medfall

commit 9ca5e450d66a8c3e22bbf6a3c5084bbeea9682fe
parent 8ddb8f37ce2c412212502031a87497ad9dd306d4
Author: Michael Savage <mikejsavage@gmail.com>
Date:   Wed Oct 26 19:59:56 +0300

Simpler normalmap generation

Diffstat:
pp.cc
 | 
89
+++++++++++++------------------------------------------------------------------
1 file changed, 14 insertions(+), 75 deletions(-)
diff --git a/pp.cc b/pp.cc
@@ -63,84 +63,23 @@ static void compute_horizons(
 	}
 }
 
-// CCW winding points towards the camera
-static v3 triangle_normal_ccw( v3 a, v3 b, v3 c ) {
-	return normalize( cross( b - a, c - a ) );
-}
-
-static v3 normal_at_point( const array2d< u8 > heightmap, size_t x, size_t y ) {
-	v3 bent_normal = v3( 0 );
-
-	/*
-	 * A vertex looks like this:
-	 *
-	 *      +y
-	 *   \ 6 |
-	 *    \  |
-	 * 5   \ |  1
-	 *      \|
-	 * ------X------ +x
-	 *       |\
-	 *    2  | \   4
-	 *       |  \
-	 *       | 3 \
-	 *
-	 * We consider up to six triangles for the bent normal
-	 */
-
-#define P( x, y ) v3( x, y, heightmap( x, y ) )
-	if( x > 0 ) {
-		if( y > 0 ) { // bottom left
-			v3 tri2a = P( x, y );
-			v3 tri2b = P( x - 1, y );
-			v3 tri2c = P( x, y - 1 );
-
-			bent_normal += triangle_normal_ccw( tri2a, tri2b, tri2c );
-		}
-		if( y < heightmap.h - 1 ) { // top left
-			v3 tri5a = P( x, y );
-			v3 tri5b = P( x - 1, y + 1 );
-			v3 tri5c = P( x - 1, y );
-
-			v3 tri6a = P( x, y );
-			v3 tri6b = P( x, y + 1 );
-			v3 tri6c = P( x - 1, y + 1 );
-
-			bent_normal += triangle_normal_ccw( tri5a, tri5b, tri5c );
-			bent_normal += triangle_normal_ccw( tri6a, tri6b, tri6c );
-		}
-	}
-
-	if( x < heightmap.w - 1 ) {
-		if( y > 0 ) { // bottom right
-			v3 tri3a = P( x, y );
-			v3 tri3b = P( x, y - 1 );
-			v3 tri3c = P( x + 1, y - 1 );
-
-			v3 tri4a = P( x, y );
-			v3 tri4b = P( x + 1, y - 1 );
-			v3 tri4c = P( x + 1, y );
-
-			bent_normal += triangle_normal_ccw( tri3a, tri3b, tri3c );
-			bent_normal += triangle_normal_ccw( tri4a, tri4b, tri4c );
-		}
-		if( y < heightmap.h - 1 ) { // top right
-			v3 tri1a = P( x, y );
-			v3 tri1b = P( x + 1, y );
-			v3 tri1c = P( x, y + 1 );
-
-			bent_normal += triangle_normal_ccw( tri1a, tri1b, tri1c );
-		}
-	}
-#undef P
-
-	return normalize( bent_normal );
-}
-
 static void compute_normals( const array2d< u8 > heightmap, array2d< v3 > normals ) {
 	for( size_t y = 0; y < heightmap.h; y++ ) {
 		for( size_t x = 0; x < heightmap.w; x++ ) {
-			normals( x, y ) = normal_at_point( heightmap, x, y );
+			float x_plus_one = x + 1;
+			float x_minus_one = x - 1;
+			float y_plus_one = y + 1;
+			float y_minus_one = y - 1;
+
+			if( x == 0 ) x_minus_one = x;
+			if( x == heightmap.w - 1 ) x_plus_one = x;
+			if( y == 0 ) y_minus_one = y;
+			if( y == heightmap.h - 1 ) y_plus_one = y;
+
+			v3 tangent( x_plus_one - x_minus_one, 0, heightmap( x_plus_one, y ) - heightmap( x_minus_one, y ) );
+			v3 bitangent( 0, y_plus_one - y_minus_one, heightmap( x, y_plus_one ) - heightmap( x, y_minus_one ) );
+
+			normals( x, y ) = normalize( cross( tangent, bitangent ) );
 		}
 	}
 }