Reapply "revert mipmap generation in envbaking"

This reverts commit c39e790.

Author: riccardobl

jme3-core/src/main/java/com/jme3/environment/baker/GenericEnvBaker.java

@@ -57,7 +57,6 @@
 import com.jme3.texture.Texture.WrapMode;
 import com.jme3.texture.TextureCubeMap;
 import com.jme3.texture.image.ColorSpace;
-import com.jme3.util.BufferUtils;
 
 /**
  * Render the environment into a cubemap
@@ -116,12 +115,9 @@ protected GenericEnvBaker(RenderManager rm, AssetManager am, Format colorFormat,
 
         envMap = new TextureCubeMap(env_size, env_size, colorFormat);
         envMap.setMagFilter(MagFilter.Bilinear);
-        // Specular prefiltering samples the captured environment with explicit
-        // source LODs, so the capture texture must keep a mip chain available.
-        envMap.setMinFilter(MinFilter.Trilinear);
+        envMap.setMinFilter(MinFilter.BilinearNoMipMaps);
         envMap.setWrap(WrapMode.EdgeClamp);
         envMap.getImage().setColorSpace(ColorSpace.Linear);
-        initializeCubemapFacesToBlack(envMap);
     }
 
     @Override
@@ -177,7 +173,6 @@ public void bakeEnvironment(Spatial scene, Vector3f position, float frustumNear,
             envbakers[i].setDepthTarget(FrameBufferTarget.newTarget(depthFormat));
             envbakers[i].setSrgb(false);
             envbakers[i].addColorTarget(FrameBufferTarget.newTarget(envMap).face(TextureCubeMap.Face.values()[i]));
-            envbakers[i].setMipMapsGenerationHint(i == 5);
         }
 
         if (isTexturePulling()) {
@@ -294,13 +289,4 @@ protected int limitMips(int nbMipMaps, int baseW, int baseH, RenderManager rm) {
         return nbMipMaps;
     }
 
-    private void initializeCubemapFacesToBlack(TextureCubeMap cubemap) {
-        int bytesPerPixel = cubemap.getImage().getFormat().getBitsPerPixel() / 8;
-        int faceSize = cubemap.getImage().getWidth() * cubemap.getImage().getHeight() * bytesPerPixel;
-        for (int i = 0; i < 6; i++) {
-            cubemap.getImage().setData(i, BufferUtils.createByteBuffer(faceSize));
-        }
-        cubemap.getImage().setUpdateNeeded();
-    }
-
 }

jme3-core/src/main/resources/Common/IBL/IBLKernels.frag

@@ -78,16 +78,6 @@ void prefilteredEnvKernel(){
 
     float roughness = clamp(m_Roughness, 0.0, 1.0);
     float alpha = roughness * roughness;
-    float envMapResolution = float(textureSize(m_EnvMap, 0).x);
-    float texelSolidAngle = (4.0 * PI) / max(6.0 * envMapResolution * envMapResolution, 1.0);
-    float maxSourceLod = max(log2(envMapResolution), 0.0);
-
-    // The GGX distribution becomes singular for an ideal mirror. For mip 0,
-    // skip the importance-sampled integration and keep the sharp source env.
-    if (roughness <= 0.0) {
-        outFragColor = vec4(textureLod(m_EnvMap, R, 0.0).rgb, 1.0);
-        return;
-    }
 
     const uint SAMPLE_COUNT = 1024u;
     float totalWeight = 0.0;   
@@ -99,14 +89,7 @@ void prefilteredEnvKernel(){
         vec3 L  = normalize(2.0 * VoH * H - V);
         float NdotL = max(dot(N, L), 0.0);
         if(NdotL > 0.0) {
-            float NdotH = max(dot(N, H), 0.0);
-            float pdf = ImportanceSampleGGXPdf(NdotH, VoH, alpha);
-            float sampleSolidAngle = 1.0 / max(float(SAMPLE_COUNT) * pdf, 1e-4);
-            // Approximate each cubemap texel as equal-area and select a source mip
-            // from the ratio between the GGX sample cone and a texel footprint.
-            float sourceLod = roughness <= 0.0 ? 0.0 : 0.5 * log2(sampleSolidAngle / texelSolidAngle);
-            sourceLod = clamp(sourceLod, 0.0, maxSourceLod);
-            vec3 sampleColor = textureLod(m_EnvMap, L, sourceLod).rgb;
+            vec3 sampleColor = texture(m_EnvMap, L).rgb;
             prefilteredColor += sampleColor * NdotL;
             totalWeight      += NdotL;
         }