Shadow map appearing on wrong place

问题

I'm trying to make use of the built-in shadow map plugin in three.js. After initial difficulties I have more or less acceptable image with one last glitch. That one being shadow appearing on top some (all?) surfaces, with normal 0,0,1. Below are pictures of the same model.

Three.js

Preview.app (Mac)

And the code used to setup shadows:

    var shadowLight = new THREE.DirectionalLight(0xFFFFFF);
    shadowLight.position.x = cx + dmax/2;
    shadowLight.position.y = cy - dmax/2;
    shadowLight.position.z = dmax*1.5;
    shadowLight.lookAt(new THREE.Vector3(cx, cy, 0));
    shadowLight.target.position.set(cx, cy, 0);
    shadowLight.castShadow = true;
    shadowLight.onlyShadow = true;
    shadowLight.shadowCameraNear    =  dmax;
    shadowLight.shadowCameraFar     =  dmax*2;
    shadowLight.shadowCameraLeft    = -dmax/2;
    shadowLight.shadowCameraRight   =  dmax/2;
    shadowLight.shadowCameraBottom  = -dmax/2;
    shadowLight.shadowCameraTop     =  dmax/2;
    shadowLight.shadowBias          =  0.005;
    shadowLight.shadowDarkness      =  0.3;
    shadowLight.shadowMapWidth      =  2048;
    shadowLight.shadowMapHeight     =  2048;
    // shadowLight.shadowCameraVisible = true;
    scene.add(shadowLight);

UPDATE: And a live example over here: http://jsbin.com/okobum/1/edit

回答1:

Your code looks fine. You just need to play with the shadowLight.shadowBias parameter. This is always a bit tricky. (Note that the bias parameter can be negative.)

EDIT: Tighten up your shadow-camera near and far planes. This will help reduce both shadow acne and peter-panning. For example, your live link, set shadowLight.shadowCameraNear = 3*dmax;. This worked for me.

You can also try adding depth to your table tops, if it's not already there.

You can try setting renderer.shadowMapCullFrontFaces = false. This will cull back faces instead of front ones.

来源：https://stackoverflow.com/questions/12912126/shadow-map-appearing-on-wrong-place

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javascript

WebGL

three.js