const m4 = twgl.m4;
const gl = document.querySelector("canvas").getContext("webgl");
const ext = gl.getExtension("OES_standard_derivatives");
const vs = `
attribute vec4 position;
uniform mat4 u_worldViewProjection;
varying vec3 v_position;
void main() {
gl_Position = u_worldViewProjection * position;
v_position = position.xyz; // for fake lighting
}
`;
const fs = `
#extension GL_OES_standard_derivatives : enable
precision mediump float;
varying vec3 v_position;
uniform vec4 u_color;
void main() {
vec3 fdx = dFdx(v_position);
vec3 fdy = dFdy(v_position);
vec3 n = normalize(cross(fdx,fdy));
float l = dot(n, normalize(vec3(1,2,-3))) * .5 + .5;
gl_FragColor = u_color;
gl_FragColor.rgb *= l;
}
`;
const programInfo = twgl.createProgramInfo(gl, [vs, fs]);
const arrays = {
position: [
-1, 1, -1,
1, 1, -1,
1, -1, -1,
-1, -1, -1,
-1, 1, 1,
1, 1, 1,
1, -1, 1,
-1, -1, 1,
],
indices: [
0, 1, 1, 2, 2, 3, 3, 0,
4, 5, 5, 6, 6, 7, 7, 4,
0, 4, 1, 5, 2, 6, 3, 7,
],
};
const concat = twgl.primitives.concatVertices;
const reorient = twgl.primitives.reorientVertices;
const wireCubeBufferInfo = twgl.createBufferInfoFromArrays(gl, arrays);
const solidCubeBufferInfo = twgl.primitives.createCubeBufferInfo(gl, 2);
const cameraBufferInfo = twgl.createBufferInfoFromArrays(gl,
concat([
reorient(twgl.primitives.createCubeVertices(2),
m4.translation([0, 0, 1])),
reorient(twgl.primitives.createTruncatedConeVertices(0, 1, 2, 12, 1),
m4.rotationX(Math.PI * -.5)),
])
);
const black = [0, 0, 0, 1];
const blue = [0, 0, 1, 1];
function drawScene(viewProjection, clearColor) {
gl.clearColor(...clearColor);
gl.clear(gl.COLOR_BUFFER_BIT);
const numCubes = 10;
for (let i = 0; i < numCubes; ++i) {
const u = i / numCubes;
let mat = m4.rotationY(u * Math.PI * 2);
mat = m4.translate(mat, [0, 0, 10]);
mat = m4.scale(mat, [1, 1 + u * 23 % 1, 1]);
mat = m4.translate(mat, [0, .5, 0]);
mat = m4.multiply(viewProjection, mat);
drawModel(solidCubeBufferInfo, mat, [u, u * 3 % 1, u * 7 % 1,1]);
}
}
function drawModel(bufferInfo, worldViewProjection, color, mode) {
twgl.setBuffersAndAttributes(gl, programInfo, bufferInfo);
twgl.setUniforms(programInfo, {
u_worldViewProjection: worldViewProjection,
u_color: color,
});
twgl.drawBufferInfo(gl, bufferInfo, mode);
}
function render(time) {
time *= 0.001;
twgl.resizeCanvasToDisplaySize(gl.canvas);
const width = gl.canvas.width;
const height = gl.canvas.height;
const halfWidth = width / 2;
gl.viewport(0, 0, width, height);
gl.disable(gl.SCISSOR_TEST);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
gl.enable(gl.DEPTH_TEST);
let projectionToViewWith;
{
const fov = 60 * Math.PI / 180;
const aspect = gl.canvas.clientWidth / 2 / gl.canvas.clientHeight;
const zNear = 0.5;
const zFar = 100;
projectionToViewWith = m4.perspective(fov, aspect, zNear, zFar);
}
let projectionToBeViewed;
{
const fov = 60 * Math.PI / 180;
const aspect = gl.canvas.clientWidth / 2 / gl.canvas.clientHeight;
const zNear = 1.5;
const zFar = 15;
projectionToBeViewed = m4.perspective(fov, aspect, zNear, zFar);
}
const inverseProjectionToBeViewed = m4.inverse(projectionToBeViewed);
let cameraViewingScene;
{
const t1 = 0;
const radius = 30;
const eye = [Math.sin(t1) * radius, 4, Math.cos(t1) * radius];
const target = [0, 0, 0];
const up = [0, 1, 0];
cameraViewingScene = m4.lookAt(eye, target, up);
}
let cameraInScene;
{
const t1 = time;
const t2 = time + .4;
const r1 = 10 + Math.sin(t1);
const r2 = 10 + Math.sin(t2) * 2;
const eye = [Math.sin(t1) * r1, 0 + Math.sin(t1) * 4, Math.cos(t1) * r1];
const target = [Math.sin(t2) * r2, 1 + Math.sin(t2), Math.cos(t2) * r2];
const up = [0, 1, 0];
cameraInScene = m4.lookAt(eye, target, up);
}
gl.useProgram(programInfo.program);
gl.enable(gl.SCISSOR_TEST);
gl.scissor(0, 0, halfWidth, height);
gl.viewport(0, 0, halfWidth, height);
{
const view = m4.inverse(cameraInScene);
const viewProjection = m4.multiply(projectionToBeViewed, view);
drawScene(viewProjection, [.9, 1, .9, 1]);
}
gl.scissor(halfWidth, 0, halfWidth, height);
gl.viewport(halfWidth, 0, halfWidth, height);
{
const view = m4.inverse(cameraViewingScene);
const viewProjection = m4.multiply(projectionToViewWith, view);
drawScene(viewProjection, [.9, 1, 1, 1]);
{
const world = m4.multiply(cameraInScene, inverseProjectionToBeViewed);
const worldViewProjection = m4.multiply(viewProjection, world);
drawModel(wireCubeBufferInfo, worldViewProjection, black, gl.LINES);
}
{
const worldViewProjection = m4.multiply(viewProjection, cameraInScene);
drawModel(cameraBufferInfo, worldViewProjection, blue);
}
}
requestAnimationFrame(render);
}
requestAnimationFrame(render);
body { margin: 0; }
canvas { width: 100vw; height: 100vh; display: block; }
<script src="https://twgljs.org/dist/4.x/twgl-full.min.js"></script>
<canvas></canvas>
temp = V * inverseProjectionMatrix; newV = temp.xyz / temp.w
- gman