vec3 start_loc, vec3 step, int nsteps, vec3 view_ray);
|
||
|
|
|
||
|
|
float sample1(vec3 texcoords);
|
||
|
|
vec4 apply_colormap(float val);
|
||
|
|
vec4 add_lighting(float val, vec3 loc, vec3 step, vec3 view_ray);
|
||
|
|
|
||
|
|
|
||
|
|
void main() {
|
||
|
|
// Normalize clipping plane info
|
||
|
|
vec3 farpos = v_farpos.xyz / v_farpos.w;
|
||
|
|
vec3 nearpos = v_nearpos.xyz / v_nearpos.w;
|
||
|
|
|
||
|
|
// Calculate unit vector pointing in the view direction through this fragment.
|
||
|
|
vec3 view_ray = normalize(nearpos.xyz - farpos.xyz);
|
||
|
|
|
||
|
|
// Compute the (negative) distance to the front surface or near clipping plane.
|
||
|
|
// v_position is the back face of the cuboid, so the initial distance calculated in the dot
|
||
|
|
// product below is the distance from near clip plane to the back of the cuboid
|
||
|
|
float distance = dot(nearpos - v_position, view_ray);
|
||
|
|
distance = max(distance, min((-0.5 - v_position.x) / view_ray.x,
|
||
|
|
(u_size.x - 0.5 - v_position.x) / view_ray.x));
|
||
|
|
distance = max(distance, min((-0.5 - v_position.y) / view_ray.y,
|
||
|
|
(u_size.y - 0.5 - v_position.y) / view_ray.y));
|
||
|
|
distance = max(distance, min((-0.5 - v_position.z) / view_ray.z,
|
||
|
|
(u_size.z - 0.5 - v_position.z) / view_ray.z));
|
||
|
|
|
||
|
|
// Now we have the starting position on the front surface
|
||
|
|
vec3 front = v_position + view_ray * distance;
|
||
|
|
|
||
|
|
// Decide how many steps to take
|
||
|
|
int nsteps = int(-distance / relative_step_size + 0.5);
|
||
|
|
if ( nsteps < 1 )
|
||
|
|
discard;
|
||
|
|
|
||
|
|
// Get starting location and step vector in texture coordinates
|
||
|
|
vec3 step = ((v_position - front) / u_size) / float(nsteps);
|
||
|
|
vec3 start_loc = front / u_size;
|
||
|
|
|
||
|
|
// For testing: show the number of steps. This helps to establish
|
||
|
|
// whether the rays are correctly oriented
|
||
|
|
//'gl_FragColor = vec4(0.0, float(nsteps) / 1.0 / u_size.x, 1.0, 1.0);
|
||
|
|
//'return;
|
||
|
|
|
||
|
|
if (u_renderstyle == 0)
|
||
|
|
cast_mip(start_loc, step, nsteps, view_ray);
|
||
|
|
else if (u_renderstyle == 1)
|
||
|
|
cast_iso(start_loc, step, nsteps, view_ray);
|
||
|
|
|
||
|
|
if (gl_FragColor.a < 0.05)
|
||
|
|
discard;
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
float sample1(vec3 texcoords) {
|
||
|
|
/* Sample float value from a 3D texture. Assumes intensity data. */
|
||
|
|
return texture(u_data, texcoords.xyz).r;
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
vec4 apply_colormap(float val) {
|
||
|
|
val = (val - u_clim[0]) / (u_clim[1] - u_clim[0]);
|
||
|
|
return texture2D(u_cmdata, vec2(val, 0.5));
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
void cast_mip(vec3 start_loc, vec3 step, int nsteps, vec3 view_ray) {
|
||
|
|
|
||
|
|
float max_val = -1e6;
|
||
|
|
int max_i = 100;
|
||
|
|
vec3 loc = start_loc;
|
||
|
|
|
||
|
|
// Enter the raycasting loop. In WebGL 1 the loop index cannot be compared with
|
||
|
|
// non-constant expression. So we use a hard-coded max, and an additional condition
|
||
|
|
// inside the loop.
|
||
|
|
for (int iter=0; iter<MAX_STEPS; iter++) {
|
||
|
|
if (iter >= nsteps)
|
||
|
|
break;
|
||
|
|
// Sample from the 3D texture
|
||
|
|
float val = sample1(loc);
|
||
|
|
// Apply MIP operation
|
||
|
|
if (val > max_val) {
|
||
|
|
max_val = val;
|
||
|
|
max_i = iter;
|
||
|
|
}
|
||
|
|
// Advance location deeper into the volume
|
||
|
|
loc += step;
|
||
|
|
}
|
||
|
|
|
||
|
|
// Refine location, gives crispier images
|
||
|
|
vec3 iloc = start_loc + step * (float(max_i) - 0.5);
|
||
|
|
vec3 istep = step / float(REFINEMENT_STEPS);
|
||
|
|
for (int i=0; i<REFINEMENT_STEPS; i++) {
|
||
|
|
max_val = max(max_val, sample1(iloc));
|
||
|
|
iloc += istep;
|
||
|
|
}
|
||
|
|
|
||
|
|
// Resolve final color
|
||
|
|
gl_FragColor = apply_colormap(max_val);
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
void cast_iso(vec3 start_loc, vec3 step, int nsteps, vec3 view_ray) {
|
||
|
|
|
||
|
|
gl_FragColor = vec4(0.0); // init transparent
|
||
|
|
vec4 color3 = vec4(0.0); // final color
|
||
|
|
vec3 dstep = 1.5 / u_size; // step to sample derivative
|
||
|
|
vec3 loc = start_loc;
|
||
|
|
|
||
|
|
float low_threshold = u_renderthreshold - 0.02 * (u_clim[1] - u_clim[0]);
|
||
|
|
|
||
|
|
// Enter the raycasting loop. In WebGL 1 the loop index cannot be compared with
|
||
|
|
// non-constant expression. So we use a hard-coded max, and an additional condition
|
||
|
|
// inside the loop.
|
||
|
|
for (int iter=0; iter<MAX_STEPS; iter++) {
|
||
|
|
if (iter >= nsteps)
|
||
|
|
break;
|
||
|
|
|
||
|
|
// Sample from the 3D texture
|
||
|
|
float val = sample1(loc);
|
||
|
|
|
||
|
|
if (val > low_threshold) {
|
||
|
|
// Take the last interval in smaller steps
|
||
|
|
vec3 iloc = loc - 0.5 * step;
|
||
|
|
vec3 istep = step / float(REFINEMENT_STEPS);
|
||
|
|
for (int i=0; i<REFINEMENT_STEPS; i++) {
|
||
|
|
val = sample1(iloc);
|
||
|
|
if (val > u_renderthreshold) {
|
||
|
|
gl_FragColor = add_lighting(val, iloc, dstep, view_ray);
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
iloc += istep;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// Advance location deeper into the volume
|
||
|
|
loc += step;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
vec4 add_lighting(float val, vec3 loc, vec3 step, vec3 view_ray)
|
||
|
|
{
|
||
|
|
// Calculate color by incorporating lighting
|
||
|
|
|
||
|
|
// View direction
|
||
|
|
vec3 V = normalize(view_ray);
|
||
|
|
|
||
|
|
// calculate normal vector from gradient
|
||
|
|
vec3 N;
|
||
|
|
float val1, val2;
|
||
|
|
val1 = sample1(loc + vec3(-step[0], 0.0, 0.0));
|
||
|
|
val2 = sample1(loc + vec3(+step[0], 0.0, 0.0));
|
||
|
|
N[0] = val1 - val2;
|
||
|
|
val = max(max(val1, val2), val);
|
||
|
|
val1 = sample1(loc + vec3(0.0, -step[1], 0.0));
|
||
|
|
val2 = sample1(loc + vec3(0.0, +step[1], 0.0));
|
||
|
|
N[1] = val1 - val2;
|
||
|
|
val = max(max(val1, val2), val);
|
||
|
|
val1 = sample1(loc + vec3(0.0, 0.0, -step[2]));
|
||
|
|
val2 = sample1(loc + vec3(0.0, 0.0, +step[2]));
|
||
|
|
N[2] = val1 - val2;
|
||
|
|
val = max(max(val1, val2), val);
|
||
|
|
|
||
|
|
float gm = length(N); // gradient magnitude
|
||
|
|
N = normalize(N);
|
||
|
|
|
||
|
|
// Flip normal so it points towards viewer
|
||
|
|
float Nselect = float(dot(N, V) > 0.0);
|
||
|
|
N = (2.0 * Nselect - 1.0) * N; // == Nselect * N - (1.0-Nselect)*N;
|
||
|
|
|
||
|
|
// Init colors
|
||
|
|
vec4 ambient_color = vec4(0.0, 0.0, 0.0, 0.0);
|
||
|
|
vec4 diffuse_color = vec4(0.0, 0.0, 0.0, 0.0);
|
||
|
|
vec4 specular_color = vec4(0.0, 0.0, 0.0, 0.0);
|
||
|
|
|
||
|
|
// note: could allow multiple lights
|
||
|
|
for (int i=0; i<1; i++)
|
||
|
|
{
|
||
|
|
// Get light direction (make sure to prevent zero devision)
|
||
|
|
vec3 L = normalize(view_ray); //lightDirs[i];
|
||
|
|
float lightEnabled = float( length(L) > 0.0 );
|
||
|
|
L = normalize(L + (1.0 - lightEnabled));
|
||
|
|
|
||
|
|
// Calculate lighting properties
|
||
|
|
float lambertTerm = clamp(dot(N, L), 0.0, 1.0);
|
||
|
|
vec3 H = normalize(L+V); // Halfway vector
|
||
|
|
float specularTerm = pow(max(dot(H, N), 0.0), shininess);
|
||
|
|
|
||
|
|
// Calculate mask
|
||
|
|
float mask1 = lightEnabled;
|
||
|
|
|
||
|
|
// Calculate colors
|
||
|
|
ambient_color += mask1 * ambient_color; // * gl_LightSource[i].ambient;
|
||
|
|
diffuse_color += mask1 * lambertTerm;
|
||
|
|
specular_color += mask1 * specularTerm * specular_color;
|
||
|
|
}
|
||
|
|
|
||
|
|
// Calculate final color by componing different components
|
||
|
|
vec4 final_color;
|
||
|
|
vec4 color = apply_colormap(val);
|
||
|
|
final_color = color * (ambient_color + diffuse_color) + specular_color;
|
||
|
|
final_color.a = color.a;
|
||
|
|
return final_color;
|
||
|
|
}`
|
||
|
|
|
||
|
|
};
|
||
|
|
|
||
|
|
export { VolumeRenderShader1 };
|