Improve vertex transformation system

This migrates TurtleMultiModel's current vertex transformation system
into something more powerful and "correct". Namely, it has the following
improvements:

 - Handles all position formats (float, byte, etc...)
 - Correctly translates normals of quads
 - Reorders faces if the winding order is reversed

src/main/java/dan200/computercraft/client/render/ModelTransformer.java

@@ -0,0 +1,264 @@
+package dan200.computercraft.client.render;
+
+import net.minecraft.client.renderer.block.model.BakedQuad;
+import net.minecraft.client.renderer.texture.TextureAtlasSprite;
+import net.minecraft.client.renderer.vertex.VertexFormat;
+import net.minecraft.util.EnumFacing;
+import net.minecraftforge.client.model.pipeline.IVertexConsumer;
+import net.minecraftforge.client.model.pipeline.LightUtil;
+import net.minecraftforge.client.model.pipeline.VertexTransformer;
+import net.minecraftforge.common.model.TRSRTransformation;
+
+import javax.annotation.Nonnull;
+import javax.vecmath.Matrix4f;
+import javax.vecmath.Point3f;
+import javax.vecmath.Vector3f;
+import java.util.List;
+
+/**
+ * Transforms vertices of a model, remaining aware of winding order, and rearranging
+ * vertices if needed.
+ */
+public final class ModelTransformer
+{
+    private static final Matrix4f identity;
+
+    static
+    {
+        identity = new Matrix4f();
+        identity.setIdentity();
+    }
+
+    private ModelTransformer()
+    {
+    }
+
+    public static void transformQuadsTo( List<BakedQuad> output, List<BakedQuad> input, Matrix4f transform )
+    {
+        if( transform == null || transform.equals( identity ) )
+        {
+            output.addAll( input );
+        }
+        else
+        {
+            Matrix4f normalMatrix = new Matrix4f( transform );
+            normalMatrix.invert();
+            normalMatrix.transpose();
+
+            for( BakedQuad quad : input ) output.add( doTransformQuad( quad, transform, normalMatrix ) );
+        }
+    }
+
+    public static BakedQuad transformQuad( BakedQuad input, Matrix4f transform )
+    {
+        if( transform == null || transform.equals( identity ) ) return input;
+
+        Matrix4f normalMatrix = new Matrix4f( transform );
+        normalMatrix.invert();
+        normalMatrix.transpose();
+        return doTransformQuad( input, transform, normalMatrix );
+    }
+
+    private static BakedQuad doTransformQuad( BakedQuad input, Matrix4f positionMatrix, Matrix4f normalMatrix )
+    {
+
+        BakedQuadBuilder builder = new BakedQuadBuilder( input.getFormat() );
+        NormalAwareTransformer transformer = new NormalAwareTransformer( builder, positionMatrix, normalMatrix );
+        input.pipe( transformer );
+
+        if( transformer.areNormalsInverted() )
+        {
+            builder.swap( 1, 3 );
+            transformer.areNormalsInverted();
+        }
+
+        return builder.build();
+    }
+
+    /**
+     * A vertex transformer that tracks whether the normals have been inverted and so the vertices
+     * should be reordered so backface culling works as expected.
+     */
+    private static class NormalAwareTransformer extends VertexTransformer
+    {
+        private final Matrix4f positionMatrix;
+        private final Matrix4f normalMatrix;
+
+        private int vertexIndex = 0, elementIndex = 0;
+        private final Point3f[] before = new Point3f[ 4 ];
+        private final Point3f[] after = new Point3f[ 4 ];
+
+        public NormalAwareTransformer( IVertexConsumer parent, Matrix4f positionMatrix, Matrix4f normalMatrix )
+        {
+            super( parent );
+            this.positionMatrix = positionMatrix;
+            this.normalMatrix = normalMatrix;
+        }
+
+        @Override
+        public void setQuadOrientation( EnumFacing orientation )
+        {
+            super.setQuadOrientation( orientation == null ? orientation : TRSRTransformation.rotate( positionMatrix, orientation ) );
+        }
+
+        @Override
+        public void put( int element, @Nonnull float... data )
+        {
+            switch( getVertexFormat().getElement( element ).getUsage() )
+            {
+                case POSITION:
+                {
+                    Point3f vec = new Point3f( data );
+                    Point3f newVec = new Point3f();
+                    positionMatrix.transform( vec, newVec );
+
+                    float[] newData = new float[ 4 ];
+                    newVec.get( newData );
+                    super.put( element, newData );
+
+
+                    before[ vertexIndex ] = vec;
+                    after[ vertexIndex ] = newVec;
+                    break;
+                }
+                case NORMAL:
+                {
+                    Vector3f vec = new Vector3f( data );
+                    normalMatrix.transform( vec );
+
+                    float[] newData = new float[ 4 ];
+                    vec.get( newData );
+                    super.put( element, newData );
+                    break;
+                }
+                default:
+                    super.put( element, data );
+                    break;
+            }
+
+            elementIndex++;
+            if( elementIndex == getVertexFormat().getElementCount() )
+            {
+                vertexIndex++;
+                elementIndex = 0;
+            }
+        }
+
+        public boolean areNormalsInverted()
+        {
+            Vector3f temp1 = new Vector3f(), temp2 = new Vector3f();
+            Vector3f crossBefore = new Vector3f(), crossAfter = new Vector3f();
+
+            // Determine what cross product we expect to have
+            temp1.sub( before[ 1 ], before[ 0 ] );
+            temp2.sub( before[ 1 ], before[ 2 ] );
+            crossBefore.cross( temp1, temp2 );
+            normalMatrix.transform( crossBefore );
+
+            // And determine what cross product we actually have
+            temp1.sub( after[ 1 ], after[ 0 ] );
+            temp2.sub( after[ 1 ], after[ 2 ] );
+            crossAfter.cross( temp1, temp2 );
+
+            // If the angle between expected and actual cross product is greater than 
+            // pi/2 radians then we will need to reorder our quads.
+            return Math.abs( crossBefore.angle( crossAfter ) ) >= Math.PI / 2;
+        }
+    }
+
+    /**
+     * A vertex consumer which is capable of building {@link BakedQuad}s.
+     *
+     * Equivalent to {@link net.minecraftforge.client.model.pipeline.UnpackedBakedQuad.Builder} but more memory
+     * efficient.
+     *
+     * This also provides the ability to swap vertices through {@link #swap(int, int)} to allow reordering.
+     */
+    private static class BakedQuadBuilder implements IVertexConsumer
+    {
+        private final VertexFormat format;
+
+        private final int[] vertexData;
+        private int vertexIndex = 0, elementIndex = 0;
+
+        private EnumFacing orientation;
+        private int quadTint;
+        private boolean diffuse;
+        private TextureAtlasSprite texture;
+
+        private BakedQuadBuilder( VertexFormat format )
+        {
+            this.format = format;
+            this.vertexData = new int[ format.getNextOffset() ];
+        }
+
+        @Nonnull
+        @Override
+        public VertexFormat getVertexFormat()
+        {
+            return format;
+        }
+
+        @Override
+        public void setQuadTint( int tint )
+        {
+            this.quadTint = tint;
+        }
+
+        @Override
+        public void setQuadOrientation( @Nonnull EnumFacing orientation )
+        {
+            this.orientation = orientation;
+        }
+
+        @Override
+        public void setApplyDiffuseLighting( boolean diffuse )
+        {
+            this.diffuse = diffuse;
+        }
+
+        @Override
+        public void setTexture( @Nonnull TextureAtlasSprite texture )
+        {
+            this.texture = texture;
+        }
+
+        @Override
+        public void put( int element, @Nonnull float... data )
+        {
+            LightUtil.pack( data, vertexData, format, vertexIndex, element );
+
+            elementIndex++;
+            if( elementIndex == getVertexFormat().getElementCount() )
+            {
+                vertexIndex++;
+                elementIndex = 0;
+            }
+        }
+
+        public void swap( int a, int b )
+        {
+            int length = vertexData.length / 4;
+            for( int i = 0; i < length; i++ )
+            {
+                int temp = vertexData[ a * length + i ];
+                vertexData[ a * length + i ] = vertexData[ b * length + i ];
+                vertexData[ b * length + i ] = temp;
+            }
+        }
+
+        public BakedQuad build()
+        {
+            if( elementIndex != 0 || vertexIndex != 4 )
+            {
+                throw new IllegalStateException( "Got an unexpected number of elements/vertices" );
+            }
+            if( texture == null )
+            {
+                throw new IllegalStateException( "Texture has not been set" );
+            }
+
+            return new BakedQuad( vertexData, quadTint, orientation, texture, diffuse, format );
+        }
+    }
+}

src/main/java/dan200/computercraft/client/render/TurtleMultiModel.java

@@ -6,13 +6,10 @@ import net.minecraft.client.renderer.block.model.IBakedModel;
 import net.minecraft.client.renderer.block.model.ItemCameraTransforms;
 import net.minecraft.client.renderer.block.model.ItemOverrideList;
 import net.minecraft.client.renderer.texture.TextureAtlasSprite;
-import net.minecraft.client.renderer.vertex.VertexFormat;
-import net.minecraft.client.renderer.vertex.VertexFormatElement;
 import net.minecraft.util.EnumFacing;
 
 import javax.annotation.Nonnull;
 import javax.vecmath.Matrix4f;
-import javax.vecmath.Point3f;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
@@ -48,29 +45,17 @@ public class TurtleMultiModel implements IBakedModel
     {
         if( side != null )
         {
-            if( !m_faceQuads.containsKey( side ) )
-            {
-                ArrayList<BakedQuad> quads = new ArrayList<>();
-                if( m_overlayModel != null )
-                {
-                    quads.addAll( m_overlayModel.getQuads( state, side, rand ) );
-                }
-                if( m_leftUpgradeModel != null )
-                {
-                    quads.addAll( transformQuads( m_leftUpgradeModel.getQuads( state, side, rand ), m_leftUpgradeTransform ) );
-                }
-                if( m_rightUpgradeModel != null )
-                {
-                    quads.addAll( transformQuads( m_rightUpgradeModel.getQuads( state, side, rand ), m_rightUpgradeTransform ) );
-                }
-                quads.trimToSize();
-                m_faceQuads.put( side, quads );
-            }
+            if( !m_faceQuads.containsKey( side ) ) m_faceQuads.put( side, buildQuads( state, side, rand ) );
             return m_faceQuads.get( side );
         }
         else
         {
-            if( m_generalQuads == null )
+            if( m_generalQuads == null ) m_generalQuads = buildQuads( state, side, rand );
+            return m_generalQuads;
+        }
+    }
+
+    private List<BakedQuad> buildQuads( IBlockState state, EnumFacing side, long rand )
     {
         ArrayList<BakedQuad> quads = new ArrayList<>();
         quads.addAll( m_baseModel.getQuads( state, side, rand ) );
@@ -80,17 +65,14 @@ public class TurtleMultiModel implements IBakedModel
         }
         if( m_leftUpgradeModel != null )
         {
-                    quads.addAll( transformQuads( m_leftUpgradeModel.getQuads( state, side, rand ), m_leftUpgradeTransform ) );
+            ModelTransformer.transformQuadsTo( quads, m_leftUpgradeModel.getQuads( state, side, rand ), m_leftUpgradeTransform );
         }
         if( m_rightUpgradeModel != null )
         {
-                    quads.addAll( transformQuads( m_rightUpgradeModel.getQuads( state, side, rand ), m_rightUpgradeTransform ) );
+            ModelTransformer.transformQuadsTo( quads, m_rightUpgradeModel.getQuads( state, side, rand ), m_rightUpgradeTransform );
         }
         quads.trimToSize();
-                m_generalQuads = quads;
-            }
-            return m_generalQuads;
-        }
+        return quads;
     }
 
     @Override
@@ -132,63 +114,4 @@ public class TurtleMultiModel implements IBakedModel
     {
         return ItemOverrideList.NONE;
     }
-
-    private List<BakedQuad> transformQuads( List<BakedQuad> input, Matrix4f transform )
-    {
-        if( transform == null || input.size() == 0 )
-        {
-            return input;
-        }
-        else
-        {
-            List<BakedQuad> output = new ArrayList<>( input.size() );
-            for( BakedQuad quad : input )
-            {
-                output.add( transformQuad( quad, transform ) );
-            }
-            return output;
-        }
-    }
-
-    private BakedQuad transformQuad( BakedQuad quad, Matrix4f transform )
-    {
-        int[] vertexData = quad.getVertexData().clone();
-        int offset = 0;
-        BakedQuad copy = new BakedQuad( vertexData, -1, quad.getFace(), quad.getSprite(), quad.shouldApplyDiffuseLighting(), quad.getFormat() );
-        VertexFormat format = copy.getFormat();
-        for( int i=0; i<format.getElementCount(); ++i ) // For each vertex element
-        {
-            VertexFormatElement element = format.getElement( i );
-            if( element.isPositionElement() &&
-                element.getType() == VertexFormatElement.EnumType.FLOAT &&
-                element.getElementCount() == 3 ) // When we find a position element
-            {
-                for( int j=0; j<4; ++j ) // For each corner of the quad
-                {
-                    int start = offset + j * format.getNextOffset();
-                    if( (start % 4) == 0 )
-                    {
-                        start = start / 4;
-
-                        // Extract the position
-                        Point3f pos = new Point3f(
-                            Float.intBitsToFloat( vertexData[ start ] ),
-                            Float.intBitsToFloat( vertexData[ start + 1 ] ),
-                            Float.intBitsToFloat( vertexData[ start + 2 ] )
-                        );
-
-                        // Transform the position
-                        transform.transform( pos );
-
-                        // Insert the position
-                        vertexData[ start ] = Float.floatToRawIntBits( pos.x );
-                        vertexData[ start + 1 ] = Float.floatToRawIntBits( pos.y );
-                        vertexData[ start + 2 ] = Float.floatToRawIntBits( pos.z );
-                    }
-                }
-            }
-            offset += element.getSize();
-        }
-        return copy;
-    }
 }