add uploadTexture to WebGLRenderer

[henri-astre-msft]

Hi,

The goal of this PR is to provide a manual way of uploading texture.
The default behavior (needsUpdate=true) is well suited for gaming were all resources are loaded at start time.
But for a streaming solution (like in Photosynth2) this is actually hurting performance.
In Photosynth2 textures are uploaded in a loop which is suppose to not exceed ~7ms per frame, remaining textures are uploaded in consecutive frames.
Exposing this method let the user decide of his own strategy on when to upload texture.

Let me know if you find this useful or if there is any bug.
The diff is hard to read due to the new indentation but the change is actually pretty minimal.

Thanks,
--Henri

[WestLangley]

Can you provide an example of the usage pattern for this new feature?

[henri-astre-msft]

Let me know if this example is enough:

//Fake viewer
var viewer = new function() {

    var _renderer; //WebGLRenderer

    var _textureToUpload = [];

    this.loadTexture = function(tex) {
        _textureToUpload.push(tex);
    };

    function onFrameUpdate() { //callback fired by window.requestAnimationFrame
        var startTime = Date.now();

        //upload textures in the queue to GPU within the time budget
        while (_textureToUpload.length > 0) {
            var tex = _textureToUpload.shift();
            _renderer.uploadTexture(tex);
            if (Date.now()-startTime > 7) //max total upload time = ~7ms
                return;
        }
    }
};

//Usage

//Download img content, then create a texture object
var tex = new THREE.Texture(img);
tex.needsUpdate = false;
tex.onUpdate = function() {
    //triggered when the texture has been uploaded to GPU
};

//submit the texture to the queue of texture to be uploaded
viewer.loadTexture(tex);

Thanks,
--Henri

[mrdoob]

There are other calls to this.setTexture in WebGLRenderer itself which also rely in the slot parameter. Do you mind taking a look?

[mrdoob]

Ah wait. Ignore that, just saw that the setTexture is still there...

[henri-astre-msft]

Yes, the diff is hard to read in github due to the new tab indent. But the change is actually very minimal. I'm just exposing uploadTexture() and the behavior of setTexture() is left unchanged.

[mrdoob]

Yep yep! Looks good! :)

[mrdoob]

Thanks!