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L_Cayla · December 8, 2018, 10:53pm

Hi,

I have started using KHR_techniques_webgl in my gltf models and it works well so far on Cesium 1.50.

However I haven’t been able to find a way to change the uniform values so far. The material does not have a name apparently so I can’t call getMaterlal and therefore can’t access their values. In fact, I haven’t seen in the specs a name see :

"materials": [
    {
        "extensions": {
            "KHR_techniques_webgl": {
                "technique": 0,
                "values" : {
                    "u_light0Color": [
                        0.8,
                        0.8,
                        1.0
                    ]
                }
            }
        }
    }
]

Is there a way to achieve what I am trying to do (change uniform values of currently loaded model)? or am I missing something?

Thanks,

-Lionel

omar · December 11, 2018, 5:25pm

This seems like a missing feature as far as I can tell. You can see the engine actually keeps track of materials by ID here:

github.com

CesiumGS/cesium/blob/master/Source/Scene/Model.js#L1694


var gltf = model.gltf;
var buffers = gltf.buffers;
var bufferViews = gltf.bufferViews;
var sourceShaders = model._rendererResources.sourceShaders;
ForEach.shader(gltf, function(shader, id) {
    // Shader references either uri (external or base64-encoded) or bufferView
    if (defined(shader.bufferView)) {
        var bufferViewId = shader.bufferView;
        var bufferView = bufferViews[bufferViewId];
        var bufferId = bufferView.buffer;
        var buffer = buffers[bufferId];
        var source = getStringFromTypedArray(buffer.extras._pipeline.source, bufferView.byteOffset, bufferView.byteLength);
        sourceShaders[id] = source;
    } else if (defined(shader.extras._pipeline.source)) {
        sourceShaders[id] = shader.extras._pipeline.source;
    } else {
        ++model._loadResources.pendingShaderLoads;


        var shaderResource = model._resource.getDerivedResource({
            url: shader.uri
        });

But doesn’t expose a way to get it. Feel free to open up a feature request on the GitHub issues (https://github.com/AnalyticalGraphicsInc/cesium/issues) to request this.

As a workaround, you could modify the glTF to give the material a name so you can access it.