Dots pattern with fancy fadeout

client/index.js

@@ -26,6 +26,8 @@ const config = {
     stroke_texture_size: 1024, // means no more than 1024^2 = 1M strokes in total (this is a LOT. HMH blackboard has like 80K)
     dynamic_stroke_texture_size: 128, // means no more than 128^2 = 16K dynamic strokes at once
     bvh_fullnode_depth: 5,
+    pattern_fadeout_min: 0.3,
+    pattern_fadeout_max: 0.75,
     benchmark: {
         zoom_level: -75,
         offset: { x: 425, y: -1195 },

client/webgl_draw.js

@@ -106,16 +106,21 @@ async function draw(state, context) {
     gl.useProgram(context.programs['pattern'].dots);
     buffers = context.buffers['pattern'];
     locations = context.locations['pattern'].dots;
-    {
+
+    if (state.canvas.zoom >= config.pattern_fadeout_min) {
         // Reused data
         gl.bindBuffer(gl.ARRAY_BUFFER, buffers['b_dot']);
-        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([10, 0, 20, 0, 10, 10]), gl.STREAM_DRAW);
+        
+        const one_dot = new Float32Array(geometry_gen_circle(0, 0, 1, 32));
+        const dot_instances = new Float32Array(geometry_gen_fullscreen_grid(state, context, 32, 32, 50, 50));
+
+        gl.bufferData(gl.ARRAY_BUFFER, one_dot, gl.STREAM_DRAW);
         gl.enableVertexAttribArray(locations['a_xy']);
         gl.vertexAttribPointer(locations['a_xy'],     2, gl.FLOAT, false, 2 * 4, 0);
 
         // Per-instance data
         gl.bindBuffer(gl.ARRAY_BUFFER, buffers['b_instance']);
-        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([100, 100, 150, 150, 10, 10, 200, 10]), gl.STREAM_DRAW);
+        gl.bufferData(gl.ARRAY_BUFFER, dot_instances, gl.STREAM_DRAW);
         gl.enableVertexAttribArray(locations['a_center']);
         gl.vertexAttribPointer(locations['a_center'], 2, gl.FLOAT, false, 2 * 4, 0);
         gl.vertexAttribDivisor(locations['a_center'], 1);
@@ -124,9 +129,17 @@ async function draw(state, context) {
         gl.uniform2f(locations['u_scale'], state.canvas.zoom, state.canvas.zoom);
         gl.uniform2f(locations['u_translation'], state.canvas.offset.x, state.canvas.offset.y);
         
-        gl.drawArraysInstanced(gl.TRIANGLES, 0, 3, 4); 
+        if (config.pattern_fadeout_min <= state.canvas.zoom && state.canvas.zoom <= config.pattern_fadeout_max) {
+            const t = (state.canvas.zoom - config.pattern_fadeout_min) / (config.pattern_fadeout_max - config.pattern_fadeout_min);
+            gl.uniform1f(locations['u_fadeout'], t);
+        } else {
+            gl.uniform1f(locations['u_fadeout'], 1);
         }
 
+        gl.drawArraysInstanced(gl.TRIANGLES, 0, one_dot.length / 2, dot_instances.length / 2); 
+    }
+
+    gl.clear(gl.DEPTH_BUFFER_BIT);
     gl.useProgram(context.programs['sdf'].main);
     buffers = context.buffers['sdf'];
     locations = context.locations['sdf'].main;

client/webgl_geometry.js

@@ -247,3 +247,42 @@ function image_at(state, x, y) {
 
     return null;
 }
+
+function geometry_gen_circle(cx, cy, r, n) {
+    const step = 2 * Math.PI / n;
+    const result = [];
+
+    for (let i = 0; i < n; ++i) {
+        const theta = i * step;
+        const next_theta = (i < n - 1 ? (i + 1) * step : 0);
+        const x = cx + r * Math.cos(theta);
+        const y = cy + r * Math.sin(theta);
+        const next_x = cx + r * Math.cos(next_theta);
+        const next_y = cy + r * Math.sin(next_theta);
+        result.push(cx, cy, x, y, next_x, next_y);
+    }
+
+    return result;
+}
+
+function geometry_gen_fullscreen_grid(state, context, step_x, step_y, offset_x, offset_y) {
+    const result = [];
+    const width = context.canvas.width;
+    const height = context.canvas.height;
+    const topleft = screen_to_canvas(state, {'x': 0, 'y': 0});
+    const bottomright = screen_to_canvas(state, {'x': width, 'y': height});
+
+    topleft.x = Math.floor(topleft.x / step_x) * step_x;
+    topleft.y = Math.ceil(topleft.y / step_y) * step_y;
+
+    bottomright.x = Math.floor(bottomright.x / step_x) * step_x;
+    bottomright.y = Math.ceil(bottomright.y / step_y) * step_y;
+
+    for (let y = topleft.y; y <= bottomright.y; y += step_y) {
+        for (let x = topleft.x; x <= bottomright.x; x += step_x) {
+            result.push(x, y);
+        }
+    }
+
+    return result;
+}

client/webgl_shaders.js

@@ -253,12 +253,29 @@ const dots_vs_src = `#version 300 es
     in vec2 a_xy;
     in vec2 a_center; // per-instance
 
+    out float v_dist;
+    out float v_fadeout;
+
     uniform vec2 u_scale;
     uniform vec2 u_res;
     uniform vec2 u_translation;
+    uniform float u_fadeout;
 
     void main() {
-        vec2 screen02 = ((a_center + a_xy) * u_scale + u_translation) / u_res * 2.0;
+        float apron = 2.0; 
+        vec2 pixel = vec2(2.0) / u_res * apron;
+        vec2 outwards = vec2(0.0);
+        float rscale = apron / u_scale.x;
+
+        if (gl_VertexID % 3 == 0) {
+            v_dist = 0.0;
+        } else {
+            outwards = a_xy;
+            v_dist = 1.0 + rscale;
+        }
+
+        v_fadeout = u_fadeout;
+        vec2 screen02 = ((a_center + a_xy) * u_scale + u_translation) / u_res * 2.0 + outwards * pixel;
         screen02.y = 2.0 - screen02.y;
         gl_Position = vec4(screen02 - 1.0, 0.0, 1.0);
     }
@@ -267,12 +284,20 @@ const dots_vs_src = `#version 300 es
 const dots_fs_src = `#version 300 es
     precision highp float;
 
+    in float v_dist;
+    in float v_fadeout;
+
     layout(location = 0) out vec4 FragColor;
 
     void main() {
-        FragColor = vec4(0.0, 0.0, 0.0, 1.0);
+        float fade = 0.5 * length(fwidth(v_dist));
+        float alpha = 1.0 - smoothstep(-fade, fade, v_dist - 1.0);
+        alpha *= v_fadeout;
+        vec3 color = vec3(0.8);
+        FragColor = vec4(color * alpha, alpha);
     }
 `;
+
 function init_webgl(state, context) {
     context.canvas = document.querySelector('#c');
     context.gl = context.canvas.getContext('webgl2', {
@@ -363,6 +388,7 @@ function init_webgl(state, context) {
             'u_res':             gl.getUniformLocation(context.programs['pattern'].dots, 'u_res'),
             'u_scale':           gl.getUniformLocation(context.programs['pattern'].dots, 'u_scale'),
             'u_translation':     gl.getUniformLocation(context.programs['pattern'].dots, 'u_translation'),
+            'u_fadeout':         gl.getUniformLocation(context.programs['pattern'].dots, 'u_fadeout'),
         }
     };