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| /** | |
| * @author Almar Klein / http://almarklein.org | |
| * | |
| * 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. | |
| */ | |
| THREE.VolumeRenderShader1 = { | |
| uniforms: { | |
| "u_size": { value: new THREE.Vector3( 1, 1, 1 ) }, | |
| "u_renderstyle": { value: 0 }, | |
| "u_renderthreshold": { value: 0.5 }, | |
| "u_clim": { value: new THREE.Vector2( 1, 1 ) }, | |
| "u_data": { value: null }, | |
| "u_cmdata": { value: null } | |
| }, | |
| vertexShader: [ | |
| 'varying vec4 v_nearpos;', | |
| 'varying vec4 v_farpos;', | |
| 'varying vec3 v_position;', | |
| 'mat4 inversemat(mat4 m) {', | |
| // Taken from https://github.com/stackgl/glsl-inverse/blob/master/index.glsl | |
| // This function is licenced by the MIT license to Mikola Lysenko | |
| 'float', | |
| 'a00 = m[0][0], a01 = m[0][1], a02 = m[0][2], a03 = m[0][3],', | |
| 'a10 = m[1][0], a11 = m[1][1], a12 = m[1][2], a13 = m[1][3],', | |
| 'a20 = m[2][0], a21 = m[2][1], a22 = m[2][2], a23 = m[2][3],', | |
| 'a30 = m[3][0], a31 = m[3][1], a32 = m[3][2], a33 = m[3][3],', | |
| 'b00 = a00 * a11 - a01 * a10,', | |
| 'b01 = a00 * a12 - a02 * a10,', | |
| 'b02 = a00 * a13 - a03 * a10,', | |
| 'b03 = a01 * a12 - a02 * a11,', | |
| 'b04 = a01 * a13 - a03 * a11,', | |
| 'b05 = a02 * a13 - a03 * a12,', | |
| 'b06 = a20 * a31 - a21 * a30,', | |
| 'b07 = a20 * a32 - a22 * a30,', | |
| 'b08 = a20 * a33 - a23 * a30,', | |
| 'b09 = a21 * a32 - a22 * a31,', | |
| 'b10 = a21 * a33 - a23 * a31,', | |
| 'b11 = a22 * a33 - a23 * a32,', | |
| 'det = b00 * b11 - b01 * b10 + b02 * b09 + b03 * b08 - b04 * b07 + b05 * b06;', | |
| 'return mat4(', | |
| 'a11 * b11 - a12 * b10 + a13 * b09,', | |
| 'a02 * b10 - a01 * b11 - a03 * b09,', | |
| 'a31 * b05 - a32 * b04 + a33 * b03,', | |
| 'a22 * b04 - a21 * b05 - a23 * b03,', | |
| 'a12 * b08 - a10 * b11 - a13 * b07,', | |
| 'a00 * b11 - a02 * b08 + a03 * b07,', | |
| 'a32 * b02 - a30 * b05 - a33 * b01,', | |
| 'a20 * b05 - a22 * b02 + a23 * b01,', | |
| 'a10 * b10 - a11 * b08 + a13 * b06,', | |
| 'a01 * b08 - a00 * b10 - a03 * b06,', | |
| 'a30 * b04 - a31 * b02 + a33 * b00,', | |
| 'a21 * b02 - a20 * b04 - a23 * b00,', | |
| 'a11 * b07 - a10 * b09 - a12 * b06,', | |
| 'a00 * b09 - a01 * b07 + a02 * b06,', | |
| 'a31 * b01 - a30 * b03 - a32 * b00,', | |
| 'a20 * b03 - a21 * b01 + a22 * b00) / det;', | |
| '}', | |
| 'void main() {', | |
| // Prepare transforms to map to "camera view". See also: | |
| // https://threejs.org/docs/#api/renderers/webgl/WebGLProgram | |
| 'mat4 viewtransformf = viewMatrix;', | |
| 'mat4 viewtransformi = inversemat(viewMatrix);', | |
| // 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;', | |
| '}', | |
| ].join( '\n' ), | |
| fragmentShader: [ | |
| '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;', | |
| '}', | |
| ].join( '\n' ) | |
| }; | |