threejs canvas todataurl is blank

Question

Okay, I know that canvas.toDataUrl() will produce an image in png format. However, when I try to get the image from http://threejs.org/examples/#webgl_lines_sphere. All I see is a black image on chrome. To replicate the steps -

1) Open dev console and select the canvas element. 2) canvas = $0 3) context = canvas.getContext('webgl', {preserveDrawingBuffer: true}) 4) img = canvas.toDataUrl() 5) document.write('<img src="'+img+'"/>')

The image is blank. However, I tried with a different canvas at link http://threejs.org/examples/#canvas_geometry_cube. Please do the following steps to replicate.

1) Open dev console and select the canvas element. 2) canvas = $0 3) context = canvas.getContext('2d', {preserveDrawingBuffer: true}) 4) img = canvas.toDataUrl() 5) document.write('<img src="'+img+'"/>')

This gave the expected result. Why is there a difference and how can this be avoided to retrieve first image too?

Answer 1

I was also getting a solid black image.

My code previously was:

this.renderer = new THREE.WebGLRenderer({premultipliedAlpha: false});

I have changed the parameter in the THREE.WebGLRenderer to:

this.renderer = new THREE.WebGLRenderer({preserveDrawingBuffer: true});

I am getting an image on taking a snapshot.

Hope it helps.