while alpha blackground，png has black

[tianlv777]

var renderer = new THREE.WebGLRenderer({ canvas: canvas, alpha: true});
how to let black be transparent？

[durswd]

I think that It need to draw a background with WebGL.
But it is not a good way to do it.
I ask a WebGL specialist about it

[tianlv777]

Now I had solved it by let change png image to alpha background.But the new question is urho3d how to use this tool.