Ray Casting and Filters - WebGL Game Development - page 331

stage.stageObjects[rigidBody._id].isPicked=true;
rayCaster.pickedObject=stage.stageObjects[rigidBody._id];
};.............
}
We attach an onmousedown event to our canvas object. When the mouse is clicked,
we calculate the mouse click's x and y coordinates using the sum of offsetLeft /
offsetTop of the canvas's parent objects. Then, we invoke the pickObject function
of our rayCaster object and the pickObject function returns the object of the
selected rigidBody object. The _id parameter of the rigidBody object is retrieved.
This _id parameter is the index of the stageObject in the stageObjects array.
We retrieve the selected stageObject and set its isPicked property to true
( stage.stageObjects[rigidBody._id].isPicked=true; ) and store the selected
stageObject in the pickedObject attribute of the RayCaster class ( rayCaster.
pickedObject=stage.stageObjects[rigidBody._id]; ). The pickedObject
attribute of the RayCaster class is used to unset the isPicked property of the object
when a new object is selected.
Remember all stage objects have an associated rigidBody object, which is initialized
when the addModel function of the Stage class is invoked with the stageObject as
the parameter.
Our drawScene function is as follows:
function drawScene() {
...
for(var i=0;i<stage.stageObjects.length;++i){
...
if(stage.stageObjects[i].isPicked)
{
gl.uniform3f(shaderProgram.materialDiffuseColor,0,255,0);
}
else
{
gl.uniform3f(shaderProgram.materialDiffuseColor,
stage.stageObjects[i].diffuseColor[0],
stage.stageObjects[i].diffuseColor[1],
stage.stageObjects[i].diffuseColor[2]);
}
if(stage.stageObjects[i].materialFile!=
null&&!stage.stageObjects[i].isPicked){
gl.uniform1i(shaderProgram.hasTexture,1);
....
}