Skinning and Animations - WebGL Game Development - page 293

This pose function is invoked whenever the DOF value of any bone is modified.
It is invoked from animation handlers and initially invoked from the RiggedMesh
constructor. The normalizeSkinWeights function is defined as follows:
RiggedMesh.prototype.normalizeSkinWeights = function () {
for ( var i = 0; i < this.geometry.skinIndices.length; i ++ ) {
var sw = this.geometry.skinWeights[ i ];
vec4.normalize(sw,sw);
}
};
This another very important function makes sure that the sum of all weights for
a vertex is equal to 1. If you open model/obj/mrgreen.json , you will notice
skinWeights=[1,1 …..] . This simply means that vertex one in the vertices array
is equally affected by both the bones in the skinIndices array. However, we need
to normalize it before we pass them to the vertex shader. The matrixWorld matrix is
updated as follows:
RiggedMesh.prototype.update=function(steps){
this.updateMatrixWorld(true);
this.updateMatrix();
}
The preceding update function simply updates the matrixWorld . The final step of
cloning is done as follows:
RiggedMesh.prototype.clone = function ( object ) {
if ( object === undefined ) {
object = new RiggedMesh( this.geometry );
}
return object;
};
Loading the skinned model
Our base classes are ready. Now, let's move on to see them in action. We will need
to modify our shaders to compute the vertex transformations. Open 08-Loading-
Skinned-Models.html in your favorite editor.
This vertex shader will now take four extra parameters, which are as follows:
• useSkinning : This is a booluniform value that determines whether the
passed vertex uses skinning or not.
• boneGlobalMatrices : This is a mat4 uniform value that holds all the offset
matrices, passed as a flattened array from the main control code.