无障碍模式下如何实现轨迹球定位的辅助功能
在现代社会中，推动无障碍设计已经成为一项重要的任务。为保障视力、听力或肢体上的缺陷人员能够更加舒适地使用网络，我们需要考虑设计并开发一些有益于辅助功能的特性。其中，轨迹球定位技术就是这样一种便捷的技术，它能够为这些人群提供更好的浏览体验。
什么是轨迹球定位
轨迹球定位是一种以鼠标滚轮控制的定位技术，它常常被用于CAD设计和3D建模等领域。用户可以通过操作轨迹球来对物体进行部署和旋转操作。与其他鼠标和键盘操作相比，它可以更加准确和快速地操作。
使用初衷
虽然轨迹球定位技术主要是为了在CAD设计和3D建模等领域中使用，但它的使用范围已经逐渐扩大到了其它领域。例如，现代游戏中，很多游戏也采用了类似的技术。虽然原始技术是为了更舒适地进行长时间CAD设计工作所设计的，但轨迹球也被应用到了其它一些方面。
轨迹球定位的无障碍实现
对于视力、听力或肢体上的缺陷人员而言，轨迹球定位技术是一种非常有用的工具。然而，对于一些残障人士而言，使用轨迹球定位技术可能会产生一些困难。为了解决这些难题，我们需要考虑轨迹球定位的无障碍实现。
增大轨迹球的目标区域
如果轨迹球的控制区域过小，那么使用者的肢体缺陷可能会导致无法完全控制轨迹球。因此，在实现轨迹球定位技术时，我们可以增大控制区域，以便将其能够更方便地使用。
改变鼠标的行为
对于残障人士而言，将鼠标的行为调整到最适合他们的程度是非常重要的。因此，我们可以通过在鼠标滚轮上加入额外的控制，来定制使用者需要的滚动行为。
使用轨迹球来控制页面的缩放
轨迹球通常用来控制物体的位置和旋转。但是尝试将它用在浏览器中，可以达到惊人的效果。比如，你可以通过轨迹球缩放网页，来适应自己的视力或缺失部位。
示例代码
HTML 代码
<canvas></canvas>
JavaScript 代码
var canvas = document.querySelector('canvas');
var gl = canvas.getContext('webgl');
var geometry = new THREE.IcosahedronGeometry(5, 0);
var material = new THREE.MeshPhongMaterial({color: 0xffffff, flatShading: true, vertexColors: THREE.FlatShading});
for (var i = 0; i < geometry.faces.length; i ++) {
face = geometry.faces[i];
face.vertexColors[0] = new THREE.Color().setRGB(1.0, 0.8, 0.8);
face.vertexColors[1] = new THREE.Color().setRGB(0.8, 1.0, 0.8);
face.vertexColors[2] = new THREE.Color().setRGB(0.8, 0.8, 1.0);
}
var lighting = function() {
this.ambientLightColor = 0x000000;
this.pointLightColor = 0xffffff;
this.intensity = 500000;
this.distance = 0;
this.angle = 0.4;
this.x = 0;
this.y = 0;
this.z = 0;
this.exponent = 5;
};
var boundingSphere = new THREE.Sphere();
boundingSphere.setFromPoints(geometry.vertices);
var bias = Math.max(0, boundingSphere.radius - Math.sqrt(boundingSphere.radius));
boundingSphere.radius += bias;
var vertexShader = "\n varying vec3 vNormal;\n varying vec3 vViewPosition;\n void main() {\n vNormal = normal;\n vViewPosition = -position;\n gl_Position = projectionMatrix * modelViewMatrix * vec4(position, 1.0);\n }";
var fragmentShader = "\n uniform vec3 pointLightColor;\n uniform float pointLightCastShadow;\n varying vec3 vNormal;\n varying vec3 vViewPosition;\n uniform vec3 ambientLightColor;\n uniform float opacity;\n\n float specularStrength = 1.5;\n float shininess = 200.0;\n\n float computeShadow(in vec4 lightSpacePosition, in int frontFacing, in float bias, in float mapSize, in sampler2D shadowMap) {\n vec3 projCoords = lightSpacePosition.xyz/lightSpacePosition.w;\n projCoords = projCoords * 0.5 + 0.5;\n if (projCoords.z > 1.0) {\n return 0.0;\n }\n float neardistance = length(vViewPosition) + bias;\n\n float fardistance = neardistance + mapSize;\n\n float pcfRadius = 1.0;\n\n float shadow = 0.0;\n if (pointLightCastShadow != 0.0) {\n for (int i = -2; i <= 2; i ++) {\n for (int j = -2; j <= 2; j ++) {\n float offsetsx = float(i);\n float offsetsy = float(j);\n vec4 offsets = vec4(offsetsx,offsetsy,0,0);\n vec4 texCoords = vec4(projCoords.xy, projCoords.z, 1);\n if (frontFacing == 1) {\n shadow += texture2D(shadowMap, texCoords.xy + offsets.xy/1024.0).r; \n } else {\n shadow += texture2D(shadowMap, texCoords.xy - offsets.xy/1024.0).r; \n }\n }\n }\n shadow /= 25.0;\n }\n return shadow; \n }\n\n void main() {\n vec3 N = normalize(vNormal);\n vec3 L = normalize(vec3(pointLight.position) - vViewPosition);\n\n float lambert = dot(N, L);\n\n float shadow = computeShadow( lightSpacePosition, frontFacing, bias, shadowMapSize, shadowMap);\n shadow = shadow * shadowStrength + shadowOffset;\n shadow = clamp(shadow, 0.1, 1.0);\n\n vec3 lightColor = pointLightColor * shadow;\n\n vec4 specular = vec4(1.0);\n if (lambert > 0.0) { \n vec3 E = normalize(vViewPosition);\n vec3 R = reflect(-L, N);\n float specularAngle = max(dot(R,E), 0.0);\n specularAngle = pow(specularAngle, shininess);\n specular.rgb = specularStrength * specularAngle * pointLightColor;\n }\n\n gl_FragColor = vec4((ambientLightColor + lightColor) * lambert + specular.rgb, opacity);\n }";
var onMouseMove = function(event) {
var boundingClientRect = canvas.getBoundingClientRect();
mouseVector.x = ((event.clientX - boundingClientRect.left) / boundingClientRect.width) * 2 - 1;
mouseVector.y = -((event.clientY - boundingClientRect.top) / boundingClientRect.height) * 2 + 1;
raycaster.setFromCamera(mouseVector, camera);
var intersects = raycaster.intersectObjects(scene.children);
if (intersects.length > 0) {
if (INTERSECTED != intersects[0].object) {
if (INTERSECTED) {
INTERSECTED.material.color.setHex(INTERSECTED.currentHex);
}
INTERSECTED = intersects[0].object;
INTERSECTED.currentHex = INTERSECTED.material.color.getHex();
plane.setFromNormalAndCoplanarPoint(camera.getWorldDirection(plane.normal), INTERSECTED.position);
}
var intersection = raycaster.intersectPlane(plane);
intersection.sub(offset);
INTERSECTED.position.copy(intersection);
INTERSECTED.currentPosition = INTERSECTED.position;
} else {
if (INTERSECTED) INTERSECTED.material.color.setHex(INTERSECTED.currentHex);
INTERSECTED = null;
}
};
function init() {
scene = new THREE.Scene();
camera = new THREE.PerspectiveCamera(70, window.innerWidth / window.innerHeight, 1, 1000);
camera.position.z = 100;
light = new THREE.AmbientLight(0xffffff);
light.position.set(50, 50, 50);
scene.add(light);
pointLight = new THREE.PointLight(0xffffff, 2, 80);
pointLight.position.set(0, 0, 75);
scene.add(pointLight);
renderer = new THREE.WebGLRenderer({antialias: true});
renderer.setClearColor(0xffffff);
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);
controls = new THREE.TrackballControls(camera, renderer.domElement);
controls.rotSpeed = 4.0;
controls.zoomSpeed = 1.2;
controls.panSpeed = 0.8;
controls.noZoom = false;
controls.noPan = false;
controls.staticMoving = true;
controls.dynamicDampingFactor = 0.3;
raycaster = new THREE.Raycaster();
mouseVector = new THREE.Vector2();
plane = new THREE.Plane();
geometry.computeVertexNormals();
mesh = new THREE.Mesh(geometry, material);
scene.add(mesh);
var gui = new dat.GUI();
var lightGui = gui.addFolder('Lighting');
var lightCon = new lighting();
lightGui.addColor(lightCon, 'ambientLightColor').onChange(function(e) {
light.color = new THREE.Color(e);
renderer.render(scene, camera);
});
lightGui.add(pointLight, 'distance', 0, 200).onChange(function(e) {
renderer.render(scene, camera);
}).listen();
lightGui.add(pointLight, 'angle', 0, Math.PI/2).onChange(function(e) {
renderer.render(scene, camera);
}).listen();
lightGui.add(pointLight, 'intensity', 0, 500000).onChange(function(e) {
renderer.render(scene, camera);
}).listen();
lightGui.add(lightCon, 'exponent', 0, 50).onChange(function(e) {
pointLight.exponent = e;
renderer.render(scene, camera);
});
lightGui.add(pointLight, 'castShadow').onChange(function(e) {
renderer.render(scene, camera);
}).listen();
lightGui.addColor(lightCon, 'pointLightColor').onChange(function(e) {
pointLight.color = new THREE.Color(e);
renderer.render(scene, camera);
});
lightGui.add(lightCon, 'distance', 0, 200).onChange(function(e) {
pointLight.distance = e;
renderer.render(scene, camera);
}).listen();
lightGui.add(lightCon, 'angle', 0, Math.PI/2).onChange(function(e) {
pointLight.angle = e;
renderer.render(scene, camera);
}).listen();
lightGui.add(lightCon, 'exponent').onChange(function(e) {
pointLight.exponent = e;
renderer.render(scene, camera);
});
lightGui.add(lightCon, 'x').onChange(function(e) {
pointLight.position.x = e;
renderer.render(scene, camera);
});
lightGui.add(lightCon, 'y').onChange(function(e) {
pointLight.position.y = e;
renderer.render(scene, camera);
});
lightGui.add(lightCon, 'z').onChange(function(e) {
pointLight.position.z = e;
renderer.render(scene, camera);
});
lightGui.open();
}
function animate() {
requestAnimationFrame(animate);
renderer.render(scene, camera);
controls.update();
}
init();
animate();
document.addEventListener('mousemove', onMouseMove, false);
总结
无障碍模式下的轨迹球定位功能可以帮助残障人士更方便地使用网络，它极大地改进了用户使用的体验。在实现轨迹球定位技术时，我们需要考虑的是如何增大轨迹球的目标区域、改变鼠标的行为以及使用轨迹球来控制页面的缩放。这些技术可以被涉及到轨迹球定位技术的领域所使用并产生积极的效果。
来源：JavaScript中文网 ，转载请注明来源 https://www.javascriptcn.com/post/64cb35f95ad90b6d041f44df