Shadows: make sure to clear all buffers

jme3-core/src/main/java/com/jme3/shadow/AbstractShadowRenderer.java

@@ -424,7 +424,7 @@ public abstract class AbstractShadowRenderer implements SceneProcessor, Savable
         renderManager.setCamera(shadowCam, false);
 
         renderManager.getRenderer().setFrameBuffer(shadowFB[shadowMapIndex]);
-        renderManager.getRenderer().clearBuffers(false, true, false);
+        renderManager.getRenderer().clearBuffers(true, true, true);
 
         // render shadow casters to shadow map
         viewPort.getQueue().renderShadowQueue(shadowMapOccluders, renderManager, shadowCam, true);

jme3-core/src/main/java/com/jme3/shadow/BasicShadowRenderer.java

@@ -190,7 +190,7 @@ public class BasicShadowRenderer implements SceneProcessor {
         renderManager.setForcedMaterial(preshadowMat);
 
         r.setFrameBuffer(shadowFB);
-        r.clearBuffers(false, true, false);
+        r.clearBuffers(true, true, true);
         viewPort.getQueue().renderShadowQueue(shadowOccluders, renderManager, shadowCam, true);
         r.setFrameBuffer(viewPort.getOutputFrameBuffer());
 

jme3-core/src/main/java/com/jme3/shadow/PssmShadowRenderer.java

@@ -450,7 +450,7 @@ public class PssmShadowRenderer implements SceneProcessor {
             }
 
             r.setFrameBuffer(shadowFB[i]);
-            r.clearBuffers(false, true, false);
+            r.clearBuffers(true, true, true);
 
             // render shadow casters to shadow map
             viewPort.getQueue().renderShadowQueue(splitOccluders, renderManager, shadowCam, true);