How to Build this Rounded Two Tone Donut Chart?

Question

I'm trying to make a donut chart that looks like one below

I'll be using angularJS, SVG and D3.js

I've no clue how to get those rounded ends, Please help. Thanks.

Answer 1

Simple answer: you use masks.

We use a mask to draw the inner portion of the bezel. And a mask to cut the hole in the middle.

The hole mask isn't really necessary. You could form the donut with thick lines. But it seemed easier to me to draw circular sectors, then make the hole.

Here it is in SVG form. I'll leave the conversion to D3 to you.

<svg width="600" height="600">
    <defs>
        <!-- masks out the area outside and inside the inner bevel region -->
        <mask id="innerbevel">
            <rect width="100%" height="100%" fill="black"/>
            <circle cx="0" cy="0" r="235" fill="white"/>
        </mask>
        <!-- cuts hole in centre of graph -->
        <mask id="centrehole">
            <rect x="-100%" y="-100%" width="200%" height="200%" fill="white"/>
            <circle cx="0" cy="0" r="195" fill="black"/>
        </mask>
    </defs>

    <!-- Graph is drawn centred at (0,0). The transform moves it into middle of SVG. -->
    <!-- The mask forms the hole in the centre. -->
    <g transform="translate(300,300)" mask="url(#centrehole)">
        <!-- outer bevel -->
        <g>
            <!-- light blue segment -->
            <path d="M0 0 0 -275 A 275 275 0 0 1 0 275" fill="#89e4d2"/>
            <!-- red segment -->
            <path d="M0 0 0 275 A 275 275 0 0 1 -275 0" fill="#f394a2"/>
            <!-- blue segment -->
            <path d="M0 0 -275 0 A 275 275 0 0 1 0 -275" fill="#a3a4ff"/>

            <!-- light blue rounded end -->
            <circle cx="0" cy="235" r="40" fill="#89e4d2"/>
            <!-- red rounded end -->
            <circle cx="-235" cy="0" r="40" fill="#f394a2"/>
            <!-- blue rounded end -->
            <circle cx="0" cy="-235" r="40" fill="#a3a4ff"/>
        </g>
        <!-- inner bevel - same as above but with different colours and is masked -->
        <g mask="url(#innerbevel)">
            <!-- light blue segment -->
            <path d="M0 0 0 -275 A 275 275 0 0 1 0 275" fill="#5bc8b7"/>
            <!-- red segment -->
            <path d="M0 0 0 275 A 275 275 0 0 1 -275 0" fill="#ef6974"/>
            <!-- blue segment -->
            <path d="M0 0 -275 0 A 275 275 0 0 1 0 -275" fill="#6b5dff"/>

            <!-- light blue rounded end -->
            <circle cx="0" cy="235" r="40" fill="#5bc8b7"/>
            <!-- red rounded end -->
            <circle cx="-235" cy="0" r="40" fill="#ef6974"/>
            <!-- blue rounded end -->
            <circle cx="0" cy="-235" r="40" fill="#6b5dff"/>
        </g>
    </g>

</svg>